Lee Nowell wrote:
Hi All,

A friend has an old indoor swimming pool which he got converted into a
playroom. They removed the inner lining and constructed a deck over
the pool enabling him to use the old pool below as a good storage
area. This worked a treat until the winter rains came and it
transpired that the water table is very high and the pool was not
tanked on the outside. Net result water is seeping into the storage
area and stinks!!

Ordinarily, he would fill it all in then finish with a DPM and
concrete slab but this is going to cost a fortune - mainly because of
access/ distance issues to transport the gear to the pool. As a
cheaper option, a builder has suggested dropping the timber deck 100mm
adding some DPM/ sealant on top of it and pouring a 100mm slab of
reinforced concrete. I guess he would have to dig some of the edging
away to ensure the slab sits on the pool side walls. Would this
approach work?


No.
The timber wouldn't last more than a few years, no ventilation, constantly
damp from the pool water etc, and when it rots away, the slab above is
spanning the entire pool without support


My initial thoughts were...
1. water will still come in below the decking as normal but in theory,
you won't smell it if the slab is fully sealed - seems likely to fail
in the future.
2. during the wet months, water will come in from the "force" of the
surrounding water table. Will this go away in the drier months or just
sit there? The side walls are made of concrete blocks. Even if it
does seep back into the soil, won't it leave a horrible slimy residue?


I think he needs to decide whether he wants to keep this as a storage space
or just cover it up once and for all and forget about it.
If the former, he'll either have to pay out for tanking, or put up with the
water ingress and associated smells, etc, if the latter, and he can't afford
to get it filled, he'll have to cover it up properly.
Concreting over wood is useless for the reasons mentioned earlier, steel is
slightly better but also liable to rot / expand / both.
His other option is to use concrete beams laid from one side to the other
with blocks inbetween (block and beam*) and then concrete over this, you
don't mention the size of the pool, but he may need to build a wall in the
centre of the span to hold up the concrete beams, although this may well
work out more expensive than having it tanked.


* http://snipurl.com/10h1ei

--
Phil L
RSRL Tipster Of The Year 2008