DIY Concrete Swimming Pool




Introduction: DIY Concrete Swimming Pool

About: DIY is a way of life for me, building a geodesic dome house, a swimming pool, solar water and house heaters, passive solar house (in Nebraska), and recently a concrete house and pool in Mexico, For the last …

Building your own pool is not for everyone, but it can be done, with great results. When I got bids around $30,000 , the choice was to build it myself, or forget it.

For around $7000, and a lot of work, my son and I built a very solid 13' x 22' x5' oval concrete pool off our deck.

We built it on flat ground , but it could also be built in a hole and backfilled.

Keeping the plumbing simple also cut costs.

Block pools can have problems because they lacks the steel needed.

We used lintel block (normally used over doors and windows) to wrap rebar around the pool every 8 inches horizontally.

Stacking the blocks with cores lined up put a rebar vertically every 8 inches.

We cut the sides out of the base row of block to let rebar and concrete connect the wall and pool floor.

The result was a pool that could stay solid on the 3 ft. of rock backfill behind our retaining wall.

We plastered and waterproofed the pool ourselves with white surface bonding cement, and 2 years later hired a pro crew to do a finish coat of prettier blue cement plaster.

Step 1: Design

This pool had to be very strong, because it sits on backfill in an earthquake area next to the Sea of Cortez. The backfill was all rock, not dirt, which settles.

Block pools can have problems because they lack horizontal steel and they can leak where walls meet the floor.

Curved walls are much stronger than straight, so I chose an oval. I wanted #4 rebar every 8" vertical and horizontal in the walls and continuous through the floor. This is impossible with standard block, but lintel block has notches which let you add horizontal bars every 8"

We kept the pool 30" away from the retaining wall to allow access for plumbing and pump.

To use a small spa 1/2 hp pump we kept the 2"return and 1.25"supply lines large and close to the pump.

A cartridge filter completed the plumbing.

Waterproofing comes from the cement plaster inside a pool. Any crack in the structure means a leak, as the crack will continue through the plaster.

We used fiberglass reinforced plaster inside and out to hold the blocks solid until the concrete was poured cured. This alone waterproofed the pool.

Step 2: Structural Steel Reinforcing

Once the ground was flat, we poured a shallow footing for the block. This was to stabilize the walls until the floor/wall cores were poured. The pool weight load is spread evenly on the pool floor when filled with water so the strength this footing is not important later.

One row of block was set in mortar below the pool floor as a level base for the rest.

We ground all the block flat top and bottom. Then we glued (construction adhesive) one row of lintel block with inside cut out level with the soon to be 6" thick floor. A bent rebar is fed through every core, overlapping the 1' on center rebars in the floor. Every horizontal row of block gets a rebar in the notch of the lintel blocks, making a continuous rebar circle every 8 inches. The result was a pool that would stay solid on the 3 ft. of rock backfill with no wall/floor crack. The floor and wall cores are poured at one time.

Step 3: Wall Stack and Plaster

We drilled holes in the blocks for all the return and pressure pvc pipes, and cemented them in with expansive cement. Fittings are available to point the water flow in the direction you want it to circulate.

A floor drain tube ( 2" in our case ) gets positioned at the low point of the pool. Your temporary screeds should all go downhill to this drain so crud gets pulled to the pump/filter.

Installed the pvc return weir with expansive cement following their instructions. Normal cement shrinks, and leaves a crack.

Blocks are stacked with no overlap so cores match up. Any rebar is overlapped a foot and tied with wire. Blocks are stacked to the waterline. The inside and out of the block is plastered with 1/16" minimum thickness surface bonding cement to hold the block while concrete is poured. A rubber float makes spreading this easy. It dries quickly, so mix just a little at a time, and clean tools every 10 minutes, or kiss them good by.

Surface bonding cement (it has latex glue and glass fibers in it ) holds blocks better than mortar, and also waterproofs the wall. Our pool was was waterproof with a second coat on floor and wall after the pour.

A solid 12"concrete bond beam gets formed with 14" plywood. We wanted a vanishing edge so that part is formed an inch below the final water line to leave room for tile. This edge needs to be angled (we did down on the outside ) so water will not sit on the tile. We built a large catch basin below the edge, but I won't get into that. It is not easy to design the size of the basin.

Now you are ready to pour wall and floor.

Step 4: The Pour (get a Pumper)

We pumped ready mix over the house and first on the floor, then into the cores and bond beam in a continuous pour. Without the pump, you need a dozen strong men to hoist the concrete up in buckets- It is a lot of concrete, and you have to do it without stopping. The concrete cannot be runny, so you need a spud vibrator to consolidate the concrete in the cores and into the floor pour. You can rent these, or buy one for $100 at harbor freight.

The concrete should be 6.5 sacks/cubic yard and have both fibers and a water reducing superplasticizer admix. The pumper will want to add water for easy pumping, but you should add more water reducer instead of water. Too much water and you will get shrinkage cracks.

Remove any rocks or bricks holding up the rebar. The rebar must be in the middle of the 6" floor. Too high or low and it will rust and break the concrete.

Leave the surface rough, as in broom or wood float finish. The plaster bonds much better to rough concrete.

Cure the concrete for a full week. The floor is easy- flood it the next morning. Leave the bond beam forms on for a week and keep the top moist. The plaster on the walls keep them moist.

Step 5: Plumbing

It can be as simple as hooking up an above ground pool pump and filter with hoses over the edge.

We did ours with conventional pvc and a 20 year old 3/4 hp spa filter pump, later replaced with the same size, but two speed. You don't need a big pump. It just uses more electricity.

Step 6: Steps

If you do steps add them after the pour and the area below them is waterproof. They can take a lot of concrete. Next time I would go for narrow steps and more pool space. We poured a layer ( step) at a time and ended up adding lots of rocks and bricks as filler inside the concrete.

Step 7: Deck

Since our pool was free standing, we added a deck on two sides, all conventional concrete that overlapped the pool edge, leaving us with nice spot to enjoy the sunsets of San Carlos, Sonora, Mexico.

Approximate Costs

Lintel Block $600

Concrete 21 yards @$140/yd $ 2940

Steel $440

Plaster $160 (We made our own)

Glue $70

Pump $240

Filter $180

PVC plumbing $280

Total- about $5000

+ heFinal plaster and edge tile $2400 (two years later by pool plaster contractor- It is much prettier and smoother than my plastering )

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Participated in the
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1 Person Made This Project!


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6 years ago

Hooray! I've been trying to convince my husband to let me dig a pool into our hill (not nearly as steep as yours), and your gorgeous success and ambition gives me the science behind my daydream! Thank you so much. I know its a lot of elbow grease and heavy lifting, but now I know it can be done!


Awesome pool! With a view like that, I might have added a window to it!


Reply 6 years ago

I considered the window, actually a salt water see thru aquarium section of wall, but reality set in and I cleverly ignored the idea.


7 years ago on Step 7

This is the coolest project I've seen on Instructables. Great info on the concrete work. Thanks for sharing.


Reply 6 years ago

Thanks! I will put that compliment on the refrigerator.

Once I realized I could use lintel block so the rebar would encircle the pool, every thing else fell in place.


6 years ago

I built my in ground pool with my son around 8 years ago. It is very similar to yours and I made a couple of mistakes. I made it too deep, only 1.2 mts high water level would have been better for keeping warm, kids playing and well swimming is the same. I added a 2" water solar heater on my roof, used cheap irrigation pipes and they pump to the roof during the day every 30 minutes for 5 minutes draining back into the pool via the filter etc. Your place looks great. I live in Costa Rica and we have had plenty of 6+ earthquakes and no cracks. Sadly the kids get bored with it and it is used just a handful of times a year. I always dreamed I would have a pool in my house and it was only possible by doing it myself. Your home is better with that pool. I added a roof over mine to stop leaves falling in from nearby trees and sunburn. The roof has skylights and cheap drain pipes in a spiral to heat up the pool. At sunset it is the perfect end to the day with a cold beer. Don't listen to folk saying no, they often never do anything let alone such a challenge. WELL DONE!


7 years ago on Step 7

Thanks for sharing this wonderful project! An inspiration. :)


3 months ago

Thanks for all your nice compliments. Seven years later and no problems except keeping it clean from the leaves that blow in.
But consider how to cover a pool if you heat it in the winter, and shade it in the summer in a climate like San Carlos, if you are building one.


Question 3 years ago on Step 1

I want to build a concrete swimming pool, but you know the concrete is porus, I am afraid the water will penetrate through floor and wall, do you think if we build a concrete inground swimming pool, what kind of material or membrane can be used under the concrete, or the material can mix within the concrete?


Answer 3 months ago

Concrete is porous. The waterproofing is the high cement surface coating applied after the concrete is cured. Pool contractors usually apply a special cement coating for pools that has color and special sand filler;


3 years ago

How was the coving (rounded corners between side and bottom) done?


Reply 1 year ago

The day after the walls and floor was poured, we added the bottom coving, using acrylic glue and regular concrete.


1 year ago

I cannot get instructables to allow me to return more comments- too old I l guess.
Here is the DIY surface bonding formula from the USDA I used to plaster the pool. There are commercial products available to these specs, but I can't find them locally.

Commercial Surface Bonding Premixes
Dry, premixed surface bonding is now being packaged by a number of firms and is available on the retail market. Building material dealers, concrete products plants, and paint stores will be stocking these products as they become more widely used. The bag sizes range from 25 to 80 pounds. Some premixes require only the addition of water. Others have a small plastic envelope filled with calcium chloride inside the bag. The calcium chloride should be mixed with water before making the wet mix. Some premixes contain sand and should be applied one-eighth inch thick. Those without sand need be applied only one-sixteenth inch thick. Follow the manufacturer’s directions on the package.
The price of commercial premixes may run as much as three times the cost of ingredients
for home mixing. However, the commercial products are accurately proportioned and eliminate most of the labor of mixing. They also eliminate the need to locate ingredients, some of which are sold only in large quantities.
Inspect the premix before using it to be sure that the fibers are well distributed; if they are not, remix. Also, inspect for frayed glass strands. If there is a large amount of frayed strands in several of the packages, do not accept the commercial premix. It will be difficult to mix and apply. Try to get packages from a different batch, as manufacturers are experimenting to get proper control in mixing their product.
Remix as little as possible. Too much mixing frays the strands or separates the strands into individual filaments. This makes proper application of the bonding mix diffi- cult.

Ingredients for Home-Mixed Surface Bonding
Ingredient Parts
Cement ...,......... ‘78 Lime ............... 15 Calcium stearate . . . . . . 1 Glass Fiber .......... 4 Calcium chloride ...... 2
Total ........... 100
19l/2 3314 114
25The ingredients for home-mixed surface bonding are as follows:
l Portland cement (normally packaged in 94-pound sacks). White cement is more expen- sive than regular gray cement but is less alkaline, has a more finished appearance, and needs less mineral coloring for pastel shades if you desire to color the mix. It is preferred for
all uses, but regular type- I gray cem-ebb% sometimes used.
l Hydrated lime (normally packaged in 50-pound sacks). Hydrated lime makes the mixture more workable and easier to apply. Lime with lowest alkaline content is made from pure dolomitic limestone.
l Calcium chloride (normally packaged in lOO-pound sacks), in flake or crystal form. Calcium chloride makes the mixture set up quicker and results in a harder surface. It is available from agricultural chemical dealers and from distri@tors handling it for ice and snow removal.
l Calcium stearate (normally packaged in 50-pound boxes). Calcium stearate makes the mix waterproof. Use a wettable technical grade, generally available from chemical distri- butors.
l Glass fiber filament chopped into one half-inch lengths (normally packaged in 40- or 50-pound boxes). Type E fiber, coated with silane or chrome organic binder, is available from plastic and chemical supply distributors. An alkali-resistant fiber, type K, may be available from building material dealers and plastic products dealers. The glass fiber acts as reinforcement in the mixture to give it strength and prevent cracking.
Home Mixing the Materials
The bonding mix sets rapidly after the water and calcium chloride have been added to the dry ingredients, especially in hot weather. If one person is plastering, prepare only 25 pounds of bonding mix at one time.
The weights of the ingredients needed to make a 25-pound batch (dry weight) of the bonding mix are as follow,s:
Mix-in dry form-the cement, lime, and calcium stearate thoroughly. Add the glass fiber and remix only long enough to distribute the fibers well. Too much stirring tends to break up the strands into individual filaments. When this happens, the bonding mix is hard to apply.
If mortar or concrete coloring is to be used, blend it into the dry mixture of cement, lime, and calcium stearate before the fibers are added. Dark colors are not recommended because they tend to splotch and fade. Even with light colors, weigh each batch carefully to avoid differences in color tone from batch to batch.
Mix the calcium chloride with 1 gallon of water. Add this solution slowly to the dry ingredients and mix thoroughly. Add about one-half gallon more of water. You may need to adjust this amount of water slightly to
produce the right consistency for good trowel- ing. The mix should have a creamy consis- tencyas thin as possible but not too thin to prevent handling with a trowel. Most people tend to make it too stiff. It will then be hard to apply and may not bond properly.
Mixing can be done by hand in a wheel- barrow or small mortar box. A garden culti- vator rake or weeding hoe (three- or four-tine) works best. Check the mix with your hands for lumps. Wear rubber gloves to avoid possible burning of the skin.
A power-driven plasterer’s mixer can be used (fig. 22). Put the water-calcium chloride solution in the mixer first and add the dry mix slowly .
If the mix becomes too stiff before it can be completely used, add a small amount of water. Do not add water more than 30 minutes after 15

Figure 22.-Motor-driven plasterer’s mixer for mixing small batches of surface bonding. The cylindrical metal container rotates against a rubber or plastic blade, creating a scraping action that does not cause the fibers to “ball up” as with other types of mixers.
the initial mixing because it weakens the bond. Discard such remixed batches whenever the material again becomes too stiff to apply on a wet wall.
Batches of the dry ingredients can be mixed well in advance so that there will be no delay in preparing the mix when it is time to begin the bonding operation. If the dry mix is to be stored several weeks, place each batch in a plastic or multiwall paper bag and close the top tightly. Weigh out the calcium chloride for each batch and seal it in a separate plastic bag; do not mix it with the dry ingredients.
Applying the Bonding Mix
Surface-bond both sides of the wall. It will not be strong enough if the bonding mix is applied on only one side.
The blocks must be free of dirt, loose sand, cement, and paint. If necessary, clean the blocks with a wire brush when they are dry.
Spray the wall with water until it is wet but not dripping.
Work the mix from a hawk onto the wall
with a plasterer’s trowel (fig. 23). Hold the hawk against the wall to avoid excessive spilling of the mix.
A very thin coatabout one-sixteenth inch thick-of the bonding mix is all that is neces-
Work from the top of the wall downward.
Thus, if the uncoated portion of the wall needs rewetting, the water will not run over freshly applied bonding.
Most workers can cover a section about 5 feet wide standing in one position. Start applying the bonding 2 or 3 feet from the top of the wall and trowel the mix upward to the plate. Move down another 2 or 3 feet and repeat the process, blending the freshly covered section into the bottom of the section above.
There are four essential steps in successfully applying and finishing the bonding:
1. Apply the mix with firm trowel pressure, pushing the load upward and outward until a fairly uniform coverage is attained.
2. Follow with longer, lighter strokes, hold- ing the face of the trowel at a very slight angle to the surface (about 5”) to even up Figure 23.-Work the bonding mix from a hawk onto the wall with a plasterer’s trowel. Note the specially made hawk with turned-up edges on three sides to prevent spilling the relatively thin mix.

the plastered area and to spread excess
bonding mix to fringe areas.
3. Move to the area below and apply mix as
in steps 1 and 2. Continue bonding for 15 to 20 minutes, or until you have covered 25 to 30 square feet of surface.
4. Dip the trowel in water to clean it. Retrowel the first area, holding the trowel at a slight angle as in step 2. With firm pressure and long strokes, sweep over the area only enough to smooth out any unevenness.
T OO much retroweling may cause hairline cracks, or crazing. In addition, a slightly fibrous texture has a more pleasing appearance and hides unevenness in the surface better than does a very smooth surface.
A calcamine brush may be used to obtain a pleasing, brush surface in place of the troweling described in step 4. Brushing must be done with light strokes immediately following step 3, before the mix begins to set. In hot, dry weather brushing may need to be done on smaller areas immediately after step 2. Use either horizontal or vertical strokes depending on the surface effect desired. When the brush begins to drag because of mix collecting in the bristles, dip the brush in water and shake out the excess. This will probably have to be done after brushing an area of 10 or 15 square feet.
A stippled surface may be obtained with a paint roller from which the fibers have been burned off with a torch. The fibers melt, leaving nubs on the roller surface. Follow the same procedure as described for obtaining a brushed surface.
If the bonding application must be stopped for 30 to 45 minutes or more, try to stop at a corner or at the edge of a window or door opening, particularly when color has been added to the mix. Color differences that might occur between batches will then be less appa- rent.
Fill in the corner junction between the wall and footing, carrying the bonding mix onto the top of the footing on both sides of the wall (as illustrated in fig. 20). If the wall is built on a concrete slab floor on grade, carry the surface bonding down over the outside edge of the slab to help seal the joint between wall and floor (previously indicated in fig. 5).
Wet the finished bonding with a fine spray of water once or twice the first day to aid curing.
Roof construction can begin 24 hours after the bonding is completed, but a longer waiting period is desirable. Erecting the roof before applying the surface bonding is advisable because interior work can be done during inclement weather. Also, the added weight of the roof helps to seat blocks in the wall firmly.
Coverage of the Bonding Mix
Twenty-five pounds (dry weight) of bond- ing mix should cover at least 60 square feet of wall, or about 30 square feet of wall bonded on both sides.
Time Requirements
The time required to erect and complete surface-bonded walls will depend on such factors as the levelness of the floor or founda- tion on which the walls are to be erected, the building experience and skill of the workers, the quality of the concrete blocks (particularly uniformity of dimensions), and the building design-specifically, the number of window and door openings and offsets in the walls which involve interior corners. However, a conserva- tive average would be 5.0 man-hours per 100 blocks for stacking and 2.5 man-hours per 100 blocks for surface bonding.
Sanded Bonding Mix
If a sanded surface is desired, add 1 part of sand by weight to 1 part of regular bonding mix (dry weight). This must be applied one- eighth inch thick to give adequate strength and waterproofing. The cost will be slightly higher than the unsanded formulation previously des- cribed. Use a clean white sand such as that sold for playpens; about 100 percent should pass a No. 10 screen and 75 percent should pass a No. 20 screen. The same amount of water is needed for 50 pounds of sanded mix as for 25 pounds of unsanded mix. 17


6 years ago

Very nice pool!

I built my own concrete pool, but it's hot tub sized, much smaller. I found your article while looking for pool coatings. I originally used Drylock waterproofing paint, which worked initially, but developed cracks at the seems between the blocks. I re-painted numerous times. Then the paint began to break off in large chips. Now I am removing all that old paint with a masonry hammer and an angle grinder. Lots of hard work. Once I remove all the paint down to the bare concrete, I plan on re-coating it with something and I am looking for the right product.

Could you explain the "plaster" that you used?



Pics show condition now and whole pool several years ago.

20160718_185410_Belvidere Avenue.jpgPool-045.JPG

Reply 4 years ago

Hi DonaldD44-- I was wondering what you ended up using for the re-coating of your pool? I have a very similar pool that needs re-plastering. I don't need the full tutorial, as the pool is already made and just needs to be re-plastered-- what type of plaster/cemet mix did you end up using and how did it turn out? Thanks!


Reply 6 years ago

Standard "surface bonding cement" will work. Remember that surface prep is the most important. Paint a latex glue on that is 100% acrylic based and surface bond while it is wet.
For a small pool I would consider buying the premix pool plaster from a pool building company. To that I would add alkali resistant glass fibers from a ready mix company (maybe home depot) so that the mortar joints of the blocks are bridged with the fibers.
You can mix your own from my formula (in the comments), but it requires a number of materials you might find hard to get in small quantities.


5 years ago

Absolutely beautiful! Too bad can't find a man with as much motivation as you! Your other half must be proud!


6 years ago

This is really amazing. So innovative and functional and it looks really incredible. I was curious how long it took you to plan and how long the actual construction took. Did you draft your design/plans out first? And if so, did you have to make adjustments on the way? I really can't overstate how amazed I am at this. Well done!!!