Prep: Leveling by build up. Use sand?

[nina_online]

Hello,

Planning to put up an Intex UltraFrame 14' x 42" (or 16' x 48" if we can make it fit) where trampoline is now. Probably take it down in winter and put trampoline back up until next summer.

The site is not level, I would guess by 8"-12".

Uphill side is closet to our back door, Downhill side toward back fence.

Don't want to dig because:
1. Uphill side is near tree roots
2. I dont think I'd like the look of a partially sunken pool/trampoline facing the house.
3. Lots of labor to hand dig.

Friend suggested using railroad ties (secured with stakes) or cinder blocks to build a 3-sided containment area and fill with sand until level. That would be cheap - could get the lawn guy to do it...?

I saw some posts against filling, but saw a post saying it was fine and even being off level didn't end up being a problem. (My friend's is off level and no structural problems)

Question:
Assuming this is okay, do I fill with sand? (Friend says Intex box says no sand but it worked for her.) I like the idea of sand at the top, but maybe some pea gravel at bottom?

Thanks for your thoughts.

Nina

View attachment 62459.

 

[duraleigh]

When you level with that much sand, it displays some "liquid" characteristics and you'll have a problem keeping it all under the pool in a heavy rain....it'll wash.

Pea gravel is a better choice. "Fines" is the best choice. It's mostly pea gravel but with some dust in there and will compact very nicely. The quarry near you may call it something else.

 

[nina_online]

When you level with that much sand, it displays some "liquid" characteristics and you'll have a problem keeping it all under the pool in a heavy rain....it'll wash.

Pea gravel is a better choice. "Fines" is the best choice. It's mostly pea gravel but with some dust in there and will compact very nicely. The quarry near you may call it something else.

Thanks so much for your response.

I called a recommended landscaping materials place, Marcelo's Sand and Loam.

They have the following pea gravel:

1. 3/8" river rock pea gravel
Most expensive
Round smooth rock
They get it from Austin Aggregates

2. 3/8" screenings fine-to-dust crushed limestone (really fine, finest)
Cheapest
Crushed rock with sharp edges
They get it from Austin White Lime

3. 3/8" F-rock washed limestone gravel
Crushed rock with sharp edges
They get it from Texas Crushed Stone (this is the only pea gravel they have)

4. Mix of sand & 3/8" river rock pea gravel mix

(by 6 yard, 12 yard, 18 yard dumptruck)

The guy at Marcelo's was worried the pea gravel would tear the bottom of the pool (asked me but I didn't know what it the material was); he liked the idea of sand better. He was particularly concerned about 2 and 3 because of sharp edges.

I've seen posts about foam but have no idea what that is or whether it is appropriate for my situation.

I tried to find info on what Intex recommends as a base, but no luck.

Any thoughts?

Thanks,
Nina

 

[nina_online]

More info:

I called a pool installer. (A guy at Lesley's Pool Supplies said making a sand box would never be strong enough for the 30,000lbs of water, so that made me nervous.)
He mostly excavates but said building a sandbox works. We talked about using staked railroad ties.

He fills with "Clay sand" by the bag from home depot. Then he puts 4x8 sheets of pink panther insulation board ($13.50), then the tarp on top of that then the pool. Says its comfortable to walk on and avoids
pool bottom getting punctured.

 

[duraleigh]

#2. 3/8 screenings is the ticket. "Fines" was all I could think of but "screenings" are the same thing.....it's pretty user friendly.

Foam board on that if you want to but the screenings compact into a smooth surface.

Staked RR ties would be perfect but I wouldn't go much higher than two tiers (about 16") and stagger the top tier inward about 2 inches.

 

[CJadamec]

I always start these replies with digging down to make the site level is by far the preferred and best practice method of installing a pool.

The sandbox path you seek is filled with potential for failure even when done correctly.

The best fill is you listed will be the 3/8" screenings. I would normally say you want quarry process, 1 1/4" minus, or road base. Those are all pretty much the same type of fill. All of it is broken rock of all sizes mixed with sand and stone dust. You want it to no organic material at all.

Once you get you fill you will need to put it down in multiple lifts, or layers, each lift needs to be compacted with a mechanical plate compactor. The fill also needs to be kept damp while being compacted so that it fully compacts.

There are a few shots of the process in my build photo link.

 

[jeffchap]

I won't deny that digging down is undoubtedly the best option, but when it's not practical, a sand box can work. Mine has been up for 6 years now with no problems whatsoever.

Dimension at the ground for Intex 16' Ultra frame pool.

 

[cfherrman]

I would avoid buying bags of sand or rock at home Depot, not only is it way expensive but I also wonder about the experience about a builder that wants to use bags of sand/rock.

I hate railroad ties, they rot and don't last, they will fit the bill though. There is concrete blocks often called dragons teeth or something else that are made from leftovers from concrete jobs. They are very tall around 2-4' high, but if you dug down and set these blocks they will be there forever. Call ready mix concrete companies if you want to pursue that.

 

[nina_online]

I always start these replies with digging down to make the site level is by far the preferred and best practice method of installing a pool.

The sandbox path you seek is filled with potential for failure even when done correctly.

The best fill is you listed will be the 3/8" screenings. I would normally say you want quarry process, 1 1/4" minus, or road base. Those are all pretty much the same type of fill. All of it is broken rock of all sizes mixed with sand and stone dust. You want it to no organic material at all.

Once you get you fill you will need to put it down in multiple lifts, or layers, each lift needs to be compacted with a mechanical plate compactor. The fill also needs to be kept damp while being compacted so that it fully compacts.

There are a few shots of the process in my build photo link.

Thank you for your post. I looked at the site again with my husband, and the tree roots would make digging out not work.

Is the mechanical plate compactor in your Buikd photos the red thing that looks a little like a lawn mower?

Neither my husband nor I want to do the labor of creating this "sandbox." We are too old and tired, and it is quite hot here. I was hoping this "pool installer" would work out, he was going to charge $300 plus materials (he sounded like a one-man shop and not the highest quality). But I had my doubts about him. It sounds like using clay sand is not the way to go, and he didn't mention compacting. I wonder what kind of person we could hire to do this, but not cost a fortune. I can try to find cheap labor and hope I can supervise him well enough, I guess. I probably can't afford a large professional pool company.

MORE IMPORTANTLY, I have now read in 3 places that the wall should be a distance from the pool equal to 1, 2 or 3 times the height of the fill. (I've read all 3 figures: 1, 2 or 3). Our fill at it's deepest will be 8-12" high. But we were going to build a 14' x 14' square (or a few inches more) sandbox because we don't have much space. That only leaves us 1 foot between the sandbox and the fence, just enough room to replace pickets. In other words, the sandbox would be snug around the nominally 14' pool.

Any thoughts?

I just wanted a cheap and easy pool to put up during the hot months (Summer highs are 100 - 108) for my kids and their friends. Now I feel like I have to hire an engineer. :-(

 

[CJadamec]

Yep that little red lawn mower looking thing is a plate compactor. That's about as small as they come and it weighs about 150lbs.

I don't know about the guy who quoted $300 but that price wouldn't have even paid for the fill I needed under my pool, let alone the timbers to retain the edge. Granted you are planning a much smaller pool you will still need a good amount of fill for the height you are planning on going.

To make a long story short you really should have 2-3 times the height of the wall between the pool edge and the edge of the wall. If you make the sand box tight to the pool with that much wall height you run a high risk of the wall failing. You could build the wall with "deadmen" buried in the fill under the pool. Granted none of that helps it be a cheap or easy build.

Hiring a builder to come in and dig down for you is probably the cheapest option.

 

[nina_online]

Yep that little red lawn mower looking thing is a plate compactor. That's about as small as they come and it weighs about 150lbs.

I don't know about the guy who quoted $300 but that price wouldn't have even paid for the fill I needed under my pool, let alone the timbers to retain the edge. Granted you are planning a much smaller pool you will still need a good amount of fill for the height you are planning on going.

To make a long story short you really should have 2-3 times the height of the wall between the pool edge and the edge of the wall. If you make the sand box tight to the pool with that much wall height you run a high risk of the wall failing. You could build the wall with "deadmen" buried in the fill under the pool. Granted none of that helps it be a cheap or easy build.

Hiring a builder to come in and dig down for you is probably the cheapest option.

Thank you for all your help. We can't dig down because there is a tree at the uphill side and roots extend toward downward side. (see pic)

When you say "You could build the wall with "deadmen" buried in the fill under the pool", do you mean that might solve the issue of building the sandbox tight to the pool? We may be able to eak out a foot all around to make the sand box 15 x 15 (and still use deadmen...?), but I doubt it.

I think the only thing I can do is have a builder come and look and see what can be done and give me a quote; I await to hear your answer about deadmen solving the tight sandbox issue, though.

Thanks so much.

P.S. The $300 was labor only to build 3-sided retaining walls and add clay sand fill, put foam board on top, then tarp. I would pay for the materials.

 

[nina_online]

Any thoughts on what material to use to build the retaining walls? I'd like it to add, not detract from the value of the house (and appearance). Cinder blocks and railroad ties were suggested for strength and ease of installing, but I don't find them attractive. (Railroad ties = splinters on kids feet?) I assume any stone-looking blocks would be quite expensive. Wood might be good, but not some that would wear unattractively. The picture below looks nice - will it continue to look nice? Is that just 4 x 4? Treated?

View attachment 62526

 

[CJadamec]

Here is a good quick break down of what it takes for a good retaining wall. https://www.familyhandyman.com/land...ow-to-build-retaining-walls-stronger/view-all

I used pressure treated 6x6 lumber. I walk on it all the time and never get splinters. You can stain the pressure treated wood to make it nicer colors. It should last many years and not suffer any major deterioration in appearance.

The premade retaining wall block is also an option which comes in many sizes shapes and colors. You can use a geotextile fabric attached to the block wall that will take the place of a traditional timber deadman. You need to get block that is designed to take that option tho.

The timbers in your photo appear to be 6x6. The wall in the photo below, to the right of the picture holding up the sunflowers is made 6x6 and has a 2x8 cap board to dress it up. It's 38" tall to the top of the cap. You can see the end of 2 deadmen in the wall they are the squares where the wood grain looks different one is right above the right corner of the deck.

The next photo is an example of a readily available wall block making a 36" tall wall.

 

[cfherrman]

Here is a excellent idea, but might be costly.

Pull up the fence, around 20' or so, on both sides, pour a footing leveled with the ground on the right side of your trampoline or so. Backfill with correct amounts of rock and sand. Finish off with foam and pool. Reinstall your fence on the new fence footing. Two birds, one stone.

 

[nina_online]

W

The premade retaining wall block is also an option which comes in many sizes shapes and colors. You can use a geotextile fabric attached to the block wall that will take the place of a traditional timber deadman. You need to get block that is designed to take that option.

....

The next photo is an example of a readily available wall block making a 36" tall wall.

You might not have wanted to name brands, but are you talking about Pavestone, which Home Depot has? I went and looked at them. Is there another brand or store I should look in to?

It occurred to me to call Pavestone and ask them if their retaining walls are load bearing enough to support the pool. I'll do that Monday.

Thanks,
Nina

- - - Updated - - -

Also, any thoughts about using cinder blocks with stakes. I guess that would be rebar?

I don't want to use concrete or cement. Just dry stacked.

 

[cfherrman]

There is quite a bit of info on the internet about dry stacking, I can tell you that you do not want to motor blocks, it sucks.

 

[CJadamec]

Not afraid of naming names just don't want to limit your options. The ones at home Depot are just fine as are Lowe's or any other retailer. The ones in my wall are from Lowe's for one simple reason. They are the only dry laid block I could get in stock at the store rated to stack 36" high. Every other block I could get that day was only rated for 24".

In looking for a wall block for your purpose get one that has a cast in interlocking design. So that when stacked on top of each other the top one can't slide off over the front of the bottom block.

I wouldn't recommend cinder blocks unless you want to fill the center holes with rebar and concrete.

 

[nina_online]

I always start these replies with digging down to make the site level is by far the preferred and best practice method of installing a pool.

The sandbox path you seek is filled with potential for failure even when done correctly.

The best fill is you listed will be the 3/8" screenings. I would normally say you want quarry process, 1 1/4" minus, or road base. Those are all pretty much the same type of fill. All of it is broken rock of all sizes mixed with sand and stone dust. You want it to no organic material at all.

Once you get you fill you will need to put it down in multiple lifts, or layers, each lift needs to be compacted with a mechanical plate compactor. The fill also needs to be kept damp while being compacted so that it fully compacts.

There are a few shots of the process in my build photo link.

I called Pavestone and finally got to a general manager who consulted with an engineer.

The engineer says there should be a clearance between the inside of the retaining wall and the edge of the pool of 1.5 times the wall height (would come to 12-18"), and that the product should be
Pavestone Retani R16 (formerly Highland)
RETANI® RockFace D R612 |
18" W x 6" H x 12" D

My space can't accommodate the desired clearance plus a 12" deep wall.

So he recommended the following:

Create a "stabilized base" aka "cement-treated base":
1. Use "Flexbase" which is crushed limestone base with fines to dust. Sounds similar to the 3/8" screenings discussed in this thread. There should be a bit of moisture in it. e.g., if you try to make a "snowball", it will hold.
2. Build up from the downhill side in 4" lifts (layers), then use a plate compactor on each lift. When walked on, footprints should not show.
3. At edges, create a 1:1 (45%) slope.
4. Create a top layer of cement by spreading powdered cement on top of the final compaction. Lightly mist it down (with garden hose nozzle on fine spray). This creates a moisture barrier so the water would run off of it.

Any comments regarding this as the base for the pool? I could/should put the foam sheets in between the cement top layer and the pool bottom?

Thanks,
Nina

 

[CJadamec]

When faced with a procedure from a soil engineer I can't say as though I have any comments or additions to what they suggested. That sounds pretty well laid out. Lots of work.

A lot of people love foam under their pools. Its there to protect the liner from the ground and to make the bottom of the pool softer to your feet.

 

[nina_online]

When faced with a procedure from a soil engineer I can't say as though I have any comments or additions to what they suggested. That sounds pretty well laid out. Lots of work.

A lot of people love foam under their pools. Its there to protect the liner from the ground and to make the bottom of the pool softer to your feet.

Thanks. I didn't mean a critique of the engineering but whether a cement topped platform is okay for the pool liner. Sorry I wasn't clear.

I like the idea of the foam, though I don't actually know what the product is. Can someone post a link (e.g. from HomeDepot.com) to the foam? The "pool guy" said "4x8 sheets of pink panther insulation board." Would like to know exactly what that is and if it can be easily cut to fit (and how).

Thanks again to CJadamec and everyone else for your advice,
Nina