Help!: Tiling over concrete/suspended floor joint

[danblez]

Hi all,

Great forum!

I am after some advice as I am having an extension built and the new room will be half suspended wooden floor and concrete floor and my builder is concerned about there being movement which could cause the tiles to crack.

Obviously the wooden floor will be made sound and any springiness in it removed before tiling but are there any other tips which would help to make a stable floor?

Having done some reaserach I think maybe 10mm tiles backer boards could help to make a stable joint and as I as going to be putting insualtion down anyway this seems like a sensible way forward. The cost of this is rather a lot though and I have 65 square metres to do, but I want the job doing properley that will last.

Oh one last thing to note is I will be having 3 zones of electric floor heating also.

Any help much appreciated.

Cheers
Dan

[Gall.B]

Hi and welcome to the forum, your right it is great and a fantastic resource,

You are making a lot of the right noises, you will defo need expansion joints 1 where the suspended and concrete floor meets, and within 4 metres at regular interval there after.

What type of tile is it, how flat/level is the floor currently.

Do you have a Tiler? He may be able to get you good discount before you get materials.

[danblez]

Wow superfast response thanks. The tiles are 600 by 300 square edge porcelain tiles, recommended 3mm gap

When you say an expansion joint what do you mean? Obviously I understand the purpose of one I am just wondering how this works practically? Is it a joint between tiles which has silicone in it or more to it than that?

The floor at present is very flat, new concrete just gone down and the original suspended floor is in good condition.

The builders son is a tiler but I don’t know him or the quality of his work and wanted to make sure it was done 100% right so there are no tears afterwards.

Thanks again for the superfast response!

[Gall.B]

First thing to check with your tile is how flat they are depending on quality some can be bowed ie not completly flat just takes a slight deviation to give you problems & depending on your pattern Broken bond (brick effect) or normal bond try laying some out on a flat surface.

You can buy expansion joints with diffrent finishes, check schluter systems site and they must be installe correctly. or a silicon joint to match grout colour would suffice.

You need a good quality flexiable addy and flexiable grout prefreably with porcel bond in it

Are you installing U.F.H. as it effects the overall prep of the floor, make sure PVA is not used at any stage

Make sure you get a written guarantee from The tiler and detailed program of work from whoever you use. as you say it aint cheap!
Ask him for examples of his work?

There is also good threads in the directory giving you good info and advice on products and answers to your questions.

Good luck with it

[danblez]

Brilliant thanks, I will have a wander through the rest of the site.

So the expansion joint is an absolute must is it? I will start by discussing this with him which should give me a good idea of his knowledge.

[Rich]

Good advice above, an expansion joint between the two substrates is a must Im afraid, I think that you would be asking for problems if you went ahead without installing then, and as has been said above you will need to install one every 5m or so of tiling. A silicone joint is much easier to hide in a field of tiles as you can match the grout colour but this will need replacing every few years or so where as a pre formed expansion joint stands out more but should last the life of the floor.

With regards to adhesive, if you are supplying the materials, I would have a look at Mapei's range. Do you have a tile giant near you? If so they should be able to get you everything you need regarding adhesive/grout/silicone/primer. Porcel bond is not a chemical, it is a made up element that BAL put on their products to make it clear that it is suitable for porcelain and to sound really scientific, you will not find this in the Mapei range, you just need to tell the people that you buy the adhesive from, the type of tiles, the substrate and the area. They should be able to sort it all out for you.

[danblez]

Loving this forum thanks Rich, I think i will have to buy a pen or two

I think I will leave the purchasing of the materials to the tiler to be honest, the more I look into this the more complicated it seems to become. Like everything in life though when doing a job properley it is never that straight forward.

With regards to primer, is this for priming the concrete floor before laying the tilebacker boards? What type of primer is used? I presume you just screw down the boards to the suspended floor with stainless screws?

Where should the expansion joint be exactly? Should it sit precisley over where the two different floors meet? Are the tilebacker boards laid accross this joint or do you need to lay them in the same way underneath the tiles ie. along the join?