Tiling over Cracked Concrete

[BMD]

Hi,

Does anyone have any advice on tiling over cracks/joints in concrete screed. A few hairline cracks are emerging in my concrete screed and I want to know what should I do or what products should I use (e.g., membranes) to avoid these cracks appearing in the tiles after they are laid

[Alan.P]

How long has the screed been down, is there any underfloor heating and how big are the cracks.

[BMD]

about 70 days...moisture test done and its ok for tiling...there is UFH and the cracks are hairline while the joints would be 2-3 mm

[Bri]

Have the cracks appeared while the heating has been running? This is quite normal.


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[Del W]

How big is the floor.

[Phil Hobson]

Is the floor concrete or sand and cement screed? when you say 2/3mm in the joints, are these day joints in the screed?

[Dave]

It is normal in the screed hydration/curing and UFH commissioning to get hair line cracks in a cement screed.

The screed expands and shrinks as it cures etc... but to be safe it is wise to uncouple it anyway when tiling.

[Rich]

I would use a decoupling membrane

[BMD]

75mm sand cement screed...cracks appeared after UFH was turned on...joints widened after UFH was turned on...the floor is 6.5m x 7.5m

I don't know what you mean by day joints?

Just to clarify, I'm putting down travertine stone on the floor (not ceramic tiles).

I'm an amateur to this so I would appreciate more information on the use of decoupling membranes...should I use them on the cracks and on the joints...what products should I look at, tips for using them..costs etc.

[whitebeam]

I'd be using decoupling over the whole floor especially with travertine..

[BMD]

Also has anyone used a product called botament uncoupling membrane. In the case of the hairline cracks and joints do I simply take a strip of the membrane and lay it over the crack or should the whole floor be done?

[Phil Hobson]

Day joints are the finish of one days screed, and the begining of the next days lay. I would go with a decoupling membrane, as above

[whitebeam]

Also has anyone used a product called botament uncoupling membrane. In the case of the hairline cracks and joints do I simply take a strip of the membrane and lay it over the crack or should the whole floor be done?

Not one I've heard of but never had a problem with Ditra...

[Alan.P]

As above, definitely go with a membrane over the whole floor, there are a few to choose from, all do basically the same thing, use a flexible adhesive with a 6mm trowel to fix the membrane down.

This will give you an idea

DIY Tips: DITRA Installation - YouTube

[Tabby Cranks]

Ditra will cope with 3mm crack, as long as they dont get any wider.

[doug boardley]

Also has anyone used a product called botament uncoupling membrane. In the case of the hairline cracks and joints do I simply take a strip of the membrane and lay it over the crack or should the whole floor be done?

the whole floor should be done.

[BMD]

the cracks are only hairline...wouldn't even be 1mm...in the region of 0.25mm

The joints are wider ~ 2mm...they are not day joints...I'm not sure why they are there...they are only in the hall where there are no cracks

Is there any difference in how I should address joints and cracks?

Also has anyone heard of a membrane product called botament?

[whitebeam]

Whats a day joint ??

[Phil Hobson]

Hi Mark, Maybe I am using my own local terms, and confusing things. A day joint in my area is where a screed has been laid in one day. Then continued the next day, we call this a day joint, more likely to shrink causing cracking. Sorry for any confusion, caused by local terminology

[Del W]

As above.

[whitebeam]

With yer now..

[Ken Bruty]

If cost is putting you off a decoupling membrane, a Mapei product called Mapetex is a cheaper and much thinner option than Ditra Or Dural Ci, if you call Mapei on 0121 508 6970, they will be able to locate your nearest supplier for you

[jay]

any pics might help