Liquid DPM on cement

12 Jun 2005
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United Kingdom
First I want to apologies for asking the same question that's been asked over 100 times in a hundred different ways with lots of different answers but I just want to be 100% sure before I proceed.

I live in an ex-local authority house, back in the day to stop the terraced houses burning down the ripped out the wooden floors from the kitchens and filled them with cement, but neglected to install a DPM (I don't know for sure that they didn't, I just think it's unlikely they did).

Today the floor has a 2cm thick covering of bitumen/asphalt. However through various building work that's gone on, a 3m square section has been damaged and cracked.

Generally the advice I've found has been "if it's in, like it or not, leave it alone."

I've read the post on how to install a surface DPM //

I've looked at the F-Ball and Ardex alternatives although the solutions seem to be designed for use in the building trade, on new floors that still contains moisture, F-Ball/Ardex liquid DPM is then put on it so building work can proceed without the moisture damaging anything that's going to be put on top of it. Which sounds to me like these are temporary measures and not something designed remain an effective DPM for the life of the building.

I want to rip out all the old bitumen/Asphalt then use either the F-Ball F75 or the Ardex 2 coat DPM to cover the floor, prime it with ARDEX WPM 200 or an F-Ball alternative before covering it all in a latex based self levelling compound.

Has anyone used any of these products in this kind of scenario and are they effective?

Living with the asphalt would have been better but with the damage I would rather rip it out, put down a liquid DPM and tile the surface.
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You can patch repair asphalt easily.

Use say Synthaproof as a primer on a clean squared off patch and after a few of coats of synthaproof you can level it off with whatever material suits you depending on what the finished floor material will be.

Why rip out a good material - if its uneven then SLC can be used over the asphalt.
You could leave it down then go
Ardex NA
Ardex DPM1c
Ardex NA

Or rio it out and do same but you will need more screed to build it up.

Or do same using f ball Products like

Stopgap green bag / 114 liquid or stopgap 1200 pro

2 coats f75 or 1 coat F77
Thanks for the advice, I'll weigh both options up, if I can patch repair and be sure that it will hold I will give it a try.

I want to tile the floor eventually so reducing the thickness (currently 2cm) would be ideal.
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Asphalt was originally laid as a membrane (DPM) - retro or on new build.
Remove it and a new membrane - sheet, liquid etc - will be required.

Asphalt was often used as a screed to level off an uneven surface.

Will you be working with a "dry fit" kitchen space ie. no units or apps, or with them in place?
hi Ree

Thanks for the reply.

The lot is coming out, kitchen unit's, tiles, cooker, skirting boards, architraving and all appliances including the fridge.

right the way through to the downstairs toilet.

It's split into two area's one I will make a utility room, the other the main kitchen.

I was thinking of taking up all the Asphalt, removing the plaster from the bottom of the walls, about 4-5 inches high, putting down the liquid membrane and bringing it up the wall about 3-4 inches before putting down the self leveling compound.

Replaster the bottom of the wall using a higher content of lime, then tile the floor.
Sounds fine, go ahead if you are happy with that method.

Keep your re-plaster above the slc by a 50mm min.

What will the finished floor material be?

External ground level, and any need for any remedial measures should be checked for. If you encounter any damp in the walls come back here.
Sounds fine, go ahead if you are happy with that method.

Keep your re-plaster above the slc by a 50mm min.

What will the finished floor material be?

External ground level, and any need for any remedial measures should be checked for. If you encounter any damp in the walls come back here.

Thanks for the advice on the re-plaster.
I plan to lay terracotta tiles over the screed.

Externally I have noticed a deterioration of the brickwork, mainly some flaking in parts and the appearance of saltpeter.

I was going to clean it all off and wash it with a vinegar solution then use a suitable water repellent for brickwork but thought I'd get the floor done first as I suspect thi is the origin of the damp, so think this would be the best way to finish it off.
Be aware of where your FFL will end up in terms of adjoining rooms and doors. Use good quality quarry tiles - they can wear quickly on traffic patterns.

If there are any other damp issues with the walls or externally then come back here - i assume you have cavity walls?
OK so I finally got around to doing this.

There were some wooden battons at the base of the walls so I took them off so I could come up the wall a bit.

Kept it simple.

3mm of Arditex NA first
top with the liquid dpm, coming up the wall a couple of inches, before a final topping of the NA.

I'm really impressed with the stuff, but what I didn't realise when embarking on this, was that the DPM gives you 20 minutes of work time, which was eaten through by the time I was over half way.

I had considered getting two tins especially after watching this video which for me highlights the importance of putting the NA down first.

This thread here was also helpful although I think with a 3mm V notch trowl in my inexperienced hands I still managed to get it on too thick.

In the end I got the whole tin down, but because of my lack of experience using this stuff I was 1 sqm short of covering the whole 15sqm with it.

Someone more experience probably could have done the lot in probably 20-25 minutes and to the correct thickness.

However there are no thin patches or trowl groves so I'm pretty sure it's sound.

If anyone else wants to attempt this and it's more then 13sqm you need to cover, I would suggest this.

1: Get someone in that's doe it before.

2: If you're inexperienced or have a large area to cover.
A: Consider 2 tins and go as far as you can, then you should have enough to touch up any bear spots and finish the rest with a bit more time to ensure a good installation.
B: An extra pair of hands
C: Both A & B

I managed to get hold of an extra 6kg tin locally off ebay for £40 so got lucky and could finish it the next day.

Planning to get some indian slate for the floor.
It seems cheaper than the quarry tiles from topps (150x150) and would cost £500 but I think I could get slate for half that price.

I know what people say about the variations in size and thickness but reckon if I do it right it should look good.

If I ever sell the house I don't want them thinking about taking it up.

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