Introduction: Building and Improving the Harbor Freight 6x8 Greenhouse

Picture of Building and Improving the Harbor Freight 6x8 Greenhouse

The 6x8 Harbor Freight greenhouse kit can be a true bargain with its $299 price tag and an always-available 20% off coupon making it the least expensive aluminum framed/polycarbonate paneled unit on the market.   But the entry level cost brings with it some challenges which are well documented on a number of gardening sites.   These challenges include:

1) Owners report premature deterioration of the polycarbonate clear plastic panels in hot/sunny climates such as Zone 9a where I live.   Harbor Freight claims the panels have UV protection but many owners have questioned this assertion based on rapid discoloration, brittleness and pitting of the panels.

2) The aluminum frame pieces are thin and the unit is flimsy and unstable during construction making it very difficult to assemble by just one person.   Even when finished, the unit is somewhat flexible and susceptible to damage in light and moderate wind or rain.   The manufacturer even stipulates the unit should be erected only in areas “sheltered from the wind”.

3) The 6x8 unit has minimal headroom inside (approximately 6' at the peak) and the doorway is just 5'4" tall making it difficult or uncomfortable to enter and exit.

4) The unit comes with a sliding door rather than a hinged door.  Owners complain the slide mechanism often jambs and that the door can be blown off the tracks in light to moderate winds.

This Instructable demonstrates how these problems can be reduced or eliminated by:

1) Covering the questionable polycarbonate panels with high quality UV protected 6 mil plastic film. (Cost approximately $60)

2) Building a rigid 2x4 framework of benches and shelving which doubles as a solid interior structure for anchoring the aluminum framework during construction and for providing ongoing stability.  (No additional cost assuming benches and shelves are already planned.)

3) “Raising the Roof” of the HF unit nearly a foot by using 2x12's set on edge for the greenhouse’s base.   (Little or no additional cost compared with alternative “foundation” systems described in the construction manual.)

4) Reconfiguring the stock door so that it is solidly hinged to the framework rather than operated as a flimsy slider.  (Cost approximately $20 for hinges, latches and weatherstripping.)

The tools and materials needed for these improvements will be identified in the individual steps which follow.   One cautionary note, the assembly instructions which come with the HF greenhouse are notoriously difficult to follow.  The good news is there are a number of owners on the web who have documented their builds and provided helpful tips for deciphering the directions.   With just a bit of searching around you will be able to locate these references and eliminate a lot of frustration during the assembly.

One other consideration to keep in mind.  In addition to the additional $80-$90 in cost for upgrading your HF unit, these improvements are somewhat time consuming, particularly the application of UV resistant film to each polycarbonate panel.  I would estimate that at least 16 to 20 additional hours are needed to build the unit as described below versus erecting the unit in stock fashion.   For some people it may be worth it to step up to a more expensive greenhouse kit that includes panels with established UV protection.  

Step 1: Constructing the Base

Picture of Constructing the Base

A)  Lay out 4 foundation piers.

The HF greenhouse can be built on any number of “foundations”.   I chose to erect mine using the 4-pier technique but other foundations are just as effective and directions for laying out various foundations are provided in the assembly instructions.   Whatever foundation you use, just make sure it is level and will allow you to lay out the base sills perfectly square.   Concrete piers are available at almost any building center such as Lowes, Home Depot, or Menards.  I prefer the type with the wood block attached to the top rather that those with metal straps but either will work.

B)  Cut 2x12 base sills.

The four sides of the base are made of 2x12 treated lumber set on edge so they stand 12" high.  These pieces must be cut to exact length based on the four aluminum base pieces (marked #s 16,17,34 and 34 in my particular kit) that come with the HF unit.   The HF assembly instructions say the outside dimensions of the wood sill framework should be 75" x 98 ½" but after many measurements I determined it needed to be 74 ½" by 98 5/8".   To achieve these dimensions I cut my front and back sill pieces at 74 ½" and my two side sill pieces at 95 ½".  Do not use these  dimensions, however, until you have laid out and measured your own aluminum frame.

Before assembling the wood sills, make preliminary door cuts in the front 2x12 sill (the one on the entry door side of the greenhouse).    Later on in the construction you will be cutting the entire doorway opening out of this 2x12.   But for now make a 3"-4" deep cut on each side of where the door opening will be at both the top and bottom of the 2x12.   The will keep the 2x12 intact during fabrication but will make it much easier to saw out the opening once everything is together.    The doorway opening can be located by temporarily bolting the aluminum doorway supports (pieces identified as #6 and #7 in my particular kit) to the aluminum base piece (# 17 in my kit).   Mark the aluminum base piece (# 17) on the inside edge of the doorway support.   This location can then be transferred to your 2x12 sill piece for cutting.    For added strength and to make sure things stay square and level, a treated 2x4 is screwed to the bottom edge of the front (door side) 2x12 sill piece.

C) Assemble the base sill pieces.

Reinforced angle brackets (I got mine at Home Depot) are used to attach the 2x12 sill pieces to the 4 piers.  Make sure the sill pieces are absolutely level with one another and square.  If these precautions are not taken, the aluminum framework will not go together properly and the pre-drilled holes in the framework will not line up...making for MUCH frustration.  So take your time and get it square and level.  The 2x12 sill pieces can be fastened together at the corners with nails although I prefer to use 3" decking screws.  The four aluminum base pieces from the kit (#s 16, 17, 34 and 34) can then be temporarily assembled and clamped or screwed  on the four 2x12 sill pieces.

Step 2: Support Structure (Benches and Shelving)

Picture of Support Structure (Benches and Shelving)

A)  A 48" long 2x4 is screwed to the inside of the base at each corner.  Use a level to make sure the 2x4's are perfectly vertical in each plane.   I used treated lumber throughout the interior construction but common lumber would suffice since it will have minimal contact with the elements.

B) Add a 75" vertical door post and horizontal bench support.   Then, using 2x4 material, construct the center bench/shelf support and similar support at the opposite end of the greenhouse to the height and width you want for your shelves.  My top shelf is 48" above the floor and 24" wide but you can build to suit your own needs.

Step 3: Aluminum Framework

Picture of Aluminum Framework

A) You can now begin to assemble the aluminum framing pieces following the directions in the greenhouse kit.   The aluminum pieces are fastened at various points to the 2x4 bench/shelving structure with 1" round head screws in order to stabilize the framework . To keep the aluminum pieces square and vertical, wood spacers are used between the 2x4 structure and the aluminum framework.   For the most part, quarter inch redwood slats (also known as bender board) can be used for this task.  You may have to cut spacers to make a more exact fit in some situations.  Once the aluminum framework is completed and all the components are square and plumb, you can permanently attach the four aluminum base pieces (#s 16,17,34 and 34) to the 2x12 sills using 1" screws.

B) This step is not required but I installed a 4x8 sheet of foil faced 1" insulation on the north wall of the greenhouse.  I am also making my “floor” out of washed stone over weed-resistant landscape fabric.  Owners can choose any sort of flooring they desire.

C) There are a number of points where the bolts for the aluminum framework will protrude into the 2x4 framework.  To keep everything lined up properly either drill out the area behind the bolt or use a chisel to remove enough wood so the bolts are not impeded.

Step 4: Opening Up the Doorway

Picture of Opening Up the Doorway

When the aluminum framework is complete, use a saber saw or reciprocating saw to cut through the aluminum base plate and finish the cuts you made earlier in the front 2x12 sill to open up the doorway section.  You can also use an angle grinder, as I did, with a metal cutting blade to cut the aluminum base piece.   The final photo shows what your structure should look like at this juncture.

Step 5: Benches and Shelves

Picture of Benches and Shelves

I used wire shelving (available at hardware and building centers) for the benches and shelves.  You can use wood but the wire shelving creates fewer shadowed areas which reduce sunlight to the plants.    The top shelf is two side-by-side units each 12" wide.  They rest on 2x2's which are screwed to my 2x4 framework for support.   To allow the shelving to sit level, a 5/8" wide groove must be cut down the center support for the main wire rods to fit into.  I cut this slot with a dado blade on my table saw.   If you do not have that equipment, you can use two 2x2 supports instead, one on each side of the metal rods.

Step 6: Apply the UV Resistant Skin.

Picture of Apply the UV Resistant Skin.

Each clear polycarbonate panel in the HF greenhouse kit will be covered on the exterior side with 6 mil UV resistant plastic.  (Note: I did not cover the 4 panels on the north side of greenhouse which are protected from the sun by the foil faced insulation.)  This is a greenhouse grade material guaranteed to hold up under intense sunlight for at least four years. It is available from a number of different web sources.  I purchased mine from the Greenhouse Megastore because they sell it in smaller quantities.   My 12' wide x 25' long roll was more than enough to cover the HF unit and cost approximately $55 including shipping.

I cut each piece of plastic film to the exact same size as the polycarbonate panel.  The film is secured to the panel with Nashua 322 HVAC foil tape which can be found in or near the plumbing/vent pipe section of most building centers such as Home Depot.  A roll of 150' is about $8 and should be enough for one 6x8 greenhouse.    The tape is 2" wide and we will be cutting each piece it in half lengthwise during the application process. 

To attach the UV film to the panel, first peel off the protective plastic coating on each side of the HF panels.   Lay the UV film on top of the panel and clamp it in place to keep it in position.   Draw a line (see arrow in photo) across the end of the UV film approximately 3/8" from the end of the panel.  A Sharpie Ultra Fine Point permanent marker works fairly well for this purpose. 

Cut a piece of foil tape to the same width as the panel and then cut the tape in half lengthwise.  This will give you two pieces of foil tape each about 1" wide.  Mark the tape to keep track of which is the cut edge and which is the original straight edge.   Peel back about the first 6 inches of protective paper on the back of the foil tape and carefully align the uncut original straight edge of the foil tape with the line you have drawn on the UV film.  Press the foil tape to the film and then continue to apply the film, pulling back the paper backing about 3-4 inches at a time and then pressing it to the UV film using your line as a guide.  As you do this, you should have about ½" of tape extending out over the end of the panel.  Take your time applying the tape but note that no matter how hard you try, the tape will not lay perfectly flat without some wrinkles and imperfections.  So no need to shoot for perfection.

Starting at the center of the panel and moving outward, fold the foil tape over the end of the panel and press it firmly against the back side of the panel.  Do not try to stretch or pull the UV film tight.  Unfortunately, there will be wrinkles and fold marks in the 6 mil film as it comes from the supplier and they are virtually impossible to remove.  If you pull the film too tight it can cause problems later on because the UV film contracts much more rapidly than the polycarbonate panels once they are under direct sunlight.  If the film is too tight it can actually cause the polycarbonate panels to bow up or result in stretching and deterioration of the film and  foil tape.   Granted, it doesn’t look the greatest, but at least some of the wrinkling will be reduced once the film has been in the sun for awhile.

Continue applying foil tape on all four sides of the polycarbonate panel.  Once all the tapes are applied, select the bottom edge of each panel (some panel shapes have a natural bottom edge and some you just choose the bottom edge) and using any sharp instrument, poke holes through the bottom edge of the tape every 2-3 inches so that any moisture which might accumulate in the panel channels can “weep” out the bottom. 

Install the completed panels in the greenhouse framing using the clips as shown in the HF instruction manual.  Although I haven’t done it yet, many owners recommend putting screws directly through the polycarbonate panels and running the screws into the aluminum framework.   With the 2x4 interior framework shown above, the polycarbonate panels can be screwed to this woodwork for additional strength and to prevent the panels from being blown out in heavy winds.  If you do this, use screws with plastic or rubber washers (typically used for metal pole buildings or corrugated fiberglass panels) which seal on the outside against rain and moisture.

Step 7: Attach Hinges to Door.

Picture of Attach Hinges to Door.

A) Put together the aluminum door frame following the instructions in the HF manual.  Do NOT install the door hanging hardware (pieces labeled 14 & 19 in my kit).  Remove the rubber seal which will most likely be pre-installed on each side of the door frame.  The seal can be easily pulled out of the channel from either end.

B) Attach three hinges to the left hand side of the door frame.   I used Everbilt “Narrow Utility Hinges” (shown in photo) which are about 3/4" wide and 2 ½" tall.   The door frame itself has a small channel milled into the aluminum and a spacer is required so that the hinge will lay flat.  I discovered that 3" mending plates (available at building centers or hardware stores and shown in photo with hinge) are the exact right depth for this purpose.   Unfortunately, the hole pattern on the mending plate does not match the hinge so the plate must be re-drilled to match the hinge.  This can be done by clamping the plate to the back side of the hinge and then using a drill press or just a common electric drill to create matching hole patterns. 

The mending plate can then be clamped to the door frame and used as a guide for drilling matching holes in the door.  I put one hinge half way up the door and the other two hinges about 3 inches from the top and the bottom of the door.   The hinges are bolted to the door frame using ½" long #8 bolts and nuts. 

Before hanging the door, cut off the small plastic tabs which protrude from the bottom of the door.   These are guides used to keep the sliding type door in the bottom track and will interfere with the door being opened when using a hinged configuration.  

Step 8: Attach Door to Greenhouse.

Picture of Attach Door to Greenhouse.

If you have already installed them, temporarily remove the polycarbonate panels which are to the left and right of the door opening to give yourself some working room.  Position the door square on the aluminum door framing and clamp it in place.  Make sure the bottom of the door is even with the bottom of the framing side pieces (#s 6 and 7) to insure it will open and close properly.  Swing the hinges so they are against the outside of the aluminum framework around the door opening.   Using the hinge holes as guides, drill mounting holes through the frame.   On my installation, the hinges did not lay quite flat against the framing.   And if you install a spacer behind the hinge it can interfere with installation of the polycarbonate panel.  I simply left this slight angle in the hinge installation and the door works fine.  Attach the hinges with #8 bolts and nuts.  After all the hinges are bolted up, test the door to insure it swings freely and remains lined up with the surrounding framework.

Step 9: Install the Latch.

Picture of Install the Latch.

To make the door latchable, the center panel of the door needs to be reinforced a bit.  I used 1/4" Marlite and bolted it to the inside surface of the aluminum cross braces. The UV covered  polycarbonate panel is then installed in its normal position on the outside of the Marlite.

To latch the door you can use almost any screen/storm door hardware available at home centers (Lowes, Home Depot etc.).   I happened to use Wright Products model #V670WH which costs around $10.   The HF greenhouse door is much thinner than normal screens or storms so a 3/4" redwood spacer board was cut, drilled and mounted behind the doorknob.  The inside handle is mounted as the directions provide. The latch is bolted to the aluminum framework using #8 bolts and nuts.   The completed door is shown in the photos from the outside and inside.

Step 10: Fill the Void.

Picture of Fill the Void.

Since our new door sits about 12" higher off the ground than the original, we have a rather large gap left open at the bottom of the door.  We want ventilation anyhow, so this gap is covered with two layers of 6 mil UV film.   The film is slit approximately every 3 inches and the slits are offset to reduce air flow.

Step 11: Enjoy Your Greenhouse Gardening.

Picture of Enjoy Your Greenhouse Gardening.

Your Harbor Freight greenhouse should now be ready for many years of growing in the sun.


ChrisK327 (author)2017-01-29

Built this for my dad 4 years ago. The bolts that slide into the channels are starting to fail. The head separates from the threaded part which then falls off. Observed anything like this??

LineaS (author)2015-10-13

Thanks so much for posting these great improvements. I have bought greenhouse and want to know how the plastic covering on the panels is holding up after three years. I plan to do the same thing on mine.

dewey302 (author)LineaS2015-10-13

I am very happy with the UV resistant plastic covering which has been in place for over three years now. I must add the caveat, however, that I keep the southern and western sides of the greenhouse covered with shade cloth (Home Depot type shade material). I started doing this after I discovered that the intense sunlight here in Central California could easily bake my plants if I wasn't very careful. I started putting up the shade screen just during the summer months but I've kept it in place year round for the past two winters. This shade seems to actually help my seedlings during their early weeks by tempering the amount of direct sunlight. The plastic on the east and north sides of the greenhouse are not protected with shade screen and I can not see any evidence of degradation at all...none of the usual brittleness that you'll find with common plastic sheets. The HF panels themselves still look like the day they were installed. "Cliff Notes" answer to your question --- Seems like a good investment of time and money.

LineaS (author)dewey3022015-10-13

Thanks so much, have plastic, will apply! Fortunately no shade cloth required here, have shade in afternoon. Again your info has been great!

waterstar (author)LineaS2016-04-13

How do you apply the extra plastic over the panels? Should we put it on before or after we put the panels in?

Thanks in advance...any hints are so helpful

dewey302 (author)waterstar2016-04-13

Apply the UV plastic as shown in Step 6 of the Instructable.

waterstar (author)LineaS2016-04-13

How do you apply the extra plastic over the panels? Should we put it on before or after we put the panels in?

Thanks in advance...any hints are so helpful

waterstar (author)LineaS2016-04-13

How do you apply the extra plastic over the panels? Should we put it on before or after we put the panels in?

Thanks in advance...any hints are so helpful

Froptus (author)2016-03-25

Very nice guide. Thank you for posting it. One question: You said that before applying the UV film that one should remove the film that comes already on the panels. Isn't that also a UV film? Can't I just install on top of that?

dewey302 (author)Froptus2016-03-26

My understanding is that the film on HF panels is only for protection against scratches and damage during shipping rather than a UV protective layer. I have also used high quality UV resistant panels for other projects. These come with a plastic film as well but it's purpose is to mark the outer (UV protected) side of the panel as well as protection during shipping. On higher quality panels, the UV protection is a part of the plastic itself, not a thin sheet over the top.

diverdale made it! (author)2016-03-22

This was a great guide. I did my shelving a little different but followed the rest and am finishing up my Wife's greenhouse now. She says thanks! ;) Just need to finish up the door. I'm also running some 110 outlets from my workshop solar setup.

dewey302 (author)diverdale2016-03-22

Looking good.

Adrewry (author)2016-01-10

does anyone know what kind of heater I can use in this 8 x 6

dav3id (author)Adrewry2016-02-01

I use strings of the older Xmas lights underneath each shelf, which applies gentle heat to the root zone of the plants. They are cheap at surplus/salvage stores; each of the strands runs 10-15W and can be strung together to conserve outlets. Temperature controls can be found at most grow shops, or online depending on how much heat you need and your budget.

Nice Instructable, I did something similar with my unit but instead of 2x12 I used three courses of 6x8x16"" cinder blocks, I also dug out the interior 10" or so before adding the gravel for the floor, it gave me another ~8" of head room.

dewey302 (author)dav3id2016-02-01

I like your innovation of using lights. They could even be put on a little thermostat so they only come on when the temps dip to a certain level. And being close to the soil, they would take a lot less total energy than trying to heat the entire greenhouse. Might have to do some shopping...

RonB65 (author)2016-01-24

Great article. I ran across a kit for the HF 6x8 greenhouse that had been given to my mom years ago but never assembled. I'm going to elevate it as you did and build the shelving system as extra support and hinge the door. What I think I will be different than you however is to use 2 additional piers on either side of the door opening rather than just relying on a 2x4. In time, even treated wood will rot in contact with the ground.

RonB65 (author)RonB652016-01-25

One othe thing that I am doing different as well. Since I will need spacer between the corner and wall studs and 2x4's to be able to screw to the 2x4's I'm gong to cut an 8 foot long furring strip the thickness I need to fill that gap and run it all the way across the inside of the wall halfway up. I will then drill and screw through the studs, the furring strip and into the 2x4, but I will also drill trhough and screw each polycarbonate panel to the furring strip eliminating any possibility that they can blow out. I'll also run furring strips along each side of the ceiling and do the same. I'll just bolt the ceiling furring strip directly to the aluminum framing. The panels on the front of the greenhouse can be drilled and bolted through the aluminum horizontal wall support.

Adrewry (author)2016-01-10

Does anyone know what kind of heater I can use in this 8 x 6 greenhouse?

cjm15 (author)2015-12-27

dewey are you still on here??? !!!

dewey302 (author)cjm152015-12-29

Yes I am.

Vince B (author)2015-10-12

Dewey - I'm working on my HF greenhouse now. Tryin to get outside dimension measurements. How are the aluminum base pieces supposed to butt against each other from one of your photos it appears the inside corners of the base touch. Is that right. If so my measurements are 99 x 73 5/8.

Touch E

dewey302 (author)Vince B2015-10-12

Yes the inside corners of the base pieces touch, the they do not overlap. At least that is the way mine seemed to want to go together. Regarding the measurements, I'm assuming you are figuring out the outside dimensions for the wood foundation. I just measured mine and the foundation is 74 1/4 x 98 3/4. But I wouldn't worry too much that our dimensions don't match up exactly. Mine is over three years old now and I'm not at all certain the folks who make these for HF keep the same measurements for the pieces over the years. In fact, I'm not even sure our two units would have been made by the same mfr. Lay it out with the inside corners touching and that should be good for doing the foundation pieces.

chris.york.56 (author)2015-04-19

I wish I had seen this BEFORE I built my greenhouse. The instructions are pretty sketchy. My biggest complaint is the dimensions for the foundation being wrong. I built the foundation and assembled it making sure it's all square only to find out the foundation is 1/2" too wide! Arggghhh!!!

I would have measured my frame and built your 2X12 foundation design - that's a great improvement. I will build shelves like yours - looks great! The door is flimsy but seems workable - we'll wait and see. These are excellent ideas and plans - anyone considering should go for it!

DarrellG (author)2015-04-12

Ray W (author)2015-02-18


Great write up. Packed with a lot of smart improvements. I'm waiting for my HF 6 x 8 to be delivered, and was just doing some research. I believe I owe you, because I'm sure you saved me a ton of frustration. Once things thaw here in the Midwest I'll start the build, at least with what I've learned here I can start assembling supplies. Thanks for the great info.

speedoo.mcfadden (author)2015-01-30

Hi, I've had my 6X8 HF greenhouse for about a year now. The sliding door is a little sticky, but nothing I can't deal with. My problem is that, in high winds, the individual panels blow out of the frame and end up in my neighbor's yard! No matter how many of those little spring clips I use to secure the panels, they keep blowing away. I've lost quite a few spring clips this way, although often the clips are still attached to the frame when the panel goes missing! Does anyone else have this problem, and can anyone suggest a solution? I've considered drilling holes in the panels and screwing or wiring them to the frame, but I'm afraid if they continue to blow away, this will just tear holes in the polycarbonate, making the panels unusable. I mounted my greenhouse on a 4X4 wooden frame secured to the ground with 2' rebar, so I'm not worried about the whole thing blowing over; just the individual panels. I just know I'm eventually going to lose one or more. Thanks for any suggestions!

I've read of a number of folks who have trouble with panels blowing out. Some people do screw them in place. Others use screws and silicon. I've never heard of the panels blowing out once screws have been installed be there is a first time for everything and your concerns are not out of place.

Another trick I have heard people use is the mount additional support members on the inside of the structure about half way up on the panel and then screw the panel to those supports as well. I'm thinking this may be why I haven't (yet) had the problem of blown out panels since we do get some pretty high winds here in the central valley. I built quite a bit of structure on the inside of my greenhouse which doubles as shelving support. I think this may keep the panels from bowing and flexing in the winds. I believe this is the primary cause of panels losing panels in the wind. If the center of the panel can't bow or flex, I don't believe it will get blown out of the framework. Hope you find a solution.

hogthrob (author)2015-01-26

Great 'ible I have a similar framed green house that is evolving...

Started off as glass which blew out (created an interesting glass shard installation on my neighbours lawn) so I replaced it with polycarbonate panels. I dont have such an issue with UV in Yorkshire but I know they are only UV on one side which is probably the issue with early degradation when they are fit backwards. Mine is raised up on cinder block foundations to get the extra height.

Next step is to silicon the panels in. Over xmas we have had 3 high winds which spread the green house around my neighbours gardens. I will let you know if it works.

RadyStefanov (author)2014-06-30

Hi Dewey,

First, thank you for your article, I took most of your ideas in building my greenhouse, and I love it.

I also saw how you use shade cloth to protect from the heat. Can you tell how well does the shade work, or maybe it does not? Did you remove the panels completely before putting the shade cloth? Do you think it is important that shade cloth goes all the way down to the wood? I placed some shade cloth and removed most side panels, but there is not enough ventilation, so the temperature inside gets higher than outside. Trying to figure out how to deal with the Texas heat.

One more question. Have you thought about updating your article, after all this time? Perhaps there are new ideas you can share, or things that, looking back, you could have done differently?

dewey302 (author)RadyStefanov2014-06-30

In my opinion, the shade cloth does a terrific job. My guess is your Texas heat might be similar to here in the CA Central Valley. Even in the middle of winter, the sun can get very intense. So I leave my shade cloth on year round. My seedlings do pretty well in that amount of shade even in the late winter/early spring. And during the summer it is a necessity unless I opted to put in a lot of expensive fans and vents. My inside temps do go above outside temps but NOT outside temps in the direct sun. My feeling is the ambient temp is not the's the temperature in the direct sun that will do in the plants.

During the spring, summer and fall I have the door open at all times and I remove the panel on the wall opposite the door. I also totally remove the two roof vent panels. I keep all the other panels in place. I wouldn't think the shade cloth needs to go down all the way to the wood unless you have low plants sitting down there at floor level. If you can, I'd cover all the way to the wood. But not absolutely necessary.

Your suggestion of updating the original article is a good one. There have been some good questions and suggestions in the comments section and some minor changes I have made (like the shade cloth) that more readers would see if I summarized them in the original. Now I just need the time to do the re-write.


ablue5 (author)2014-05-08

Hello Dewey,
I have 3 questions. Would you recommend using composite wood rather than red cedar to keep rotting to a minimum?

Did you have a system in play for automatic watering or misting?

Did you have lighting.. fans or heat/cooling?

dewey302 (author)ablue52014-05-08

I used treated lumber for the base and shelving supports. I'm no expert, but I would think composite wood might be the least preferable choice due to potential rotting and glue failure resulting from high temperature fluctuations and possible UV rays. Cedar would be a nice choice but might be pricey depending on your location.

I don't have any automated watering or misting. I do both by hand. I have a wide variety of plants (from tiny seedlings to full size lettuce) at any one time and I move plants in and out almost daily depending on their size and maturity. I also shuffle them around on the shelves depending on their light requirements. So an automated watering system would be a challenge for me unless each drip/feed hose had an individual valve to regulate the water flow to the various plants that would be in any particular position in the greenhouse. But an automated misting system would be a very nice addition since all my plants could use a spritzing now and then.

I don't have inside lights but it just so happens I built my greenhouse about 5 feet from our cabana, and the cabana has a number of perimeter lights which provide more than adequate illumination if I want to work after dark. Also keep in mind, your local building code may require you to obtain a building permit if you install electricity or running water inside your greenhouse (ours does). And in some localities, that can be a major headache. I also do not use fans or mechanized cooling. As I noted in another post (including a photo) I keep my greenhouse covered with shade cloth year round. I also remove the window panel opposite the door during the summer and I keep the door open as well. I also remove the two roof windows during summer months. For the simple flowers, trees, bushes and veggies I grow, this seems to provide adequate growing temperatures in spite of the intense heat/sun here in the Central Valley of CA. BTW, I also don't heat during winter months. We do get frost here, so I'm still learning which plants will survive and which won't. For my really early seed starts...I do everything in our house under grow lights.

waterstar (author)2014-02-20

Excellent post. Also like your post on the sliding barn doors. THANKS.

Can I make the greenhouse 2 feet taller by using another type support?

dewey302 (author)waterstar2014-02-20

I would think so but I've never tried it so I don't know what complications you might encounter. You might have to reconfigure the door a bit to reduce its overall height to 7' or less otherwise it might get a little floppy. Keep in mind the aluminum framework with the kit is very thin and light so any structural support you can incorporate into your design is going to be a real plus.

adrenalynn (author)dewey3022014-04-20

Hi Dewey, appreciate your 'ible here!

I had one of these gifted to me, I'd been toying with buying one for quite a while. I have a pre-existing 10' x 12' level concrete pad (it had another structure on it) - I'm contemplating using stacked concrete blocks to raise it up 16" around the perimeter of the greenhouse frame. Concrete block for me would come out to ~$65, versus double that for 2x12 treated lumber. I'm considering leaving the door intact, a 16" step-over height for me wouldn't be the end of the world, and gives me a cooler zone down at the bottom. I could, of course, cut the block, but if I leave the frame intact, it'd probably make it a bit simpler to disassemble the next time I (ick!) move.

Anyway - it's sitting in its carton out back on the pad, I'm overwhelmingly tempted to go put it together, but I really should wait until I can borrow a friend's truck and go get some block.

Appreciate any thoughts you might have!


dewey302 (author)adrenalynn2014-04-20

In figuring your costs (block vs treated lumber) be sure you include a "sill plate" if using blocks. You need to have a way to secure the greenhouse frame to a sill plate and then secure the sill plate to the blocks. Or in the alternative, you need a means to secure the frame directly to the block.

Regarding the "step over" entry door I guess this comes down to personal taste and your willingness to put up with stepping over the blocks each time you enter or exit. I know I would get frustrated with a step like that very quickly. But then that's me. Just give it a good long "think" before you go that route.

BTW - I envy you getting one of these as a gift. Should be fun.

adrenalynn (author)dewey3022014-04-20

Hi Dewey, thank you for your considered and quick reply!

"When I have money, I don't have time. When I have time, I don't have money" - story of my life. I'm in one of those crossing cycles at the moment. ;-) My projects tend to outgrow my [non-existent] budget entirely too quickly.

Our weather is pretty mild here (Sacramento, CA), some strong winds rarely in the winter, but I'm pretty insulated in that small back yard w/8' plank fence.

My plan was to lag a small piece of 2x4 scrap inside the block every couple feet, then screw the frame directly down to it. If the greenhouse still lifts, it's probably sited wrong at that point, since there's nothing for the wind to "get under".

Step-over: you may end-up correct, fortunately that's one I can remedy at any later time. Angle grinder will cheerfully cut that block as well as the aluminum sill, so that leaves me time to reengineer the door at my leisure. The big thing is to get it up and planted before the season gets much later. Not raising the house now is something that's difficult to correct in the future after it's constructed - if that makes sense.

I do the odd electrical engineering work, and sent my client to HF to pick up a few bits for the job I was doing for them. They know I've been coveting that little greenhouse since before moving into this house, and they picked it up for me as something of a "tip". Very considerate! They even dropped it off at my house and helped me carry it back to the pad.

16" lift (rather than 12" 'nominal') feels more like what I'd want, as I really want to play with hydroponic lettuce and other leafy growing, and vertical density is important to me.

Anyway - I do really appreciate your input, and that you took the time to put this 'ible together! Thank you so much again!

dewey302 (author)adrenalynn2014-04-22


I'm not too far down the road from Merced/Atwater. Being in the Central Valley I think you might want to plan on one further addition to you greenhouse. Shade. I keep my greenhouse covered with shade material (comes in rolls at HF or Lowes) year round. I discovered (sadly) very early that the intense sunlight here in the valley can toast your plants in no time flat. I have attached the shade cloth with simple plastic clamps that I buy by the dozens in bags at HF or other big box stores. I also keep the door open permanently from about March-October and remove the center panel on the opposite end from the door during those same months to provide more natural air movement through the "shadehouse". I've attached photos of the outside and inside of the greenhouse showing the shade cloth attached.

adrenalynn (author)dewey3022014-04-22

Here's the site, as-seen by one of my cctv cameras. Notice the pad at the far end of the photo (with a set of ladder legs on it, and the Harbor Freight box laying across it).

adrenalynn (author)dewey3022014-04-22

Thank you again, Dewey!

I'm sited under a large Live Oak. I get about 4hrs in the early morning and 3 hours in the evening of sun there in the summer, but it's wide open in the winter. Door is to the south. I have a couple of shade sails that I figured I'd take from the oak to the ground on each east/west side, so I can roll them up and down - maybe even automate.

Your work is so pretty and clean! I'm impressed with the craftsmanship and preplanning. Wire Shelving is "ClosetMaid" isn't it? I built that out in my closet (shoeeees!) a few years ago, looks familiar. :)

After our discussion, and rereading your 'ible here, I got to thinking that I might drive strongties into the pad, bring the 2x4's up at the frame up rights through the cinderblock (as previously discussed) and then dump some quickcrete into the block. That would tie the 2x4 to the pad, and stabilize it through the block, and then I could just lath-screw the whole frame to the 2x's. Incremental cost is negligible that way.

Have you considered a mister in there? I was contemplating tossing together a 1/2" mister running the entire length at the frame peak, front-to-back. (we get pretty dry here in the summer, as do you, and that airflow you describe through the mist would definitely help the plants "sweat" instead of broil)

I had also been contemplating a box fan in a custom panel at the front and back.

Have you managed to extend your growing season to year-round?

Thanks again for the chat!

waterstar (author)2014-03-21

Where did you find the " high quality UV protected 6 mil plastic film. (Cost approximately $60)"?

dewey302 (author)waterstar2014-03-21

Details regarding the UV film can be found in Step 6 of the Instructable. As noted there, I got mine on line from the Greenhouse Megastore.

waterstar (author)dewey3022014-04-22

Thank you. Also, is there a reason the ceiling/roof does not be covered or did you do that and I misunderstand?

dewey302 (author)waterstar2014-04-22

As noted at the very beginning of step 6, ALL panels are covered with the UV film EXCEPT the four panels that make up the north wall of the unit. So yes, the roof is covered. Sorry if that wasn't clear.

waterstar (author)dewey3022014-04-22

Ok, that makes sense. Thanks so much for all of your time and patience.

pampero (author)2014-03-30

Thanks> good!!!!

waterstar (author)2014-03-22


cjankauski-clemmens (author)2014-02-06

Thank you so much for posting this. I'm hoping to get my greenhouse in a couple weeks but living in central will have to wait some time before we thaw out to assemble it. We've had a nasty winter this year and our summers usually are quite hot and a few tornadoes too. lol

I've always been pretty good a assembling things but nothing of this scale so i'm quite scared actually. But I knew from the reviews that this would need some strengthening. Am wondering though can I still do the shelving without raising the greenhouse?

I'm hoping to get a parts list together for the lumber, shelving and hardware together in the next couple weeks. Thanks, Cindy

You can put shelving in without raising the entire unit. You should be able to design it so that it will attach to and strengthen the aluminum framework. Have fun with your build.

Thanks :)

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