Above Ground Pool - Ground preparation and other questions

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David

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Apr 14, 2009
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Hello Everyone ;-)

I am a first time pool owner; we had a pool when I was kid for many years - and now that I have children of my own, I figured they should have one too. I picked up a used pool last fall; it was in excellent shape - the previous owner even kept all of the manuals. It is a 21' round Cornelius pool. I've decided to go with the partially in ground above ground pool route... with somewhat of a twist. Last fall, I dug the hole for the pool. The ground was greatly disturbed... to give some context to this statement, I borrowed mini-Excavator, and when all was said and down - I hauled 42 yards of dirt out of my backyard. I tamped the ground down firm, and let the hole sit over the winter. Thus far, it's been an interesting Michigan spring -- rather wet, and much to my dismay - the ground is rather mushy. It's a nice mix of clay and sand. The hole is about 23-24 feet around, and I've created a psuedo retaining wall. I acquired a large number of industrial roof decking (B-Deck to be specific - http://www.metaldeck.com/b_deck.htm) and using 5 foot lengths of 1-1/2" angle iron - I've screwed all of the decking together, driven the angle iron into the ground, and screwed the decking to the angle iron.

So, yeah.

My next step is I want to level and create a firm surface to set the pool on -- I'm just not quite sure what to do. Mother nature has definately assisted in the ground compaction process over the winter, but I need to fill my "pit" with a sand of sorts, level it - and then start the pool assembly. The end goal is after the pool is setup within my ring, to backfill the space between the ring and the pool wall with pee gravel, and then backfill any remaining gap between the ring and the outside ground with dirt, then use landscaping pavers to create a nice border around it. On the high side of the yard, I've gone down 3 feet - and 2 feet on the lower end of the yard. I'm tempted to use a slag sand -- and create a nice firm hard level base, and then use foam for the pool bottom... but I like the idea of scooping out the middle of the pool as well, and I don't think foam is going to lend itself to that very well.

Any suggestions would be appreciated -- I know that I need to get it level (and it's reasonably level now, but needs tweaking) -- and a solid surface to set the posts on. Just looking for a little feedback on my already overengineered project ;-)

Thanks in advance,
David
 
I'm no expert, but growing up in southeastern Wisconsin gives one a lot of experience with clay. In the presence of water the clay just doesn't want to firm up no matter how much you compact it, and the sand doesn't help. With that type of soil I'm guessing that the key is to be sure that the area drains properly either by grade management and/or drain tiles. At 1 lb per pint, the water in our above ground pools is a pretty heavy load. Even a 1 inch shift from level can cause problems for the wall on the loaded side. We built our pool into a slope (so we dug a horse-shoe bowl) but used retaining walls on the high side to maintain a 3 foot clearance rather than backfilling to the pool wall (I surrounded the pool with a deck so I didn't need to bury the walls). I laid drain tiles behind the retaining walls plus I graded the area around the pool so that the water flows out of the horseshoe and continues down the slope to the natural drain paths leading to a creek. Everything has stayed rock-solid over the winter and looks good so far through the wet spring.

Under the liner, we used that finely screened mason's sand on top of our soil, but I was told not to substitute sand for poor leveling (i.e., not more than an inch or so of sand). Then came the cove and the happy bottom. So far, so good, although we have a few low spots where the sand flowed into poorly compacted areas where the attachment pans for the 'L' bracing lies. Blame that on the PB and the rush they got in due to the epic floods in Iowa last year. However, our bottom is flat - I don't know if you need something that sets up better than sand for a bowl bottom or deep end.

Kelly
 
rather wet, and much to my dismay - the ground is rather mushy.
Click to expand...
Yeah, I'm with Kelly. Unless you provide proper drainage to let the water gravitate out of that clay (VERY slow process here in the Southeast), you'll probably never be able to get a stable bottom
 
David said:
Hello Everyone ;-)

I am a first time pool owner; we had a pool when I was kid for many years - and now that I have children of my own, I figured they should have one too. I picked up a used pool last fall; it was in excellent shape - the previous owner even kept all of the manuals. It is a 21' round Cornelius pool. I've decided to go with the partially in ground above ground pool route... with somewhat of a twist. Last fall, I dug the hole for the pool. The ground was greatly disturbed... to give some context to this statement, I borrowed mini-Excavator, and when all was said and down - I hauled 42 yards of dirt out of my backyard. I tamped the ground down firm, and let the hole sit over the winter. Thus far, it's been an interesting Michigan spring -- rather wet, and much to my dismay - the ground is rather mushy. It's a nice mix of clay and sand. The hole is about 23-24 feet around, and I've created a psuedo retaining wall. I acquired a large number of industrial roof decking (B-Deck to be specific - http://www.metaldeck.com/b_deck.htm) and using 5 foot lengths of 1-1/2" angle iron - I've screwed all of the decking together, driven the angle iron into the ground, and screwed the decking to the angle iron.

So, yeah.

My next step is I want to level and create a firm surface to set the pool on -- I'm just not quite sure what to do. Mother nature has definately assisted in the ground compaction process over the winter, but I need to fill my "pit" with a sand of sorts, level it - and then start the pool assembly. The end goal is after the pool is setup within my ring, to backfill the space between the ring and the pool wall with pee gravel, and then backfill any remaining gap between the ring and the outside ground with dirt, then use landscaping pavers to create a nice border around it. On the high side of the yard, I've gone down 3 feet - and 2 feet on the lower end of the yard. I'm tempted to use a slag sand -- and create a nice firm hard level base, and then use foam for the pool bottom... but I like the idea of scooping out the middle of the pool as well, and I don't think foam is going to lend itself to that very well.

Any suggestions would be appreciated -- I know that I need to get it level (and it's reasonably level now, but needs tweaking) -- and a solid surface to set the posts on. Just looking for a little feedback on my already overengineered project ;-)

Thanks in advance,
David
Click to expand...

two things...I didn't see anything here about using patio blocks under your uprights, but most pool builders use them under the uprights for added stability I think they used 24 on my pool build. The other thing is and this I suppose is a matter of preference...but the pool builder I used said not to use pea gravel...because it is so small and compact it does not allow for drainage into the earth...it holds water. I backfilled with dirt up to 4 inches and then put large river rock on top of that. It looks nice holds the back fill in place, and it doesn't hold water so the rain water goes under the liner. These are just suggestions, but my builder had 20 years of experience and he told me anyone who has used pea gravel has had water get up under the liner and cause problems like washout of the sand and that sort of thing.

Good luck and I look forward to pictures!!!
 
I would say that if you have to "add" anything to get that ground compact and solid, go with class 5. They use it for parking lots. We did not have the choice of digging down to solid ground to level out before putting our pool in - we are situated in a drained swamp so had to bring in 20 yards of class 5 and a plate compactor to build up before we could put the new pool in. We had pools for many years but when we went with the big oval, it had to be right. Clay is a disaster to build a pool on, anyone who has had to deal with it will tell you so. We are in a very severe winter area where we get frost heaving and have never had an issue - ever.

Also, you NEED to have the 1-2" pavers under your uprights. They are installed level with the ground. Use a transit to be sure you are level within 1/4-1/2" all the way around. Proper ground prep is 75% of the job. You can check this YT we made to see what we did, there are also others out there but this is a quick summary anyway.

[youtube:1c6iany7]XAZvDSFUoVo[/youtube:1c6iany7]

We had smaller pools for years but when we wanted to install the big pool, we made sure we did it right. Never take shortcuts or you pay later.
 
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