I’ve got a project where the owners have an indoor swimming pool that they don’t use much anymore and want to turn the space into a master suite. The room is about 24′ x 36′. The pool is gunite, the pool deck ceramic tile over 4″ reinforced concrete, all surrounded by a 12″ high foundation wall.
My thought was to leave the pool and spa in place, drain the water, drill a few holes in the bottom to relieve any hydro-static pressure that might be present, and then frame a typical wood-joisted floor over the whole thing. I’m wondering, however, about access to the underfloor area……… Flooring over the existing deck and pool areas will not leave enough room for access should the code require it (which I’m not exactly clear on). If there is no plumbing, electrical or mechanical in the underfloor area, why would it need to be accessed? It seems an enormous waste of time and money to demolish the existing concrete decking and excavate down to enable the typical 18″ underfloor crawl area usually required in our area.
Anybody done a similar project or have any input?
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My only Q would be that if theree is a valid reason to fear hydrostatic pressure, you may end up with a foot of water in the bottom after drilling those holes...
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I don't think there is a reason to fear hydrostatic pressure, but did a project years ago where we built over a pool (outdoor), and were required to cut holes in the bottom of the pool and fill it with engineered fill before proceeding. The reason, we were told, is that the pool might "pop out of the ground" without the weight of the water to keep it in place. Never seen a pool pop out of the ground...........
I ran this question informally by a couple of local inspectors. One said yeah, cut holes in the bottom, the other said don't bother.
What's your take on the underfloor access?
I'd fill it with gravel, then cover it with vapourstop, then build away.No need for access, I have done several without it. I do see pools that jump up out of the ground though. It is when owners allow them to be empty in winter. Frost starts them up and out, then water runs in under in a wet spring and you have a boat floating on the water
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I've heard tell of poppin pools, but never seen one. In our area (PacNW), it never gets cold enough to freeze the ground more than an inch or two, and with the global warming and all, nothin to worry about.
Thanks for your input!
But you do get rain. I would to at least know about ground water cinditions and perimeter drainages. Maybe sinka a sump pump and have access for it.
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Yeah, you need some sort of weight in there, unless this is the desert. Punch holes in the bottom, fill part way with gravel/sand, and top with a vapor barrier would seem to make sense.I'd try hard to figure out an access to at least the actual pool area.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
> Never seen a pool pop out of the ground...........I saw it happen once in Florida.George Patterson, Patterson Handyman Service
Redfly
I worked for a guy in Austin TX that did exactly what you said regarding the pool. I think he had to break something like 30% of the floor up and then fill with some specific material, dont recal what it was.
I wouldnt want to just go filling a pool in without breaking the bottom out.
Why cant you do a concrete pad over the top of the fill, then you'd need no access to the underside.
Doug
It is the unknown part of this equation that concerns me. If you do this, it seems like you could be setting your self up for trouble down the road.
And, I can't imagine this would pass code unless you have compromising pictures of your local inspectors.
- Colin
Colin,
I do want to avoid 'trouble down the road', but I also want to avoid spending several thousand $$ of client's money to demo and excavate if I can safely avoid it. I see the situation as very similar to building a room over a garage slab except that the slab is 8" below the floor in some places and 8' below in others. What is it about the situation that would make you uncomfortable - the pool or the inaccessability? I can't seem to find anything in the code that addresses this particular situation, which is the reason that I'm asking for input. Our juristiction is pretty small (only 2 plan checkers and 1 building insp), so the question of whether they would approve my plans depends somewhat on how I present it and somewhat on the mood of the particular plan checker at the time of presentation, but I like to be be pretty sure of my ground before I submit. Any I definitely would not build anything I suspected was in violation of any code.
I don't have any direct experience with this, but do have a pool and the installer told us that we should never drain it completely as hydrostatic pressure might cause it to pop up or whatever... Personally I wouldn't drill holes in the bottom for fear of it filling up with water and turning to nasty muck. My idea would be to fill it with sand. I guess gravel would do the same thing. You might want to figure which is cheapest per yard...
Regarding code, I don't see much difference between what you are proposing to do vs laying sleepers or even joists on say a garage concrete floor to turn it into a heated space. Like you said, if there is no electricals or HVAC down there, no access is required.
One possible gotcha could be that if you span the pool hole with, say 2x10s, they need solid support at each end of the joists. Does the pool deck meet this criteria? I don't think so... For all the inspector knows, the pool deck could be 1.5" thick... Also, even if the pool hole was filled with say gravel all the way up to the bottom of the new joists, this still couldn't be considered load bearing support, because the substraight below the gunnite is an unknown.
Just thinking out loud here...
I don't plan to bear anything on the pool surface or pool deck - the joists would be supported by the perimeter foundation and a mid-span beam, which would bear on new footings poured through the pool deck and bottom. The 'soil' in our area is mostly rock, and there is no water table to speak of. One reason for not filling the pool with gravel or sand, etc., is that if I do, it would need to be engineered fill (read $3-$4,000) to bear the weight of the post footings. One the other hand, if I cut throgh the bottom of the pool and pour new footings, I could post up under the beam with treated lumber and be done with it. I understand your comment about the pool filling up with water, but don't feel that would be a problem given the local condition. Of course, the building dept may require that anyway, so the question may be moot.
My reasoning of filling the pool was not to create any kind of bearing surface, but rather just to fill the void with a drainable material that was heavy enough to hold the pool in place in the event there was some kind of under ground pressure.
Here's an idea - if that were mine, I would be interested in knowing if I could convert that space to a safe room
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"safe room"? you must know something I only suspect.
visions of 1962 dance in my head..........
I just know they are becoming more popular
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Why waste the space........
safe room = storm cellar
" " = wine cellar
" " = conditioned closet
" " = fallout shelter
" " = valubles vault
" " = gun & ammo magazine
" " = B&D chamber
It would be really rare to have an indoor pool "pop' and the sump pump is a good thought as a preventative measure.
That leaves the question of access and the current room plan...!?
.............Iron Helix
You wouldn't need engineered fill. It's just backfill that you put in after your footings are in place.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
OK, here's what I think I'll do:
Cut holes in the pool and deck for footings for my mid-span beam supports, install PT posts under the beam, fill the hole with gravel or whatever is cheapest, lay plastic over it and build the floor over the top - shouldn't need access (with only about 8" of clearance.
Thanks everybody for the input!
Would it be that much more effort to make it a basement?
I think it's the stairway in the middle of the bedroom that's the problem.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Murphy bed! Swings right up
Just down the road a bit at a motel, someone did just that.
Years later, somehow a propane leak developed inside the motel, close to the pool.
Guess where the heavier than air gas accumulated?
Guess what happened in the morning when the maids fired up the vacuum?
Be careful.
[email protected]
Interesting point.
Another reason to fill the thing in.
I'd think the ideal fix would be to fill it with compacted road base or sand and pour a slab with rebar tied into the existing slab. The floor will feel more consistent than if half wood framing and half concrete. If a wood floor is added it would be better to add enough road base to be above the ground water line and pour a footer over it at mid span for a pony wall to stiffen up the floor to more closely match the slab around the perimiter.
What type of flooring is going in there? I'd be hesitant to use tile with a half wood floor because the transition between the two would be likely to move due to uneven expansion/contraction.
Beer was created so carpenters wouldn't rule the world.
If your subteranean water level is anywhere near the bottom of the pool even during a rain storm, it'll float up until it hits your joists, then it all depends whether your floor is heavier or the pool more bouyant (my $ is on the pool). Maybe not right away but it will work it's way out of the ground with no weight in it.
Drilling holes just allows the water to seap in and then get stagnant under your floor.