New screed meets old screeds - Tile Advice

[Cranbrook]

Unusual (for me) job I've been to quote for this week where the customer has had a large extension added to a bungalow and has made a large open plan kitchen by utilising a hefty RSJ.. customer has also had another extension to the side to make a smaller utility room.. anyway, the thing is, the new screed in the large extension is a pumped AH and the smaller extending is a traditional sand cement screed. The existing screed is a sand cement that was previously tiled.

My question is, what would everyone do in this kind of instance?
P.s, tiles are 60 by 60 polished porcelain the customer tells me

 

[Flintstone]

Whats pumped ah?

 

[acaciaguy]

Is it pumped anhydrite ?

If so it’s a more complex / modern version of sand and cement - quicker setting and other inproved properties (apparently)

Is the floor level across the different area?

 

[Cranbrook]

I didn't have my laser to do a thorough inspection, but where tiles had been removed from the existing screed, there is definitely repair work to be done, so I'm leaning towards latexing the whole lot.. thoughts?

 

[Cranbrook]

Whats pumped ah?

Anhydrite mate

 

[LM]

Anhydrite mate

I didn't have my laser to do a thorough inspection, but where tiles had been removed from the existing screed, there is definitely repair work to be done, so I'm leaning towards latexing the whole lot.. thoughts?

Your’e gonna have to treat both sections as two separate floors, prepare and level accordingly then have a soft expansion joint between the two areas.

 

[Flintstone]

As Lee says, expansion joint in-between the two.

 

[acaciaguy]

Sounds a good plan to me

 

[acaciaguy]

Lee Mac. Is there a slc or similar system that can be used on both surfaces to turn them in to “one” for tile fixing? Just a thought. I appreciate this may change heights of floors.

 

[Cranbrook]

Lee Mac. Is there a slc or similar system that can be used on both surfaces to turn them in to “one” for tile fixing? Just a thought. I appreciate this may change heights of floors.

This was my train of thought.. I'd like to avoid an unsightly expansion joint as it will ruin the look of the kitchen diner imo

 

[LM]

You can use normal fibre slc’s on an anhydride screed with the correct priming after proper prep but the necessity for an expansion joint is that the two substrates are of a different composition and in turn will behave differently, ie: contract and expand at different rates. So an expansion joint in the correct place is a must or else your’e taking a chance.

 

[LM]

This was my train of thought.. I'd like to avoid an unsightly expansion joint as it will ruin the look of the kitchen diner imo

A colour matched silicone or the like the same width as the grout joint installed correctly isn’t really visible so it’s no big deal.

 

[Cranbrook]

You can use normal fibre slc’s on an anhydride screed with the correct priming after proper prep but the necessity for an expansion joint is that the two substrates are of a different composition and in turn will behave differently, ie: contract and expand at different rates. So an expansion joint in the correct place is a must or else your’e taking a chance.

Thanks for the information Lee that's very helpful, out of interest, if they were the same material screeds but laid years apart, would the same still apply?

 

[LM]

Lee Mac. Is there a slc or similar system that can be used on both surfaces to turn them in to “one” for tile fixing? Just a thought. I appreciate this may change heights of floors.

There are companies out there that reccomend strips of uncoupling membrane in localised areas instead of expansion joints but even at that it’s with the same substrate throughout. If you change the substrate then you will have movements at different rates.

 

[LM]

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