I am currently installing my kitchen. It is a Edwardian terrace (i.e. looks
Victorian). Unusually, the floor construction is suspended wooden on the
same level as the principal rooms. This is bad, because I want a slate
floor, which (to my mind) implies some sort of heating to take the edge off
the cold floor. (Space heating by radiators).
So, what is the minimum thickness I could make a slate floor complete with
underfloor heating, so I don't get too much of a step up from the back room?
The floorboards are currently layed with hardboard. It took me ten minutes
to remove a square 25cm by 25cm, it is so well affixed. I don't fancy
removing any more of it.
Alternatively, should I bite the bullet, go for a substantial step up and
install wet underfloor and insulation to replace the radiators?
We've got exactly the same arrangement - don't know whether the suspended
wooden floor was put in when the house was renovated about 16 years ago, but
it's the same level as rest of house. Come to think of it, some of the
neighbours might have a step down to the kitchen. I'll have a look next
time I',m round there.
Anyway, previous occupant of the house had ceramic tiles put in - think
they're also laid on top of hardboard and then floorboards.
Problem is that they have cracked right across the room in a couple of
places, due to slight deflection of the underlying floor, I think.
Therefore if I was replacing the floor (and we'd thought about slate) then
I'd want to take the lot up and stick some particularly meaty, flat external
WBP ply down, fix down firmly and then lay on top of that. I'd also want to
make damned sure that the ventilation was chipper, and the joists & flooring
treated first - if you get dry rot in that lot then you're buggered as you
can't get access to sort it out.
Don't know about UFH. Our floor isn't that cold - the really cold ones are
solid concrete floors, IMHO.
Of course you could bit the bullet & replace with a well insulated insulated
concrete floor, and the whole wet UFH enchilada. Don't know whether it's
feasible to do that and leave a 1ft (covered) channel all the way around for
routing pipework, cables and to maintain ventilation?
email me at
richard at olifant d-ot co do-t uk
Sounds like too much work to dig up the old stuff, although the ply on top
might be good. The kitchen units are already going in. I can't live without
a kitchen any longer and only have a couple of weekends free to fit it. The
floor will probably be done in 3 or 4 month's time. I can allow height now
when adjusting the units, appliances, and worksurface height if I know how
thick the floor will be. I won't be tiling under the units.
So, in terms of height, we have:
4mm hardboard (can't be bothered to remove).
6mm WBP plywood
3mm heat resistant compound
3mm Underfloor heating
4mm Flexible floor tile adhesive
Giving a total of 30mm. That's going to be one annoying step, unfortunately.
I've no idea what heat resistant compound is, but I'm told I need it. No
idea how thick it is really.
Sent: Monday, August 11, 2003 4:27 PM
Subject: Re: Electric underfloor heating
Just done this to my Kitchen. Wooden floor (but with access underneath
through cellar) followed by tile backer board - 10mm thick - and on top of
this Wickes under floor heater 400W with slate tiles on top, about 10mm.
The tile backer board is really to stop the heat going through the floor
boards and you don't need the heating compound with this. Can't remember
where from but I can find out if you want to email me at rokella at eurobell
dot co dot uk.
If I was to do it again I'd maybe get the 800W version because they take a
long time to heat up although hold the heat for quite a long time
afterwards. Either that or leave the floor on constantly as it is fairly
cheap apparently - obviously it's been off since installation and testing in
As Andy said, I wonder now if I really need it as we wear slippers about the
place, but what the hell it's a neat feature that I point out to all who
enter. BTW don't rely on this to heat the room - it's only to take the edge
off the tiles.
(I don't check this ng regularly so you may not get a quick response if
About 30 miles?
You can make a screed floor as thick as you want. Ideal is about 10-12"
from teh soil, with hardcore, sansd blinding, screed, Damp proof
membrane, insulation, then pipes-in-screed. Or wires I guess.
Sounds interesting, I'll give it a look. It would have to be really thin,
though. I forgot about the windows in the kitchen. In true Edwardian style,
they go down quite low. The standard worktop height is already above the
architrave and, in fact, will be just touching the sash beading. I'm happy
to raise the floor a little if the integrated appliances can still fit under
the surface, though. The floor won't be going under there, so I can make a
little down ramp.
It looks like it would be too thick. You need 15mm pipe, 18mm plywood and
what looks like about another 15mm of insulation below the pipe. I don't
think I'd get the integrated appliances in under that. I'll measure it up,
though. I can't (i.e. won't) lift the floorboards or get access underneath.
Any idea of how much a suitable system would cost if it does fit? The room
is a galley, 5m by 1.4m, widening for the last metre to 2.6m (I could live
with just heating the central strip, though). What bits would I need,
I'm also worried about how wet heating would work in practice. I only really
intend to use the electric underfloor as a "boost" setting about half an
hour before intending to cook. Would a wet system have a longer response
time, especially with 18mm of ply insulating the tiles from the pipes?
I think I may have found the wrong system on their website. I'm not laying
laminate, but slate tiling. What material would be required between the
overlay panels and the tile adhesive?
If I can use 6mm WPB ply, then I get:
0mm plastic membrane
18mm overlay panel
6mm WBP ply
4mm flexible floor tile adhesive
Giving 42mm thickness, which is 12mm more than electric, but may just be
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