I'm slowly (given the amount of adhesive to mix!) tiling the floor of
our hall and continuing into the downstairs bog. At present, the bog
( a single storey part of the ground floor) has no heating and gets a
bit cold / damp, so I'm thinking of slapping some electric U/F heating
(probably the Screwfix mat) under the tiles (can't raise the floor
enough to accommodate wet U/F). It's only a small area so, once I
upgrade the insulation, I'm hoping it will at least keep the chill off
in winter.

Two questions:

First, has anyone had good or bad experience with the Screwfix heating
mats? They seem competitive on price and I'm assuming that a run of
resistance cable is a run of resistance cable...but you never know (!)

Second, the options seem to be to press the mat into flexible tile
adhesive or to stick it to the floor and cover in self-levelling
compound. I'm inclined toward the former (never yet managed to get a
level finish from self-levelling compound!), but perhaps someone out
there knows the pros and cons of these approaches....

Thanks people...

GMM wrote:
I'm slowly (given the amount of adhesive to mix!) tiling the floor of
our hall and continuing into the downstairs bog. At present, the bog
( a single storey part of the ground floor) has no heating and gets a
bit cold / damp, so I'm thinking of slapping some electric U/F heating
(probably the Screwfix mat) under the tiles (can't raise the floor
enough to accommodate wet U/F). It's only a small area so, once I
upgrade the insulation, I'm hoping it will at least keep the chill off
in winter.

Two questions:

First, has anyone had good or bad experience with the Screwfix heating
mats? They seem competitive on price and I'm assuming that a run of
resistance cable is a run of resistance cable...but you never know (!)

Second, the options seem to be to press the mat into flexible tile
adhesive or to stick it to the floor and cover in self-levelling
compound. I'm inclined toward the former (never yet managed to get a
level finish from self-levelling compound!), but perhaps someone out
there knows the pros and cons of these approaches....

Thanks people...

From a heat transfer POV the nearer the surface it is the better it
will be efficiency wise..that being a function of the conductivity to
where you want it to the conductivity to the cold hard ground ;-)

If you are happy to level up with cement, why not simply lay a leter of
cement and teh mat on top, and thenlay another layer and tile onto that.

I'm slowly (given the amount of adhesive to mix!) tiling the floor of
our hall and continuing into the downstairs bog. At present, the bog
( a single storey part of the ground floor) has no heating and gets a
bit cold / damp, so I'm thinking of slapping some electric U/F heating
(probably the Screwfix mat) under the tiles (can't raise the floor
enough to accommodate wet U/F).

What type of floor is it - wood or concrete ? Ours is concrete, and we
didn't use any insulation, which we may(?) regret later, but we didn't
want to raise the floor if we could help it :-}

I got a little paranoid about ours, as I didn't want to have any under
fittings, but if anything, I underestimated the size of mat i'd need.
My dad did the bathroom, and he dropped a minor (luckily correctable)
bollock by locating the sensor too far away initially - it's now
closer, but probably not optimally located.

Our stat is set to 23degC but most is around 26C with one specific
spot getting closer to 29C, and the mat was laid direct in tile
adhesive.

First, has anyone had good or bad experience with the Screwfix heating
mats? They seem competitive on price and I'm assuming that a run of
resistance cable is a run of resistance cable...but you never know (!)

We almost bought our mat from screwfix, but ended up getting it at
tlc-direct due to needing some kit screwfix didn't sell.

As far as I can tell, they're pretty much identical, we got these:

http://www.tlc-direct.co.uk/Products/BNEHM26.html
http://www.tlc-direct.co.uk/Products/BNF16C.html

The programmable switch looks complicated at first, but it's
surprisingly easy to set up, and comes with a good preset programme
that might only need slight tweaking (we needed to add heating for an
extra couple of days as my wife is part time)

Second, the options seem to be to press the mat into flexible tile
adhesive or to stick it to the floor and cover in self-levelling
compound. I'm inclined toward the former (never yet managed to get a
level finish from self-levelling compound!), but perhaps someone out
there knows the pros and cons of these approaches....

The first thing i'd do is measure up the floor area properly - mine's
in now so it's too late, but hopefully you can avoid my mistake and
not get cold spots in front of the basin and where your feet go when
you're on the bog :-}

Thanks chaps. I'm in pretty much the same situation as you were
Colin: A concrete floor and a fairly low ceiling, with the level
running right through from the adjacent hallway in the same tiles, so
I'll have to forego insulation in favour of not banging me head on the
lights...

The TLC mats look to be pretty much the same as the Screwfix ones, but
they seem bit cheaper (possibly worth the inconvenience of taking a
week off to guess when the delivery might turn up).

I think the point about planning is well made - also, since the room
is empty of fittings right now, a good plan of where things might go
into the floor (eg screws holding the bog down) might be an idea (!)

I'm not entirely convinced that these things will ever do any more
than stop the room/pipes etc from freezing, but that would be a start.

It seems the simple way is to lay it in adhesive, although the data
sheet from Screwfix says it should be the flexible sort, which will be
fun when all the tiles slump!

GMM wrote:
Thanks chaps. I'm in pretty much the same situation as you were
Colin: A concrete floor and a fairly low ceiling, with the level
running right through from the adjacent hallway in the same tiles, so
I'll have to forego insulation in favour of not banging me head on the
lights...


Or dig down deeper. However even without insulation, you wil get
reasonable efficiency. You will end up with a warm hemisphere of soil
under the floor..and a HUGE time constant since you will be as much
heating a few tonnes of soil as the room.

This makes it even MORE important to get it as close to the room surface
as possible.


The TLC mats look to be pretty much the same as the Screwfix ones, but
they seem bit cheaper (possibly worth the inconvenience of taking a
week off to guess when the delivery might turn up).

I think the point about planning is well made - also, since the room
is empty of fittings right now, a good plan of where things might go
into the floor (eg screws holding the bog down) might be an idea (!)


Yes. its not a good idea, it's bloody essential., Although I don't screw
bogs down these days. Thanks to Uk.d-i-y I use a load of silicone to
glue them. Seems to work better than screws!

I'm not entirely convinced that these things will ever do any more
than stop the room/pipes etc from freezing, but that would be a start.

If you pump in about 100W/sq meter, and the room is reaosonably well
insulated, it wll do a lot more than that.

It seems the simple way is to lay it in adhesive, although the data
sheet from Screwfix says it should be the flexible sort, which will be
fun when all the tiles slump!


Well lay the mat in flexible, and use rapid set for the tiles that go on
top.

On 26 Jun, 10:42, The Natural Philosopher wrote:

Or dig down deeper. However even without insulation, you wil get
reasonable efficiency. You will end up with a warm hemisphere of soil
under the floor..and a HUGE time constant since you will be as much
heating a few tonnes of soil as the room.

This makes it even MORE important to get it as close to the room surface
as possible.

I can't really dig it out - The solid floor is already there so it
would make a much bigger job to do much about the levels. I have a
feeling that I'll have a lot of happy worms a foot under the bog in
winter(!)



Yes. its not a good idea, it's bloody essential., Although I don't screw
bogs down these days. Thanks to Uk.d-i-y I use a load of silicone to
glue them. Seems to work better than screws!

Indeed, it might be an opportunity to try the silicone approach,
although I think I'll allow for the possibility of screws, just in
case it goes pear-shaped...

I'm not entirely convinced that these things will ever do any more
than stop the room/pipes etc from freezing, but that would be a start.

If you pump in about 100W/sq meter, and the room is reaosonably well
insulated, it wll do a lot more than that.

If it keeps the room above freezing, it will be a move forward, though
I have a feeling I'll need to attend to the walls and ceiling (single
storey, flat roof, 3 outside walls) to make it cosy in any sense!

It seems the simple way is to lay it in adhesive, although the data
sheet from Screwfix says it should be the flexible sort, which will be
fun when all the tiles slump!

Well lay the mat in flexible, and use rapid set for the tiles that go on
top.

I had thought of that, although I was wondering whether they specify
flexible so that it 'gives' rather than cracks as the element heats
and cools.

On Jun 26, 7:42*am, The Natural Philosopher wrote:
.

If you pump in about 100W/sq meter, and the room is reasonably well
insulated, it will do a lot more than that.

Interesting number. Seeing that our house is all-electric.

Just comparing ....... our 10 foot square (approximately 9 sq. metres)
fairly windy corner of house bedroom in reasonably well insulated
(1970s wood frame construction in a slightly colder than UK climate)
has a 1500 watt electric baseboard heater.
That's about 167 watts per sq. metre.

Small (no more than 6 sq. metres) bathroom in centre of house (no
outside walls or windows) has 500 watt baseboard which during much of
the year doesn't cut in at all when the six 40 watt bulbs above the
vanity are on!
So that's about 500/6 = 84 watts per sq. metre. At (6 x 40)/6 = 40
watts per sq. metre.

One argument is that the warmth being near the feet and then rising,
in floor heating is more 'effective' (don't go near the discussion of
'more efficient'!) from comfort viewpoint?

Also that in-floor is 'slower to respond' (which may be true if one
measures the ambient room temp.?).

Any thoughts on these comparisons?

terry wrote:
On Jun 26, 7:42 am, The Natural Philosopher wrote:
.
If you pump in about 100W/sq meter, and the room is reasonably well
insulated, it will do a lot more than that.

Interesting number. Seeing that our house is all-electric.

Just comparing ....... our 10 foot square (approximately 9 sq. metres)
fairly windy corner of house bedroom in reasonably well insulated
(1970s wood frame construction in a slightly colder than UK climate)
has a 1500 watt electric baseboard heater.
That's about 167 watts per sq. metre.

Small (no more than 6 sq. metres) bathroom in centre of house (no
outside walls or windows) has 500 watt baseboard which during much of
the year doesn't cut in at all when the six 40 watt bulbs above the
vanity are on!
So that's about 500/6 = 84 watts per sq. metre. At (6 x 40)/6 = 40
watts per sq. metre.

One argument is that the warmth being near the feet and then rising,
in floor heating is more 'effective' (don't go near the discussion of
'more efficient'!) from comfort viewpoint?


Oh definitely. Subjectively you can run at air temps about 2C cooler
than when you have a cold floor and rads.

Also that in-floor is 'slower to respond' (which may be true if one
measures the ambient room temp.?).


Something like a 4 day time constant here..


Any thoughts on these comparisons?