Jon Weaver wrote:

The Natural Philosopher wrote in message ...

Christian McArdle wrote:


Where would the insulation layer go, ontop, or under the DPM?


AIUI, on top of the DPM. Someone more knowledgable than me will suggest the
exact ordering and thicknesses. However, I suspect 50mm of Jablite would
make a real difference, and 30mm of screed might work on top to make the
original thickness.

Christian.




Actually it makes sod all difference where the DPM goes. Above or below
the insulation. I asked teh architecet, and he just shrugged.

I put mine ABOVE for the imple practical reason that it wouldnt get
puntured on teh rather rough surface underneath - the insulation is very
good as covering sharp lumps

50mm blue/pink foam is excellent. 75mm is even better. At LEAST 75mm
screed, and more if you can fit it in.


My problem is that the current 'slab' height means that it will be
impossible to raise the floor by any more than 100mm.. So, If I have
to add 50mm of insulation and 75mm of screed, the only physically way
possible would be to lower the slab by 25mm, and as you will imagine,
this impossible.

A colleague of mine (who is building his own house) has suggested that
I go for 50mm of insulation and 50mm of screed, but use a steel mesh
to re-enforce the screed.


Mmm. Actually for reason I'll explain, I'd use chicken wire.

The problem with thin scred over insulation, is that heavy pinted object
- chair leg etc - over a small area could compress the insulation and
crack teh screed. So you want a lot of local reniforcement rather than
overall reinforcement. Chicken wire or the sort of mesh that used to
render over on walls etc would I think be better able to do this.

Try and use the insulation if you can. If you slate or laminate the
floor afterwards that will also help load spereading.





My other option of course is to forget ever having asked the question,
and go along with the plan WITHOUT insulation.

If I can get away with 50mm of each and a steel mesh, I might be
tempted to get the bits that I need and ask the builder to do this
when he lays the screed at the weekend.