Expansion Joints - TilersForums.co.uk | Tile Forums

mick7 · 11-01-2008

Hi All

You are probably all in bed, I'm still up trying to sort out the bits and pieces that need doing in a new extension.

As per previous thread I have a 3.5 deep new extension( 6 week old screed) which leads out from a 3.5 deep existing build ( concrete floor). Where the back of the old house was knocked out to build the new extension there are 2 pillars ( supports) .

There is no expansion joint showing in the new floor where the new meets the old and none has been specified in the plans?

How do I run a 7m length of 60 x 60 porcelain tiles through this area ???

Any ideas please.

**grumpygrouter** · 11-01-2008

Hi Mick, without seeing your floor I am guessing a bit but can you use the join between the two screeds as your datum and tile out from either side of that? If not check out the Schluter site, they do an excellent range of joints that look the biz and wouldn't be out of place in a domestic environment.

Possibly, as both surfaces are concrete, once they have settled you may not even need an expansion joint. In fact you may well be ok to use Ditra matting - this is designed for this sort of thing - see attachment

Grumpy

mick7 · 11-01-2008

Thanks for reply.
I have had a look as Schulter, just did'nt realise I should have an expansion joint. Really woriied about the look in the middle of a new floor. Definitely cant afford to do 50 sq metres with Ditra.
What I cant understand is that none of the tilers that quoted mentioned an expansion joint. Dont really know what to do. Do I let one of them tile it and chance it.

**grumpygrouter** · 11-01-2008

Mick, a 7m run of tiles on a floor doesn't really need an expansion joint. BS states they should run every 8 -10 m on a large floor or if there are different substrates to bridge. The only reason I mentioned the schluter is that you have an old concrete slab abutted against a new one. There may still be some movement in the new one for sometime and if you bridge the join with a tile it i may crack. If you use a good flexi adhesive it may help but I am not sure as I don't have enough experience yet to give a difinative answer.

What I will say is if you are putting down 50m2 of porcelain tiles that in itself is not cheap and it would be a shame to have to start pulling it up to make repairs. You can get 30m rolls of Ditra for around £6.50 per mtr (£195 +vat) and if it was me, I would use it for the piece of mind.

Good luck what ever you decide.

Grumpy

mick7 · 11-01-2008

Thanks for that.

Can you tell me where I can buy Ditra at £6 per metre, I'm near London and cant get it under £10. At your price I could possibly afford it.

**grumpygrouter** · 11-01-2008

Mick, I have sent you a PM, mate.

Grumpy

**pjc** · 11-01-2008

Mick why do need Ditra ?

mick7 · 11-01-2008

I dont know whether I need ditra or not, I'm just trying to avoid a horrible joint line showing right in the middle of the floor. Its not the 7m run that worries me it is that at 3.5m the new screed joins the old floor ( all nice and level and sound at the moment1) and you experienced guys say there might be some movement that will crack out the floor.
Dont know what do do, and know one that has quoted has even mentioned it !!

**grumpygrouter** · 11-01-2008

Quote:

Originally Posted by pjc

Mick why do need Ditra ?

What are your thoughts on his question Pete?

Grumpy

**pjc** · 11-01-2008

it should be ok or you do as Grumpy suggests put a tile joint on the screed join and silicone it leave the expansion to the perimeter ie put skirting on top of the tiles

alex1963 · 11-01-2008

i've done a lot of extensions where old concrete meets new and i always run a grout joint along the concrete joint with colour marched silicon,if you do it right you can barely pick it. only problem would be if the concrete isnt tied in properly,but then it would be the builders problem!!

**Dave** · 11-01-2008

Ditra will not overcome this problem mick...it is a crack isolation membrane and vapour equalisation membrane .. It will not act as an expansion substitute...
The builders should have put an expansion point where the old meets the new..no other way around it, apart from if they had laid a complete new floor throughout...You need to determine where they join at and put an expansion joint at this point be it a profile trim or silicone joint....good luck...