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 las...

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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49 Discussions

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!

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

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

1 reply

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.


2 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!

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

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
2 replies

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!

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.

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

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!!!

2 replies

It was built during the time I built the house. No Idea of construction time, but lots of design time and research on concrete tanks.

I planned the construction after reading about the " Besser Block " pool walls made from blocks made in Australia. Rather than ship blocks to Mexico, we used local lintel blocks and cut out sections of them for the floor / wall intersection. I have used surface bonding cement before and been very impressed.

It was planned out to the max - many pages of ideas and notes, and research on reinforcing/building concrete water tanks. That is all it really is- an easy to form, strong, watertight tank.

did u use gravel for your retaining wall? or just cement and sand?

2 replies

used my standard concrete mix - 1part cement, 1 part sand, 3 parts gravel.

It was concrete- cement, sand, and gravel + rebar.
Sand and cement mixes are not strong and get lots of shrinkage cracks.

Well done, I love the view on the end shot. Amazing.