laying insulation for floor questions...

[Paul-man]

We will soon be having our sand cement screed laid and it will have UFH within.

We are trying to choose our flooring in advance so that we can get the screed laid to the correct depth, so i have posted some similar follow on questions in the flooring forum. However, I think the first 2 are best placed here....


1) I will be painting "BlackJack" onto the existing (garage) concrete floor and up the walls as far as the existing DPM. The existing DPM in the wall is at the height that we want our FFL so that there is no step between the two rooms. Is it a problem that the screed will not come as high as the old DPM? (Currently, I have a step down of 2 courses of brick.)

2) Should I put the insulation upstands to the height of the desired FFL or to the height of the screed?

 

[mointainwalker]

2) Should I put the insulation upstands to the height of the desired FFL or to the height of the screed?

Presumably you are only talking about a cm or so and since it will only take about two minutes to cut off any excess insulation, why are you worrying about it ?

 

[^woody^]

You should be working down from the desired finnished floor level and not up to it.

So you allow say 50mm of screed, see what is left and then decide if you need to use thicker insulation, a bit of concrete or just thicken the screed

Perimeter insualtion is to the finished floor level

Bear in mind that Celotex type insulation is twice as efficient as normal polystyrene - ie you need 1/2 the thickness

I'm not sure about your 2) comment as the FFL is the screed height

 

[freddiemercurystwin]

Bear in mind that Celotex type insulation is twice as efficient as normal polystyrene - ie you need 1/2 the thickness

You naughty Boy ^woody^!

 

[^woody^]

 

[Paul-man]

Thanks Woody. I had mistakenly understood FFL to be the final finished - ie with the wood flooring on top.

My builder, who is doing the screed is going to match the screed height to the original, which means that half of my original questions are solved.

I have however cut the insulation to screed height - in line with the top of the DPC. Had I realised it was so easy to cut with a Stanley knife I wouldn't have worried! (Though I have 16 pieces to adjust if it is wrong!)

I will have to try and lost the height difference between the floors by using a thinner wood floor or a threshold worst case scenario.

Will try to post some project photos of my work in the project forum soon for anyone who is interested!