Floor Tiles on to Plywood.

[wilmslowwhite]

I'm a enthusiastic DIYer. I've knocked through a cupboard to make an ensuite bigger (its now about 3m2); removed a cast iron bath; put in new shower; extra basin, moved wc and tiled the walls with large tiles (1000mm x 333mm and 592mm x 333mm). Done everything myself apart from plastering one wall and I'm really pleased with the job so far. Had some great advice from the forum along the way.

I'm in to the last part of the job, tiling the floor.

The floors were tongue and groove boards. After I had laid new pipework most of the boards were ok so I put them back down, screwing wherever I could. I know you guys wouldn't have done what I did next but I was concerned about the height of the floor and was partly going from a DIY book - I laid down 6mm ply. I nailed it down every 100mm and then I've tanked the room with BASF Lastogum.

The floor seems ok to me, their is a small area where there is a bit of movement when you stand and transfer weight from side to side but I don't think its so major.

I could do with your advise on the following:

1. For the floor tiles I was going to lay down a thick bed of adhesive (12mm), thinking that this will give a bit more support/firmness for the tiles - will this help or has anyone got any better ideas?

2. Any advice on the best adhesive for this job? I used a Bal Flexible Single part for the large tiles and was going to use this again for the floor.

3. Will it make any difference if I use larger or smaller spacing for the grout?

4. Any other tips for making the job stronger/firmer?

All advice will be greatly appreciated.

Thanks fellows.

 

[martin1c]

First of all you probably already know that 6mm ply is no good from reading other posts. Also, it should be screwed done and not nailed. Most suggestions on here will tell you to pull it all up and start again but if you are determined to try and make the best of a bad situation there is one option. You could cut a channel in the ceiling below to expose the joists and put noggins between all of the joists to strengthen the floor. Obviously you will have to have the ceiling skimmed again unless your DIY skills are good.

 

[Brian the Tile]

if you want the job to be ok for tiling please take it up and start again you know its wrong so why take the risk as above the ply should have been screwed not nailed but you might aswell have put cardboard down,dont take the risk of it coming up if its worth doing its worth doing proper first time

 

[Mike Mike]

I'm confused. You said you put down 6mm ply because you didn't want the floor too high yet you are now planning to put down a 12mm bed of adhesive to strengthen the floor? That's crazy. Apart from the very high cost of building up an adhesive bed that thick, it will be extremely difficult to get a flat and level floor with a bed that thick.

Martin and Brian are spot on.

Your best bet is to write off the tanking kit, take up the ply, put noggins in the floor to stop the deflection, then re-board (glue and screw) with No More Ply (6mm), tank the floor again and then tile onto that with a sensible adhesive bed thickness (4mm from a 10mm trowel). You will achieve your lower floor height that you originally wanted, will avoid future problems, and will probably save yourself money (trust me, at 12mm thick you'll be getting through a LOT of adhesive).

There is a Scandinavian alternative approach (but assumes your floor has no deflection, assumes your joists are probably thicker and closer together than they actually are in your English house i.e. every 300mm) and that is to staple steel reinforcing mesh to the floor, then pour self levelling compound at a minimum thickness of 12mm, then tile onto that. The added weight of doing that would, like your tile adhesive suggestion, be completely unnecessary and counter-productive when cement based tile backer boards exist for a tenner each, or thereabouts.

 

[Perry]

The ply is to thin it's delaminating putting any thickness of adhesive won't solve the problem