Damp Garage Floor/Walls - Any advice welcome

[lozinger99]

I’ve had my garage re-roofed but still a problem with damp penetrating the floor.

It’s a large single skin brick built garage with 18mm ply decking and EPDM roof. So the garage is definitely as dry as it will get (post re-roof) but there is still damp patches emerging through the slabs and where the side walls meets the floor.

I’d like to use it as a bit of a utility space so am prepared to put some work into removing as much damp as possible.

It is a slab base and knowing the bloke I bought the house from, almost certainly has no DPM underneath, same with the walls.

One problem is I’ve no access to the sides of the garage as it runs form garden to garden (soil on both sides) So I can’t really do anything in terms of adding any drainage or DPC on the outside.

So, what to do….

I’ve had a few ideas…tank the floor, then put some sort of poly sheet over this and then lay rubber tiles on top…

But I’m not sure what to do about the walls. Take the walls, run some sort of DPM across the floor and up the walls? ID rather not batten the walls in any way as space is at a premium.

To add a little added complexity, the floor is also sloped and could do with levelling. So not sure to do about that either in terms of DPM first, levelling compound after?

Many thanks in advance for any help as its making my brain bleed

 

[ree]

Your neighbour's cannot allow soil to build up against your garage floor - discuss with them and see if any high spots can be lowered.

The 18mm ply decking is presumably simply sitting on the concrete - is it water damaged?

Perhaps lay a membrane to lap up the walls a little, and then re-lay the ply on the membrane, or drop some 2" x 4" wedged level joists onto the membrane (nog them together) and (leaving gaps at the edges for ventilation) - then fix the ply to the joists?

 

[lozinger99]

Hey Ree,

Many thanks for the reply

Yeah, the soil isnt really my neighbours fault as such , more that the guy who built the garage built it right up to their gardens (ie removed the fence) and as such the garage forms the boundary where the fence would have been, so it just their garden basically - not sure how he got away with that! So its grass on the far side and flower beds on the other - which snookers me from doing anything that way.

Sorry the ply was referring to the type of roof it was. The floor is just slabs at the moment, to make matters worse someone at some point has tried to level it, and only did half a job so its slabs, a random bit of concrete, and to complicate matters further it is sloping in at least two directions.

If I manage to flatten it, do you think the lapped DPM sheet as you suggested, underneath any floorign I put down would be enough to stop the damp rising up?

The damp patches appear though thick stone flags and all along the wall/floor joints so although not really watery , still quite significant.

I was hoping to used rubber tiles in there as i have weights bench in there. Although I think as you suggested it may be easier to have joists.

 

[ree]

Your post is a bit weird, things keep changing.

Anyway, yes, put down some membrane and set to level some joists then screw some cheap boards/sheets on top.

It will be trial and error to construct and who knows how effective for how long it will be?