Above ground pools for dummies (part II): Site preparation

This post is part of the six-part series dedicated to above ground pools:

• Part I: Introduction
• Part II: Site preparation (this post)
• Part III: Pool assembly
• Part IV: Pump/filter/skimmer
• Part V: Chemicals
• Part VI: Conclusion
• Part VII: Post scriptum
• Part VIII: Post post scriptum

Site preparation is a critical step which, if not done right, could lead to a (pool) disaster. Depending on your site, it can be done quicky for little money or it may take weeks and cost more than the pool itself. I'm not an expert, so let me just share the things I learned when I did research and explain what I did (and why) step by step. Keep in mind that my pool is INTEX 26355EH Ultra XTR Deluxe Rectangular Above Ground Swimming Pool Set: 18ft x 9ft x 52in [sponsored link].

LEVELING

The most critical part of the site preparation is to make sure the ground is leveled (and, depending on the model, the pool base may be a couple of feet wider than the pool dimensions). My original backyard had a slight slope (I estimated something around 10-15 degrees), so during the ADU construction, I asked my contractor to level the backyard. I'm really glad I did because I would not have been able to do it by hand (the soil was so hard that the crew had to switch from a small bobcat to a bigger excavator to finish the job).

When leveling the site, go by the lowest point (think digging instead of backfilling). If you backfill the lower sides with whatever material you pick (sand, soil, etc.), chances are after some use, it will compact and the pool base will get unleveled again (under the pool water pressure, after rains, etc.). You do not want it to happen when your pool is full.

TAMPING

Although, my backyard was more or less leveled, it was still not pool-ready: some parts were not even and the surface was covered with a couple of inches of decomposed granite which is not the best material for a pool base. The basic challenges I had to address were making the area perfectly leveled and smooth.

First, I had to loosen the compacted decomposed granite. The surface was tough, but once I started breaking it with the shovel, the decomposed granite layer loosened up. I followed with a rake and moved decomposed granite around to level any visible gaps at which point it was ready for tamping.

There are different ways of leveling and tamping loose surfaces like sand and decomposed granite. I picked the easy and often recommended approach that relies on a level attached to a 2"x4"x10' piece of lumber (you can find the video instructions here, here, or here, just keep in mind that despite what some may recommend, you should not be using more than a sprinkle of sand unless you build a base around it, like this guy did). I did not have any extra decomposed granite for filling in the small gaps, so I added a few bags of sand. Finally, I watered the area and used a hand tamper tool [sponsored link] to compact the surface a bit.

SMOOTHING

Because my pool base was still covered with decomposed granite, I was afraid that the sharp edges of the small stones would cause damage to the pool liner. Although, some experts claim that the pool liner should tolerate the small sharp objects, I did not want to take the risk. I also wanted the bottom to feel good under the feet. First, I planned to use sand, but after doing some research, asking Intex and getting a reply advising against it, sand was a no-go. Then I wanted to buy a pool liner guard such as Rhino pad or Gorilla pad [sponsored links], but the reviews I read were mostly disappointing (people were mostly complaining about them being not much better than the weed fabric), so I decided against it. Another option I considered was the interlocking foam mats, but they would be a bit more expensive (at least, the thicker ones) and seemed inferior to the option which I finally chose. And what did I choose?

I chose Insulfoam R-2.89, 1-in x 4-ft x 8-ft Faced Polystyrene, AKA foam boards. I read several reviews from people praising them and the only negative I found was a comment from one expert suggesting that they may cause rust in traditional (hard-sided) above ground pools. Since this potential issue did not apply to my soft-sided pool, the foam boards seemed like the best solution.

Foam boards come in different thickness, but the thicker ones are significantly more expensive and the thinner boards are not sufficiently cheaper to justify the downgrade, so I went with the one-inch thick boards. To cover the pool base, I needed (if I remember it correctly now) seven 1"x4'x8' boards, which cost me a bit over $100 (I was able to get a discount on several boards which were chipped a little but totally functional for my use). Lowe's website showed thew boards I bought as unavailable at the time, but I could find them at several local stores (and I suspect the similar foam boards from a different maker would work as well).

To join the boards together, I used silver Gorilla Tough & Wide Duct Tape, 2.88" x 25yd [sponsored link]. 25 yards were just enough.

I will cover additional materials I used under the pool base later, but at that point, the important part to remember was that the pool would be installed on top of the one-inch thick foam boards. Some people said that the boards would compact a bit under the weight of the water. I cannot validate if this is the case, but I assumed that it would be unlikely due to uniform weight distribution. I may be wrong and I will check when I have to disassemble the pool at some point (hopefully, not very soon), but for now, let's assume that it's not the case and stick with the one-inch number. Why is this number important? Because, that's how high the leg support should be above the ground to stay on the same level as the pool base. Which brings us to the leg support.

LEG SUPPORT

My pool came with 12 U-shaped legs, two on each short side, and four on each long side. For the leg support, unless the pool is installed on the hard surface like concrete or pavement, Intex recommends using pressure treated lumber. I checked the local Lowe's and Home Depot stores, but did not find the lumber I liked. Everything I saw looked like it would not last a couple of seasons. I thought about using bricks, concrete blocks, but ended up buying 12"x4"x8" Concrete Retaining Wall Block at under $3 a piece.

I used two blocks per leg, so needed a total of 24 pieces. The area covered by two blocks is four inches short (in length) of what Intex recommends (Intex recommends 16"x16" when the two blocks cover 16"x12"), but they worked fine for me. I would definitely recommend using these instead of the thinner concrete blocks available at home improvement stores because I saw many complaints from people about the thinner concrete blocks breaking under pressure and causing all kinds of issues (in extreme cases, pools had to be replaced). I'm sure these guys will outlive my pool.

Now came the challenges. First, I had to burry the blocks in the ground, leaving about one inch exposed, so that the top of the blocks would be on the same level as the top of the one-inch thick foam boards. The trick here was placing the blocks at the exact locations where the legs would be. The Intex pool assembly instructions assume that you install the leg support while you are building the pool, which is weird because regardless of what material you use, the leg support would need to be dug into the ground and leveled first. Even with the pool parts spread on the ground it is not quite clear where exactly the bottoms of the pool legs will end up, so I'm not sure why Intex does not include the map of the leg support location.

Fortunately, I found a third-party map for my pool model which was almost accurate (I don't know if the dimensions changed, but the more accurate map would bring the centers of the support pads about two inches closer to the center of the pool on each side, as I explained in the post comment).

The second challenge was leveling the blocks. To make them easier to level, I dug the ground a bit deeper and wider. I put a bit of sand in each hole and used my home-made level tool (the 2"x4"x10' with the level attached) to measure the heights. I used a regular level for aligning each block pair and a self-leveling laser level [sponsored link] to make sure all blocks are leveled against the each other.

Leveling the leg support blocks was the most difficult job of all. Not only because the blocks are heavy, but the leveling tools I used (both the home-made and the laser one I bought) were not perfect. For my home-made tool, I picked the straightest piece of lumber I was able to find, but I still could not guarantee 100% straightness.

The laser level had its own limitations: I could not see the laser beam (including the green beam which is supposed to go further than the red one) on a bright sunny day, so I had to do it in the evenings. Also the target piece that came with the laser level was a PITA to align. But as any torture, the leg support leveling job came to an end it looks like I did a good job: everything except one corner which is about 1/2"-1" lower than the rest seems leveled (I messed up the corner because I did not realize that the liner would reach that far, not a big problem for now).

PADDING

After installing the leg support blocks I was ready to finalize the pool base pad. Here is what I did.

1. Installed two layers of weed fabric.

2. Put the ground cover that came with the pool on top of the weed fabric:

3. Installed the foam boards (used Gorilla tape to attach them together):

4. Covered the foam boards with the 10'x20' 20-mil tarp:

At this point, my site was ready for the pool installation, which I will cover (including the mishaps I ran into) in the next post.

P.S. There is one site preparation step that I skipped, but you may want to consider: applying herbicide. From what I learned, the main floral threat to an above ground pool comes from different variations of nutgrass (or nutsedge). This bastard can grow through pretty much anything and it is extremely hard to kill. Most herbicides do nothing for nutgrass and among the ones that do, some cannot be sold in or shipped to California. I tried Empero Q-Pak Nutsedge Killer [sponsored link] on some nutgrass looking weeds around the house and it did work on some, but not all. It also required at least a couple of applications. The instructions say that you need to apply it to the leaves, but I did not see any nutgrass in the area of the pool base, so I thought that applying the herbicide to the ground would be a waste. If you are about to install a pool in a new area, I'd recommend nutgrass treatment before you start digging the ground.

SEE ALSO

• How to level above ground pool - Further Reading
• What to Use for Leveling an Above Ground Pool
• What Should You Put Under Above Ground Pool Legs?

NEXT: ABOVE GROUND POOLS FOR DUMMIES (PART III): POOL ASSEMBLY

PREVIOUS: ABOVE GROUND POOLS FOR DUMMIES (PART I): INTRODUCTION

FIRST: INTRODUCTION