R. Cott. 16

Anyone any experience of dry screed overlay boards?

Claim to have 4 times lower thermal resistance than equivalent chipboard and look easy to lay (just glue the joints).

Price looks a bit steep at roughly 4 x moisture resistant chip!

Reply to
Tim Lamb
Loading thread data ...

All they are, is a rectangular chuck of Fermacell (or Knauf Brio equiv.) bonded to a layer of extruded poly, with offset edges to allow each board to over/underlap the ones at its four sides. The joints are fixed with something like gorilla glue and screwed.

You could achieve the same with a layer of celotex or similar and then overlay with 22mm T&G plywood like caberfloor.

Dont forget the 10 mm expansion gaps all around else it WILL buckle up.

You cannot put hardwood flooring on top of the Fermacell or Knauf BRio stuff because it is gypsum and cellulose based and the expansion and contraction of the timber flooring scrubs away the gypsum (eventually).

Reply to
Andrew

OK. I was just thinking it would improve the response time of the underfloor heating and might allow an eventual move to air source.

I expect I'll stick with the 18mm chipboard.

>
Reply to
Tim Lamb

What is between the UF heating pipes and whatever you finally walk on ?. Normally the UF heating pipes would be slotted into the Fermacell or Knauf Brio, possibly with heat spreaders to distribute the heat and then overlaid with engineered flooring.

if you are putting chipboard on top of UF heating, what protects the UF pipes from being crushed ?. Or are they slotted into pregrooved slabs of insulation ?.

Reply to
Andrew

Papercrete makes a cheap insulating floor screed.

NT

Reply to
tabbypurr

You and Andrew are not talking about te same thing.

Does '4 times lower thermal resistance' mean they are good conductors or good insulators?

Reply to
The Natural Philosopher

Better thermal conductors than woodchip:-)

We seem to be obsessed by the *insulation* properties of building materials.

I wonder when building control will start worrying about the impact of house fires on the PIR foam they are pushing us to cram in to wall and loft spaces.

Reply to
Tim Lamb

Ground floor is to be grooved polystyrene with a foil spreader surface.

Sadly the existing oversite is not otherwise insulated.

Reply to
Tim Lamb

about 14 June 2017 I think.

Officials have begun preparations for a major review of building regulations in England, Newsnight has learned.

formatting link

Owain

Reply to
spuorgelgoog

Tiles are tradional

I've also used engineering laminate.

but 18mm chip is not a bad thing either.

Reply to
The Natural Philosopher

Presumably you're looking at improving the under floor cooling performance where such a fourfold reduction in the thermal resistance would be beneficial.

Reply to
Johnny B Good

This confused me at first, but I think he wants to put the boards on top of underfloor heating, so he *does* want improved heat *conduction*. He described it as UHF, which took me time to interpret.

Reply to
Roger Hayter

^^^ Well I misread UF as UHF and confused myself, apparently.

Reply to
Roger Hayter

My bad! I was concentrating on the more common passive underfloor insulation aspect to reduce heat loss / cold spots in a conventionally heated room, forgetting that reduced thermal resistance works *both ways* (and in particular, a benefit with UFH).

As is usual for me, this aspect didn't occur to me until *after* hitting the send button and spotting the follow up postings which would have saved me the embarrassment of misconstruing the OP in the first place! :-(

Reply to
Johnny B Good

According to page 44 of the Fermacell handbook - "Fermacell dry flooring is laid on an existing structural floor as a replacement for a concrete screed and can be used to upgrade floors acoustically, to improve thermal insulation properties of the structure (?), or as a surface covering for UFH.

The elements are laid as a floating floor and are glued and screwed together to forma continuius membrane. Once set the excess adhesive is removed and screw heads filled. A variety of surface finishes, paint, tiles, lino and vinyl coverings can be applied (but elsewhere I have see a warning that only engineered wood flooring can be used, not 'solid' wood).

Reply to
Andrew

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.