Limestone over ufh and chipboard

[Rich Midge]

Opinions please gents. I've been to see a job this morning where the homeowner has seemingly been let down by a series of tilers who were supposed to do the job but now can't. The floor is newly constructed chipboard caberfloor over 6x2 joists with a wet ufh underneath. This has been pressure tested but not heated. The disappearing tilers were all happy to tile straight over using a Granfix S1! The floor does feel well constructed with no bounce, so I've advised decoupling. However, I'm still not completely convinced this is going to last so am having second thoughts on taking the job on. The limestone is 3 sizes, the biggest of which looks to be around 900 long. Would you take this on?

 

[Ajax123]

not with a bargepole personally.

 

[Rich Midge]

Turned this one down. Thanks Ajax for your reply. Was going to be a nice payday but probably not worth the sleepless nights waiting for the phone call to say it's failed.

 

[Ian]

I did a similar floor about 18 months ago, 500mm x random length upto 900mm, hardiebacker glued and screwed, then ditra glued, then tiled. A very solid installation, 60 or so m2. I'll see if I can find some pics later.

 

[Rich Midge]

I did a similar floor about 18 months ago, 500mm x random length upto 900mm, hardiebacker glued and screwed, then ditra glued, then tiled. A very solid installation, 60 or so m2. I'll see if I can find some pics later.

Yep, was trying to advise him this way. He wouldn't entertain paying for Hardie and Dural so the compromise was just to decouple. When I called to say I wouldn't be doing the job he asked would ply be ok. Don't understand why people go to the expense of ufh, limestone slabs and then want to compromise on prep and installation. The tilers who didn't show incidently were highly recommended and considerably cheaper.

 

[Old Mod]

Hey Rich,
Just been looking at Norboards website, here's their tiling spec.

Guidance as to construction of bases in respect to considerations and timber bases is given in BS 5385: Part 3: 1989. Tiling onto Caberfloor should be undertaken only in joisted / fixed floor constructions. Noggins should

be used between the joists at 300mm centres and the surface provided for tiling should be 15mm exterior grade plywood screwed to joists and noggins at 300mm centres. Existing boards can therefore be overlaid with 15mm exterior grade plywood to provide the necessary rigidity for a tiled surface. Length of fixings should be 2.5 times overall board thickness. A tile adhesive is the recommended bond material -cement/sand mortars are not recommended.

Perhaps it'll sway your client?

 

[Rich Midge]

Hey Rich,
Just been looking at Norboards website, here's their tiling spec.

Guidance as to construction of bases in respect to considerations and timber bases is given in BS 5385: Part 3: 1989. Tiling onto Caberfloor should be undertaken only in joisted / fixed floor constructions. Noggins should

be used between the joists at 300mm centres and the surface provided for tiling should be 15mm exterior grade plywood screwed to joists and noggins at 300mm centres. Existing boards can therefore be overlaid with 15mm exterior grade plywood to provide the necessary rigidity for a tiled surface. Length of fixings should be 2.5 times overall board thickness. A tile adhesive is the recommended bond material -cement/sand mortars are not recommended.

Perhaps it'll sway your client?

In fairness his floor was solid, so a plywood overlay as above ( although old school!) would probably be sufficient for porcelain or even some ceramic but would you happy laying large limestone knowing there's ufh there as well? Still happy I turned this one down.

 

[Old Mod]

In fairness his floor was solid, so a plywood overlay as above ( although old school!) would probably be sufficient for porcelain or even some ceramic but would you happy laying large limestone knowing there's ufh there as well? Still happy I turned this one down.

No def not! Would of swapped ply for Hardie all day long, that was really to show the principle that they suggest.
Their suggestion was for ceramic tiling not stone. Sorry should said what I was suggesting.
In theory the Hardie would be sufficient but I'd pushed for a decoupling mat too.

 

[Ian]

I seem to have lost/deleted most of my pics from said job, I've found one on my Twitter account from early on in the job, hardies were laid herring bone to stop any long joint runs

 

[Dave]

6 x 2 joists ... Lol...

 

[On one]

Hey Rich,
Just been looking at Norboards website, here's their tiling spec.

Guidance as to construction of bases in respect to considerations and timber bases is given in BS 5385: Part 3: 1989. Tiling onto Caberfloor should be undertaken only in joisted / fixed floor constructions. Noggins should

be used between the joists at 300mm centres and the surface provided for tiling should be 15mm exterior grade plywood screwed to joists and noggins at 300mm centres. Existing boards can therefore be overlaid with 15mm exterior grade plywood to provide the necessary rigidity for a tiled surface. Length of fixings should be 2.5 times overall board thickness. A tile adhesive is the recommended bond material -cement/sand mortars are not recommended.

Perhaps it'll sway your client?

So......Am I correct in reading that as,the joists at 300mm centres and noggins at 300mm centres?
Well that aint gonna happen!

 

[Old Mod]

So......Am I correct in reading that as,the joists at 300mm centres and noggins at 300mm centres?
Well that aint gonna happen!

I think they maybe covering themselves! Haha

 

[Rich Midge]

Noggins at 300mm centres and overlay screwed down at 300mm centres is how I read it.

 

[Rich Midge]

Still can't quite believe that others were willing to tile the floor as it stood, 6mm ply and the odd ring nail should sort it

 

[On one]

Noggins at 300mm centres and overlay screwed down at 300mm centres is how I read it.

Yeah,just reread it
but no mention of joist spacing? 600mm centres anyone!
But in effect 15mm becomes 18mm plywood due to availability,but why would you put ply down at all?