How do I use a damp proof membrane under self levelling compound in a garage?

Kinkajou

Dear Moneysavers, I have a garage at the back of the garden that I would like to use for storage and to exercise in. It has an old dusty concrete floor and a little bit of dampness on the side of the floor adjoining the access road at (a width of about 1inches). Walls appear to be dry & are mainly concrete block.  I wanted to self-level the floor using mapai ultimate leveller 1210 and Secrete Ulitmate Primer for adhesion.
If I put a damp proof membrane  down first, like a paintable one like Wickes paintable bitumen or Drybase Dpm in white, would products like this work under self levelling compound?  I bought 16mm deep rubber gym tiles to finish the floor. I tell you, I've used muscles I never knew I had over the last few weeks just cleaning out the room. Thanks!

gwynlas

Our builder used the paintable dpm followed by 60mm celotex and loose laid ply on top. Floor layer followed up with S101 ply and stuck down vinyl tile

Kinkajou

gwynlas said:

Our builder used the paintable dpm followed by 60mm celotex and loose laid ply on top. Floor layer followed up with S101 ply and stuck down vinyl tile

Thanks so much for your reply gwynlas!  Did your builder cover the entire floor or just the damp area? Thanks!

Kinkajou

Hi Moneysavers!  Thought I'd give an update. I think I have gone a step too far in my money-saving efforts.  I used Black Jack DPM over the garage floor and the bottom of the wall up to about 5 inches.  Now the damp that was previously being sucked up by the porous concrete floor is now sitting on top of the floor in a couple of puddles after a night of heavy driving rain. I'm very upset with myself, I was only trying to be proactive and do things myself as I have had a few cowboys in the past. I had hoped to put a self levelled floor over this, but now I've halted this plan. I am not sure of the source of the water, the roof and walls don't show dampness at all. It's time to call a damp specialist I think.  😔 

FreeBear

If water is pooling, then you have a leak somewhere. Start looking at the roof above the puddles - Any cracks, holes, or ill fitting roof sheets up there ?

The water may be getting driven in under a gap at the bottom of the main garage door..

gwynlas

We occasionally had damp patch on floor but this was from a leak in roof as yours appears to be rather than damp rising from subfloor. There was little evidence of leak just slight  marking of joist where water had tracked

Kinkajou

Dear FreeBear and gwynlas.  I feel so much better after reading your helpful replies! Really appreciate it, as I was feeling down.  I will do some investigations tomorrow with the ladder. Some of the rain could well have come in via the service door as it is broken at the moment as it not closing properly ( I have another door ordered). Wish me luck! I'll update shortly👍 Thanks again.

FreeBear

Had a thought on checking for leaks from the roof. Spread a sheet of plastic out on the floor and weight down the corners. place some sheets of newspaper on top. Next time it rains, look for damp patches on the paper, then look straight up - This should give you a rough idea of which part of the roof is leaking and also rule out water coming up through the concrete.

Gastines3

I always used to use a Latex -mix flooring screed when in the flooring trade and found that was the best fix for dust and damp..

Kinkajou

Thanks, Gastines3, FreeBear, and gwynlas!  Well, I called a damp proofing guy in, he had a look said if it was him he would put in a screed at least 2 inches high and concrete outside.  Said he'd provide a quote but didn't come back to me.  So, as money's too tight to mention round here, I replaced the leaking door with a cheap UPVc one. Freebear, you're right, some of the water was blown from the old door that couldn't close.  I mixed some concrete, removed the moss, and built up around the side of the garage at the outside with the concrete, and filled in some deep holes.  Inside I put flashing around the walls also laid my first self leveled floor using Setcrete Deep Base.  Not bad for an amateur, it rained a few times & garage stayed dry- happy days. BUT - last night's torrential rain shows there are still some leaks, it seemed to seep through from the outside and over the top of the flashing onto the floor inside. Very frustrating!. But not half as bad as it was previously.  There is a huge puddle outside on the road corresponding to where it's coming from, so on the next couple of dry days, I'll be outside again with more concrete.🙄. Just wanted to update. Thanks if you've read this far!😀

531063

If you spread talc powder on the floor you will see if water is running in through a trail in talc, give you idea of which direction to look in