Thoughts on this

[Gazzer]

A while back I went to quote for a floor. The substrate was 18mm ply on joists. Very solid and no problem except they wanted backerboard, UFH and Travertine or limestone...maybe polished marble. The first thing I noticed was 4 doors were too low and You wouldnt be able to get the depth needed.
Adjusting the doors is a no go as one door is a folding door , about 2 metres wide. The others are UPVC and to adjust would be major work.
They left it at that . I now have an email stating that a "builder " will remove the ply and cut it into the joists, thereby giving an extra 18mm.
This will still be overboarded with backerboards but I am not too keen on the idea. In theory it may be fine but until I see how well this "builder" is then I dont feel I can give a definite answer.
How would you play it ?

 

[Dougs Third Go]

but how is the ply going to be supported? with battens attached to joists? if so it'll be seriously under strength.

 

[Gazzer]

Exactly Doug, my thoughts too but as you know " Our builder says it will be fine" I think it would reduce overall strength.

 

[Ian]

I suppose in theory if extra noggins were added 18mm below finished joist height, with battens, to support the ply, it may work. I suppose you would have to see what the deflection was like after this was done. As Doug says, it would surely be under strength as there would be continuous breaks in the substrate, essentially all this would be doing would be in filling the joists.

 

[Gazzer]

Well this is the problem. It could be done , if they take a belt and braces approach but will they ? I wont know until its done and even then I still dont like the sound of it.......all those straight joints every 450mm etc

 

[Ian]

Maybe achievable on a small floor, this sounds like quite a big area. What's the m2?

 

[Gazzer]

Its about 21m2 in total.

 

[Mr T]

Couldnt you plain the folding door to the correct depth? and then raise the bottom section somehow? Or am I way off the mark lol

 

[BoldreChris]

It could be done by reducing the joists themselves by 18mm - b1tch of a job but that would leave you with a continuous ply base to tile onto.

 

[Gazzer]

Couldnt you plain the folding door to the correct depth? and then raise the bottom section somehow? Or am I way off the mark lol

Miles off the mark !

 

[Ian]

Its about 21m2 in total.

That's way too big an area I reckon, it'll be interesting too see if it works.

 

[Dougs Third Go]

It could be done by reducing the joists themselves by 18mm - b1tch of a job but that would leave you with a continuous ply base to tile onto.

but then you'd be weakening the joists.

 

[ian158]

I take it its downstairs given the UPVC doors..the bifold will be easy enough to plain, but UPVC, be easier to move them up if the brick work can be cut above door,,less work in making good than taking floor up, cutting each joist ! nightmare job that would be, even with a festoon plunge saw.

 

[Ajax123]

I don't think weakening the floor would be too much of a concern in this instance. If they were taking lumps off the joists then yes but just in filling is not really much of a worry for me.

of greater concern would be the level of movement in the floor. Bear in mind that the joists will move at a different rate to the ply and if it is cut in really tightly it will try to belly when heated.

With trav this one sounds fraud with danger.

 

[Gazzer]

Bifold doors are four doors made from UPVC...about 1800mm