The Brew Cabin

I have a problem with large amounts of ground water that come up through concrete floors in old stone outbuildings. The ground level rises behind the buidlings where the water seems to be coming from and I have previously dug a 600mm trench with perforated pipe / clean ballast to catch / divert groundwater.

This has not helped (my Missus swears it is worse!), the water still rises when it rains.

The problem is that I would like to take up the old floors and put down new (other neigbouring buidings have similar problems but only have soil floors) concrete floors in all of the buildings but I would lke to either cure this problem once and for all or lay the new floors in such a way that the water passes harmlessly underneath and does not make an appearance on the surface.

Is it possible to seal the floors to this extent? I am worried about forcing the water to rise up the non DPC walls or squeeze its way through the inevitable crack between the wall and the floor (I could seal this with mastic jointing compound).

Alternately am I talking a cowboy job and would be better served solving the drainage problem (I bet this is expensive)

There's a few possible solutions to this problem, but they all require a deal of work that is probably best left to specialists, as, one leak and the whole thing fails. :(

An extended version of the Dry Area Arrangement is one option, and you would need to incorporate a collector drain at some point on the ground side of the channel. The key point would be to get the base of the channel to a level below that of the intended FFL inside the buildings.

Alternatively, a vertical drainage composite linked to a fin drain or other outfall might be a better option.

Sealing the floors is a non-starter, I'm afraid. It would simply force the water, which is driven by hydrostatic pressure, to find a new weak point which would more than likely involve wicking up through the walls, making matters a whole lot worse.

As with many of these problems, I can't say what is best as I can't see the site and take into account all the relevant factors, which is why I recommend you get a drainage specialist of a damned good groundworker to take a look and advise you on site. It may be that they, in turn, recommend a civil or structural engineer to design a solution, which won't be particularly cheap, but would be money well spent, as it's virtually guaranteed to rectify the problem.

Good luck!