Cracked Tiles

[pandl73]

I have a marble tiled floor which is cracking along the lines of the plywood underneath. Yes the ply has been laid with the joints in line. Hindsight is wonderful. It has been down only 4 months It is a suspended timber floor, with 12mm plywood sheets (I now know it probably should have been 18mm) overlaid with 15mm marble tiles. After reading other posts, I realise the cause, but can I make good the floor as I simply can't afford to rip it up and start again?

Will I always have flex and movement in this floor, or will it after time settle. I am contemplating waiting six months or so then get the cracks filled and get a pro to skim off 1mm off the floor polish and seal to restore it as new, or will the same happen again? The builder is also proposing to construct a wall under the joists (they span 4m) to support them midway to reduce any flexing, or is this a waste of time?

 

[1john]

With that weight the floor should have been 25mm ply, If I were doing it there would have been noggins everywhere, aspecially where boards meet and the joins would have definatly been staggered. I dont feel that it will settle in time.

What size are the joists and what centers are they on?

I have some ideas on beefing up the floor if you have access from below, they would be time consuming but if you want I can post my ideas, I dont think it will cure it but I think it will add alot of strength which you are currently lacking.

 

[Richard C]

I have a marble tiled floor which is cracking along the lines of the plywood underneath. Yes the ply has been laid with the joints in line. Hindsight is wonderful. It has been down only 4 months It is a suspended timber floor, with 12mm plywood sheets

Is that an over board or just 12mm ply on he joists? Is this a bathroom, itchen or what?

I now know it probably should have been 18mm

If a new ply floor over joists, 18mm WBP is the absolute minimum, sometimes 22mm or even 25mm is required depending on joist size/pitch/span & if it's a light or heavy load/traffic area.

overlaid with 15mm marble tiles.

Heavy tiles, what size are they?

After reading other posts, I realise the cause, but can I make good the floor as I simply can't afford to rip it up and start again? Will I always have flex and movement in this floor,

Almost certainly if it’s only 12mm ply.

or will it after time settle.

Settle where? if the floor basically has too much flex, no amount of "settling" will make any difference, it will still fail.

I am contemplating waiting six months or so then get the cracks filled and get a pro to skim off 1mm off the floor polish and seal to restore it as new, or will the same happen again?

Probably; you may be just throwing good money after bad!

The builder is also proposing to construct a wall under the joists (they span 4m) to support them midway to reduce any flexing, or is this a waste of time?

Well the 4m span is your problem; what size pitch are the joists? I’m intrigued as to how your "builder" is going to construct a wall under the joists , is this a suspended ground floor? is he going to brick off a beam? or is he going to partition your lounge

4m is a big span, noggins wont do much for the overall floor rigidity but sistering the existing joists will help; is it your builders fault your in this predicament?