Damp patch on concrete floor by door

8 Mar 2010
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United Kingdom
I have a damp area by my upvc french doors.

There is a crack in the concrete floor approx 16cm from the doors. In this crack I can see what I presume is the plastic floor dpc? I've attached a picture. Should this run all the way up to the door?

What can I do to resolve this? I was thinking of painting the whole area with liquid dpm. The skirting is touching the floor so i was going to trim the bottom of this so it doesnt. Do I need to remove it and paint the wall with any liquid dpm as well?

I have attached pictures:

Thank you in advance.

View attachment 286409View attachment 286410

View attachment 286411
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Always a problem to us this. Dpm sheet isn’t under the door frame correct.
I would dig that section out and put in a Dpm sheet then fill with ardex NA and granno chips.
Thank you for the reply.

How far would you dig down? Chips in first then ardex on top I presume?

Do I need to put the sheet up the walls at all?

Sorry for the novice questions
Dig down around 6 inch.
You mix the ardex NA then add the granno and mix that in as well. You can use other latex screeds but make sure it’s a bag and bottle and not a water mix.
you leave the Dpm sheet up the sides around a inch
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I guess I'll need to take the skirtings off to get the DPM up the wall.

There is what I think is the inner cavity wall blocks on the window side of that big crack. Do I leave these as are and just dig out the wall cavity? How would I join the new dpm against where it meets the old one?

On the door side, I guess I bring the dpm up the 6 inches I've dug and try tuck it as far as I can under the door frame?

Is this the stuff you mean? Is the granno just to bulk it up?

Thank you for your help
Last edited:
Yes that’s it. We use 6mm granno from a builders yard.
I put it up the frame in front of the door then when it’s all the screed is set cut it 5mm above the floor Level. Then silicone it or use quadrant.
what you want Is no moisture can get into the screed from the bricks.

you can joint the sheet with moisture tape
You can use normal concrete. We just use NA as we need to get on it and carry on with the job the same week.
Ive got the ardex for this job, about to start it in next week or so. The ardex instructions say its only to be used 30mm deep when mixed with aggregate?

I know you said 6inchs in 1 go is ok but just double checking. How long would it take at 6inch depth to before i can lay carpet back down?
Done it loads of times and never had a problem. You could lay the carpet after 3 days I’d say. It goes light grey when dry
Just to update, I finally got this job done this week. Followed your instructions and all went well.

I can't believe it was built this way or not picked up on when the house was built 25 years ago.


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