Tiles may crack?

[blueman]

Can anyone help

A few questions I want to ask my builder, before we the tiles are laid

So far the builder has laid a underfloor heating system, water based, on kingspan, between a timber frame (on a solid concrete floor) - 50mm screed on top, then chipboard - I have been told by a few tilers that this could lead to the tiles cracking (due to the heat crumbling the screed and chipboard curling) - is this true? Also you should also use only plywood to lay the tiles on.


The reason why a 50mm screed was used and also the timber on the solid floor was due to the lack of height left (not enough room for 100mm kingspan 75mm of screed) - create a timber floor effect.

Would appreciate any help

[Dave]

Hello and welcome..


Ok.. Slow down.. explain how this is put down..?

[whitebeam]

Sounds like a mish mash to be honest...

[jay]

Can you run us through the floor make up not quit getting this

[blueman]

Thanks for your rapid replies.

I have a link to a diagram if I can add the URL?

The chipboard is 18mm

Screed 50mm

Water based underfloor heating on Kingspan, the underfloor heating pipes run through the wooden frame (slots have been cut, wooden frame glued to the concrete floor, 18mm chipboard screwed onto the wooden frame, 50mm screed has been added on top of the kingspan/pipes). I think the kingspan is 30-40mm.

This all rests on a solid concrete floor, ground level kitchen area.

Is 50mm enough screed? Can you lay tiles on chipboard? Can we use the underfloor heating and not crack the tiles?

Basically the builders added too much concrete when fixing the solid floor base. They didn't leave enough room for the underfloor heating, screed (75mm), insulation (100mm), board (22mm)

[suave]

welcome!

[whitebeam]

I take it it's a standard sand/cement, not suitible for laying onto a chipboard substrate..

[Ajax123]

This quite a common method . The heat will only crumble the screed if the screed is rubbish. Given what you have done though this is not important as the screed is not being us d as a screed but as a heat medium. Chip board though is a bit of a no no. Either remove it and replace it with ply or overboard it with backer boards. I am assuming there is enough timber frame under the chip board to support it and prevent deflection otherwise I'd say start again

[blueman]

Thanks for your rapid replies. To clarify:

The chipboard is 18mm

Screed 50mm

Water based underfloor heating on Kingspan, the underfloor heating pipes run through the timber frame (slots have been cut, timber frame glued to the concrete floor, 18mm chipboard screwed onto the timber frame, 50mm screed has been added on top of the kingspan/pipes).

The kingspan is 40mm.

This all rests on a solid concrete floor, ground level kitchen area.

Is 50mm enough screed?

Can you lay tiles on chipboard?

Can we use the underfloor heating and not crack the tiles?

Basically the builders added too much concrete when fixing the solid floor base. They didn't leave enough room for the underfloor heating, screed (75mm), insulation (100mm), board (22mm).

Thanks again for your replies.

[Rich]

Im not sure if I understand the make up of your floor. Whatever it is, chipboard is not suitable to tile onto under any circumstances. As has been said above, it will either need to be replaced with suitable ply and then over boarded or over boarded with a cement board. If you replace the chipboard or just over board it, the boards must be fixed down securely, any deflection in the floor will cause problems.

Is the builder doing the tiling? If so may I ask why?

[Ajax123]

The floor makeup is straight forward. Two modifications I would make though. 1 drill, plug and screw the timber battens down. If not and the glue suffers in the future you could find it warps bringing the tiles up with it which will cause problems. 2either ditch the chip board altogether in favour of ply or over board it with hardibacker or the like. 50mm screed would be incorrect if you were using it as a screed to tle onto but you are not. It is simply acting as a heat medium. In this instance the less mass yo have the faster your heating will respond and the mr efficient I will be. Am not sure there is a specific name for this floor makeup as it s neither floating nor bonded. Either way it is very common. Usually at first floor level. It is what I have in my lof conversion but I onl put 25mm screed in.

[blueman]

Thanks again for your replies.

I have spoken with the builders today and they suggest to overboard the chipboard with 6mm ply. If we go in this direction do you think we'll be able to use the underfloor heating?

Will the chipboard curl due to the heating and push the ply up?

Another option is to remove the chipboard (which is a tad tricky due to pipe work etc) and replace with 18mm or 22mm ply - again if we do this can we use the underfloor heating? Will this be a safe option?

[TMTservices]

overboard chipboard with hardibacker. As long as everything underneath chipboard has been done correctly. Avoid ply. Theres no need for it. DEFINATLEY NOT 6mm ply. DO NOT USE PLY. IMO

[blueman]

Sorry on emore question - Use 6mm hardibacker instead of ply 6mm - over the chipboard?

[blueman]

Thanks TMT Services - If we use Hardibacker then, can we then use the underfloor heating?

[TMTservices]

Im not 100% about the make up underneath the chipboard, but all I'm saying is try to leave ply out of the build. As far as I'm concerned 6mm hardi is a far better surface to tile to. Not too expensive if you look hard enough, either.

[blueman]

The main thing is we can use the underfloor heating and not run the risk of cracking the tiles (whether we use ply or hardibacker). If not then perhaps we should cut our losses and turn off the underfloor heating?

[Bathfix Bob]

I don't know whether the builder should be tiling this floor, every week on here there is another thread about problems with floor tiles laid by builders.

Make sure when they use Hardiebacker they lay it on flexible powderd tile adhesive as well as screws. Nobody would tile on 6mm plywood unless they wanted cracked tiles.

Regarding the underfloor heating and cracking tiles I don't think anyone here can give a cast iron yes or no answer without seeing it in person, maybe pics will help.

It all depends on how well everythings put together.....

[jay]

Question would you employ a plumber to build a new house ..

[andy allen]

builders build, plasterers plaster, painters paint,........and tilers TILE !!!!