Underfloor Heating

typeractive

I'm still looking into this underfloor heating. From my understanding the install would be like this:

joists
floorboards
8mm plyboard (probably marine ply)
10mm insulation board
heat mat
grout (flexible)
tiles.

Though looking at the warmup video demo on youtube, they don't specify the need for the insulation boards, but they do recommend 18mm ply.

Does anyone have any recommendations here?

Has anyone laid their heatmats directly onto plyboard? I'm sure it will work out cheaper, and the real benefit of this would mean I can work on other stuff in the bathroom standing on top of the ply carefully, rather than standing on top of any expensive insulation boards which I'm sure would crease / snag / dent.

Opinions welcomed!

andyhop

Incorrect information there which would probably lead to failure and definatly a HUGE step into the room

Best way would be to remove existing floor back to joists

22/25mm marine ply screwed directly to joists, extra timbers at all edges

Insulation - I find that a solid type board 50mm+ under the plywood between floor joists works best, fill edges with expanding foam

Lay heat mat and cover with Latex SLC (3-4mm deep)

Use flexible adhesive or latex additiive, something like Mapei Keraquick and Latex plus

Grout- Mapei ultracolour is fine

Turning on - Start low and work your way up, usually say to customers a few degrees a week to max. To be left on constant until max temp is achieved

typeractive

andyhop wrote: »

Incorrect information there which would probably lead to failure and definatly a HUGE step into the room

Best way would be to remove existing floor back to joists

22/25mm marine ply screwed directly to joists, extra timbers at all edges

Insulation - I find that a solid type board 50mm+ under the plywood between floor joists works best, fill edges with expanding foam

Lay heat mat and cover with Latex SLC (3-4mm deep)

Use flexible adhesive or latex additiive, something like Mapei Keraquick and Latex plus

Grout- Mapei ultracolour is fine

Turning on - Start low and work your way up, usually say to customers a few degrees a week to max. To be left on constant until max temp is achieved

Thanks andy. Replacing the floorbaords was also another route we were thinking of! Can I ask why it would lead to failure though? I know about the massive step that I would need to account for. I was thinking I'd just make a nice wooden step to level it off? (albeit, a bit of a big one - say 30mm!)

I'm planning to bung in a load of kingspan style insulation between the joists anyway (as the room beneath is the kitchen). The kitchen ceiling is exposed and like spaghetti junction with loads of cables and pipes running to and from it!

The main thing is - you have helped to confirm my thoughts a bit - basically I do not *NEED* to lay the mat onto the special insulation boards. I can just put it onto a nice clean ply finish.

For some reason I'm just a bit nervous of taking the old floorboards out? Maybe it's because there is a stud wall running around on top of them? Or maybe I'm scared if I can't get it all correctly level...though I suppose laying the tiles could be an area of forgiveness.

What is "Latex SLC"

The good thing if I do decide to replace the floorboards, is that it might enable the plumber to sort out some of his pipework as I'm not too happy with it to be honest. It looks messy.

Do you work in this industry andy?
Cheers again for teh advice - it's appreciated!
:j:beer:

andyhop

Hi

6-9mm plywood is too thin

British Standards quote 15mm minimum for floor overboarding prior to tiling. From experience a minimum of 12mm is required with the existing floor being screwed down tight then plywood screwed every 150mm

Latex SLC - Self levelling compound. Best for timber floors is Mapei Fibreplan with its fibre reinforcing but £30 a bag. Best value for money is Weber Floorflex at around £15 per bag

Some UFH mats require cement /insulation board if the heat output is more than 100w per Sqm. Unless you want your house to go up in flames!

If there are stud walls set intop of the floors then this can be tricky, either remove nails/screws from inside the stud wall and take the floor up to the nearest joist or cut flush with wall then brace with 5x2 timber

Yes this is what i do for a living unfortunatly

typeractive wrote: »

Thanks andy. Replacing the floorbaords was also another route we were thinking of! Can I ask why it would lead to failure though? I know about the massive step that I would need to account for. I was thinking I'd just make a nice wooden step to level it off? (albeit, a bit of a big one - say 30mm!)

I'm planning to bung in a load of kingspan style insulation between the joists anyway (as the room beneath is the kitchen). The kitchen ceiling is exposed and like spaghetti junction with loads of cables and pipes running to and from it!

The main thing is - you have helped to confirm my thoughts a bit - basically I do not *NEED* to lay the mat onto the special insulation boards. I can just put it onto a nice clean ply finish.

For some reason I'm just a bit nervous of taking the old floorboards out? Maybe it's because there is a stud wall running around on top of them? Or maybe I'm scared if I can't get it all correctly level...though I suppose laying the tiles could be an area of forgiveness.

What is "Latex SLC"

The good thing if I do decide to replace the floorboards, is that it might enable the plumber to sort out some of his pipework as I'm not too happy with it to be honest. It looks messy.

Do you work in this industry andy?
Cheers again for teh advice - it's appreciated!
:j:beer:

typeractive

andyhop wrote: »

Hi

6-9mm plywood is too thin

British Standards quote 15mm minimum for floor overboarding prior to tiling. From experience a minimum of 12mm is required with the existing floor being screwed down tight then plywood screwed every 150mm

Latex SLC - Self levelling compound. Best for timber floors is Mapei Fibreplan with its fibre reinforcing but £30 a bag. Best value for money is Weber Floorflex at around £15 per bag

Some UFH mats require cement /insulation board if the heat output is more than 100w per Sqm. Unless you want your house to go up in flames!

If there are stud walls set intop of the floors then this can be tricky, either remove nails/screws from inside the stud wall and take the floor up to the nearest joist or cut flush with wall then brace with 5x2 timber

Yes this is what i do for a living unfortunatly

Right. Well now I can't decide if I want to overboard or rip the boards up and lay on the joists! This renovation stuff is never easy!

Forgive my ignorance, I can't see the beneift of laying relatively thick ply onto floorboards - I can see the point if I do replace the existing floorboards, but would have hoped I could get away with just overboarding. hmmm

Here is a diagram of my bathroom:


The shower and bath aren't that narrot - they should be x 800mm! lol

So the total square m of my room is, 5.6m, though I only aim to lay the mat on the walkable area, which I think will be roughly 3m sq.

That would mean I will probably buy this mat (2.5msq) here which is 100w per sq mtr as I won't fill to every spare area. (do you have any opinions on this mat perhaps? price etc).

I certainly don't want the house to go up in flames!!

I've been speaking to my mate, and he says the jobs he's worked on he has seen joiners putting LOADS of screws into the ply - which mirrors what you suggest also.

If I wasn't putting down UFH (such as in my en suite) what is the minimum size ply I can overboard with and tile onto?

I admitt it is tempting to overboard. The walls are plasterboarded, with insulation inside. I think I would have to cut flush right up to the walls, and add timber to the joists as you suggest. hmmm

diable

I took out my old boards and replaced them with ply to get a nice level floor. I also had the aluminium foil placed underneath which is meant to help reflect the heat upwards from the under floor heating and not help heat the downstairs ceiling.

decorative-concrete

It sounds so interesting!

diable

decorative-concrete wrote: »

It sounds so interesting!

It'll be a celebration in progress, then the artistic concrete goes in........

typeractive

diable wrote: »

It'll be a celebration in progress

Diable, I will be there with :bdaycake: & :beer: for us.

...then the artistic concrete goes in........

Artistic concrete you say? Well, indeed art is in fact all around us within our daily lives...apparently even the most boring and mundane materials such as concrete can be made to look decorative.

Rachel Whiteread is of course well renowned for such skill...perhaps we're blessed with her presence on the forum?...now that actually would be interesting. I really hope we don't just have boring concrete though...

diable

typeractive wrote: »

Diable, I will be there with :bdaycake: & :beer: for us.

Artistic concrete you say? Well, indeed art is in fact all around us within our daily lives...apparently even the most boring and mundane materials such as concrete can be made to look decorative.

Rachel Whiteread is of course well renowned for such skill...perhaps we're blessed with her presence on the forum?...now that actually would be interesting. I really hope we don't just have boring concrete though...

Ahh someone artistic with a creative and open mind ;o)))