Self Leveller and DPC - Help

[bobby5000]

Hi all,

I am getting the scuffed old concrete floor in my lounge levelled with screed. There is a gap between the floor base and the walls. You can see, in the photo I've attached, the DPC running through the wall an inch or so below the existing finished floor level.

If the self leveling screed is allowed to flow into and fill the gap between the floor and wall - making contact with the bricks below and above the DPC - I am worried that this will see the screed bridging the DPC and later causing damp problems up the wall.

How would you prevent this from happening?

- could pour concrete into the gap first? If the concrete is waterproof, otherwise same problem...

- use a foam roll type of barrier around the edge. I am unsure whether such foam roll is able to absorb water or not.

- use a waterproof screed?

On the other hand, is it better to not fill the gap at all, and try to just keep the new screed strictly on the existing floor surface? If so, how?

Thanks!

 

[^woody^]

Fill it with a liquid DPM

 

[bobby5000]

Fill it with a liquid DPM

Alright mate, thanks for response.

So would you fill the whole "trench" with liquid DPM, so it rises above the DPC and is then level with the floor surface? Then screed over the lot up to the walls?

 

[^woody^]

Something like that!

Or expanding foam (there is a low expansion foam product which may be better than the normal type), or foam strip as that will remove the cold bridge against the wall.

The skirting will cover most of it.

 

[bobby5000]

Something like that!

Or expanding foam (there is a low expansion foam product which may be better than the normal type), or foam strip as that will remove the cold bridge against the wall.

The skirting will cover most of it.

The problem in my case is that the trench is at least a couple of inches deep in places and the DPC is visible within it below the floor level.

Would the liquid DPM stuff result in a cold bridge if just used to fill up the trench?

With the foam strip, would you be putting that against the wall, and DPC line, from the bottom of the trough and then pouring the screed in to the trench? Only concern then is how water resistant the foam is...

In terms of this cold bridge issue - don't most houses just have the floor going right up to the wall? I can't figure out why there's a gap in mine.

 

[Mr Chibs]

You are overthinking it.

Expanding foam to fill trench, once set, cut off the excess with a saw/knife flush to old floor, then new screed/slc on top.
You could apply foam expansion strip similar to UFH before you apply screed, although not necessary.

 

[Diver Fred]

You could apply foam expansion strip similar to UFH before you apply screed, although not necessary.

That's the way to do it.