Build a Floating Deck

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About: I got an old sewing machine when I was just a kid, and I've been hooked on making stuff ever since. My name is Sam and I'm a community manager here at Instructables.

Here is how I built a deck in my backyard.

It's a "floating deck," which means it simply rests on blocks at ground level, and is not anchored deeply in the ground.

This type of deck can only be made in areas that do not have a deep winter frost. In colder climates, the ground goes through freeze and thaw cycles which result in surface ground upheaval and movement over time, which would ruin all your work in short order.

Building a deck is a lot of work, and it isn't cheap. But it is do-able and you can save a lot of money by doing it yourself rather than hiring it out. The total cost for this was almost exactly $1600 USD. The footings and framing totaled $600 and the decking itself was $1000. Total time spent was over 100 hours during a period of a couple months.

If you're looking to build a deck, this Instructable will give you some ideas for starters but I strongly recommend taking a couple weeks and studying everything you can find before making a plan.

The internet is overflowing with information on how to build a deck.

This is simply how I made mine. Enjoy!

PS: I wrote an instructable on my shed too, if you're interested.

Step 1: Tools

You don't need a shop full of tools to build a deck. Here's a list of what I'd say is essential:

  • saw horses (build some of these!)
  • circular saw
  • measuring tape
  • speed square
  • corded drill - I prefer corded rather than cordless for drilling holes
  • cordless drill/drivers (I have these and LOVE them)
  • level (at least a 4-footer)
  • yard tools: shovel, wheelbarrow, mattock
  • rubber mallet or a tamper

Other things I used, but you may not need:

  • electric planer (I just got this specifically for this project - seems good so far)
  • jig saw
  • table saw

Step 2: Foundation Blocks Layout

The main area of my deck is just a little bigger than a 12-foot by 8-foot rectangle. This worked out well for material usage and produced very little waste.

I began by laying out cement blocks in a 4-foot grid, and spray painted around them to indicate their locations. The blocks I used are "Old Manor" landscaping blocks that I got at Home Depot. Other hefty paver-type blocks would also work.

Each block location was dug about 6 inches deep. I used a pick mattock (like this or this) to remove the earth in a mostly horizontal fashion, just a couple inches or so at a time. The goal is to excavate as much earth as needed while leaving the ground beneath as compacted and undisturbed as possible.

Step 3: Set Blocks

The area where I was laying out the blocks was mostly level, which was nice.

However, it's not critical to place all the blocks completely level with each other.

Just pick the highest looking spot and set that block first. As long as all other blocks are set either level with this one or lower, things work out very well.

I just tried to keep the level of all the blocks within an inch or so, but there's no need to fuss over the precise height of the blocks. Any differences will be made up with shims later on when the deck frame is in place.

To set the blocks, I made sure each hole had all loose earth removed and only hard-packed earth was at the bottom of the hole.

I added a few inches of paver base (basically a mix of jagged rocks, gravel, and sand), and compacted this layer by placing a block on it and pounding it with larger rubber mallet.

The block was removed and a layer of leveling sand was added, and compacted again as described. If I needed to raise or lower the block, more leveling sand was either added or removed. When I was happy with the height, the block got another good compacting with the mallet, and more sand was added around the block to lock it in place.

This was repeated over and over until all the foundation blocks were in place. This step alone took several evenings to complete.

My yard has been well-settled and hard-packed for at least 15 years or more. Since I followed the same procedure for placing each block, any further settling of the foundation blocks should be uniform. Where I live, we do not have a deep winter frost, so using blocks that essentially just rest ("float") on the ground surface is acceptable.

In colder climates, you cannot build a "floating" deck, but must build it on anchor posts that are cemented deep enough in the ground to avoid any ground upheaval (surface swelling and adjusting that occurs as the ground goes through freeze and thaw cycles over time).

Step 4: Build Frame

The area where my main deck frame was going to be was a pretty tight fit, so I built the frame out in my yard and moved it into place once it was complete.

The frame was built with pressure treated 2x6 lumber. The outer frame was fastened together with 2 1/2" exterior decking screws (these).

Joists were hung every 16" on joist hangers (these).

When the frame was built, it weighed several hundred pounds and required a handful of strong people move it into place.

Step 5: Level the Frame

With the frame in place, I used composite shims (these) on all of the foundation blocks as needed to bring the frame into level position.

If you want to add a very slight pitch to the deck frame, say, to direct rainwater away from your home's foundation, now's the time to do it.

To do this, just add additional shims in equal numbers to points along one side to raise it up. Once this high side is at the height you want, add shims to the mid sections as needed to regain the direct support onto the blocks.

I went an extra step and added pieces of 4x4 to the location of each foundation block. These were screwed to the frame with lag screws, and glued to the blocks beneath with landscape adhesive. Probably overkill, but I wanted this frame to be rock-solid.

Step 6: Additional Framing

Along the back of the main deck area next to the fence I framed some extensions to fill in the gap.

These little wings are tied to the fence posts for support, so technically, one could point out that these portions are not actually "floating." (But nobody would do that; this is the internet, where people never nitpick!)

The landing in front of the shed is anchored to it with a ledger board using long lag screws. The shed itself was built on blocks, floating in the same exact manner as the deck.

When the frame was completed I used an electric hand planer to remove any high spots to ensure that the decking boards would lay uniformly flat.

Step 7: Lay Decking

This is where everything starts to pay off.

For decking material I decided to go with one of the slightly lower-end Trex composites. It's still pricey, don't get me wrong, but the cost wasn't very far off current prices for redwood or cedar decking, and I wasn't interested in other alternatives.

There are pros and cons to every option in decking material. Be sure to do your research and decide which trade-offs you prefer.

The decking boards are screwed in place with special composite decking screws that don't require pre-drilling.

If you don't have an impact driver, well . . . it's time to get one! Mine was a huge asset throughout this entire build.

I love my Makita drill/drivers and prefer them over several others I have used.

I chose to not lay landscape fabric on the ground under the deck, and some people may question why I didn't do that. I went without to save a few bucks and a day or so's work.

I sprayed herbicide to kill the small amount of stuff that was growing, and am happy to respray around the edges as needed in the future.

Step 8: Mitered Corners

To make the deck look nice and tidy, I placed cap boards around the perimeter with mitered corners.

This was planned out ahead of time, and necessary framing was added to support these various pieces.

Step 9: Plan Your Cuts!

For the main deck area I was using full 12' boards, so there wasn't a lot of thought required to complete that section.

However, for the smaller sections I had to break the full boards down.

Prior to building anything, I made a very detailed plan and purchased all my materials accordingly.

You'll be paying a high price for whatever decking material you choose, so it's wise to think through all the cuts and carefully decide when to cut what pieces from the boards, and in what order.

Otherwise, you'll likely end up with 9 linear feet of material remaining in three-foot sections, when all you need to finish your project is two 48" boards . . .

I learned this lesson many years ago, and very happily did not make the same mistake while building this deck.

Step 10: Decking

Here's a closer look at the completed decking.

Step 11: Decking

And a few more.

Step 12: Removable Ramp

When I was completed with the deck I had one full 16' composite board remaining.

I used this to build a removable ramp so our bikes, mower, and wheelbarrow can get in and out of the shed without chewing up the edge of the deck in front of the door.

This was framed up with pressure treated boards. It's not fastened to the deck at all, so I can just drag it in place when needed. The rest of the time it just leans on the backside of the shed.

Step 13: Enjoy the Sunset

This was a lot of work, but I'm happy with how it turned out.

Thanks for taking a look!

2 People Made This Project!

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29 Discussions

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techy291

1 day ago

You indicate that the blocks aren't susceptible to the upheaval that occurs in some locations that have a deep winter frost because they are resting on the surface.
I'm in an area that does have a deep winter frost (Canada) - wouldn't they be more susceptible to upheaval in an area with frost....?

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seamstertechy291

Reply 10 hours ago

Yes.

Sorry for the confusion, I will update my wording.

What I meant was:

Where I live, using just blocks in this manner is OK because we don't have a deep winter frost . . ie, the ground doesn't swell, adjust, and move around like it might do elsewhere, where you could not get away with this approach.

In colder climates a deck needs to be tied to anchor posts that are cemented deep enough in the ground to not be affected by ground movement at the surface.

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ALPHANUMERICALCODE

Question 9 months ago on Step 5

Awesome deck! A couple questions:

Some of your joists look like they are not supported by a beam or a block. How do you know if you can get away with floating joists or what the proper number and spacing of blocks/beams are?

Your blocking looks to be in a straight line with no offset for screws or nails. How did you attach your blocking?

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seamsterALPHANUMERICALCODE

Answer 9 months ago

Hi there,

The joists all hang on the external frame (like the framing of a typical floor or ceiling), so those riser blocks were just added where I thought they made sense and seemed useful help bear the weight of the full frame. For the blocking, every other one was put in first with direct fasteners perpendicular through the joists. Then the opposing blocking pieces were added, and all of these were toe-nailed in place. I probably should have off-set them to make life easier though. I'm not a pro by any means and might have not done this all by the book. But it's holding up nicely 2 years in : )

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MarianC21

1 year ago

Beautiful plans and execution. I plan to follow with similar style. I am adding different footers and don't need to worry about freezing in So. Cal. Not much rain either. I will add the grass cover to avoid weeds growing up through the slats. I will also add railings and gate to keep dogs off - we plan to put a small size spa on the deck, so the footing and stability is the key ingredients for this recipe to success. Thank you so much for the excellent tutorial. The best one I found with all my research for weeks!

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seamsterMarianC21

Reply 1 year ago

That means a lot; thank you so much for taking the time to comment. It's been a great addition to our home and we've really enjoyed it. Good luck on yours! : )

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HollyMann

2 years ago

This turned out so nice. :)

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Fabeulous

2 years ago

Great Work! looks fabulous.
P.S. Im curious: What are these big tanks/holes next to your deck?

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dcampbell13Fabeulous

Reply 2 years ago

To Fabeulous: To me it looks to be the emergency egress from his basement the black solid frame plastic is there for safety so no one falls in the window well.

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Fabeulousdcampbell13

Reply 2 years ago

Jep. seamster answered before(dont know why his comment is missing) and said that this is for his windows of his basement. We have these "Holes" here in germany to but they look different. So at first i thought it is some kind of entrance to a mysterious underground shelter. :D

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seamsterFabeulous

Reply 2 years ago

My comments disappeared for some reason!

I kind of wish our window wells were actually entrances to a secret underground shelter. That would be cool!

But nope, they're just windows to a messy basement full of LEGO toys ;)

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guidess

2 years ago

Ooooo! I love your edges so much I am going to rip off my sides to do them that way! They make it look so finished and classy.

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seamsterguidess

Reply 2 years ago

Thank you!

It's a little more time+cost, but I'm happy every time I look at it. No post-project regrets whatsoever :)

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JahFyahh

2 years ago

Looks great. How much did it cost if you dont mind me asking. Im looking to build a deck aswell so im trying the get a general idea of prices.

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seamsterJahFyahh

Reply 2 years ago

Thanks!

I added some info to the introduction regarding the cost. It's certainly not cheap, but you can save a lot by doing it yourself. Good luck :)

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shambuda2000JahFyahh

Reply 2 years ago

I built mine using pressure treated wood and the total cost came to approximately 650 USD. I also built mine in stages to stagger the cost and labor involved (as I built it alone). If you built it out of the synthetic lumber the author used, it would have been significantly more costly.

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mbellows

2 years ago

Thanks for the information! We are considering putting in deck like this and this helps us a lot!

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seamstermbellows

Reply 2 years ago

You're very welcome. Thanks for checking it out!

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chilihook

2 years ago

Your deck came out great! I very much like the border around the edge, gives it a very high-end, finished feel. I'm curious about he blocks you used for footings and how deep they are in the ground. Are you concerned at all with them coming out of level due to freezing or water run off? I'd very much like to do an addition like this to my existing deck, but I have always been put off by the thought of having to dig - at least three feet down - through the ledge (my gosh - the LEDGE I have) and pour footings (to prevent movement due to freezing) when planning something like this. Your method would make it so much easier!

Thanks and great work!

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seamsterchilihook

Reply 2 years ago

Thanks!

My blocks are buried only about 2 inches or so. I'm not terribly concerned with them coming out of level, as the ground the deck is on is very well settled and we don't actually see much rain where I live.

If further settling is a concern, you can make a deeper layer of paver base. The deeper you go, the more compacted the earth will be that you're starting on, and paver base doesn't really settle after being compacted. That's one option, or just use deep concrete anchors (non floating).