Water proofing damp concrete floor

[philly1]

Hi,

After lifting the newly laid laminate in one of the bedrooms of my 1950s bungalow, noticed very damp/wet tiles underneath (which were bone dry a year ago when renovating) - see photos 1 & 2. I have painted layers of Wickes liquid DPM over the left over bitumen adhesive that was under the tiles hoping that this would stop the damp - see photo 3.

However, I laid the new underlay a couple of weeks ago but never got round to relaying the laminate and noticed the musty smell was back. It now looks like mold growing on top of the liquid DPM under the underlay and feels wet to touch! Not sure where to go from here now as nothing will stick to this stuff other than a 50mm layer of cement apparently which i'm guessing will just have the same problem? Could I lay a physical membrane over it and use self leveller over that or would it just lift?

Any advice would be much appreciated as my 2 year old is currently sleeping in our room, my wife is getting impatient and I'm slowly declining into despair!!

Thanks,

Phil

 

[theprinceofdarkness]

You will have to explain the pictures to me. The two with the tile marks on. I presume the "blobs" in the centre is where the bitumen was? It looks as though the dark wet marks is where water has leaked through from the top via the joints. You are saying that the damp is rising through the concrete. Have you checked for the soil level outside and the quality of the concrete?. Its very funny that this dampness has not soaked up the walls, thats what rising damp is meant to do! Clutching at straws, its not condensation caused by having a large uninsulated slab of impervious concrete sitting in your nice humid and warm room , is it?
Frank

 

[joe-90]

Not much else it could be. Nothing is going to come up past the DPM if it is intact.

 

[philly1]

Hi both, thanks for the replies. The first 2 pictures are of the tiles before I took them up. The water marks are the damp coming up in between the tiles. The last picture is the floor with the liquid dpm painted on.

So you think it was probably just condensation gathering under the underlay making it wet? Would this happen less once I've put the laminate floor down and less air can get underneath then or would this still occur? (I don't want to put the floor back if it's just going to harbour mold underneath)...

 

[philly1]

P.s. The walls are made up of the solid engineering bricks which I think are more resiliant to rising damp (or did I make that up?!), and the concrete was good condition before painting - just a couple of very thin cracks which I cemented over first. Ground is lower outside but very moist (on a hill with a high water table I think)

 

[ree]

Pic 1. shows a hefty looking membrane that was laid over the tiles. Is this "BARRIER" simply a stand alone sheet or is it integral to an underlayment?

If the cause was condensation then the moisture would collect on top of the BARRIER not below it on the tile.
If the cause was condensation then it would have shown its hand before any barrier or laminate was laid.

I would suspect that the moisture is coming up from the slab because the slab is not enclosed by a DPM. Your 1950's house possibly didn't have a DPM
The "high water table" & the hillside position suggest that gravity is forcing the ground water up.
The ground floor of the house could actually be below the level of the water table.

Perhaps the warmth of the room was evaporating the rising moisture a year ago when the floor appeared "bone dry"?

OP, can you post pics of the external wall?
Do you have a retaining wall in proximity to that wall?

 

[ree]

philly1,

And?

I'm wondering where your reply is?

I'm also wandering where any pics of the outside of the external wall area are?

And to cap it all, i'm certain that a hillside site with a high water table must have a retaining wall but you are the only one who can confirm or deny?

Perhaps your two yr old, yourself & your wife are now resigned to damp? How quick a mood can change?

 

[philly1]

Hi Ree, sorry, wasn't being ignorant, I didnt get a notification of a reply to your last post for some reason! The "barrier" was integral to the underlay. You can see the new 'Gold' underlay I've bought on the left in the last picture which also has an integral moisture barrier. It was under this that the new mould growth appeared since painting the liquid dpm, although this was just 'loose' on top of the floor with no laminate on top. Typically, it hasn't rained since so I'm still waiting to see if this reoccurs.

Yes, there is a retaining wall with a drive on top behind this room - see attached. The french drain has puddles even though no rain and there is moisture seeping out at the bottom of the wall.

After further reading, the instructions for the liquid DPM say that a 50mm layer of cement is required on top of it to withstand the pressure of the rising water (the instructions dont say the reason for the 50mm of cement and the helpful man in the shop said 'nah just laminate over it will be fine'). I can't raise the floor by that amount so bit unsure where to go from here. Was thinking maybe I'll get away with an SBR/cement slurry to make it stronger and add to the water proofing?? I'm close to giving up now and getting a damp proof company in to rip me off... I mean help...