Anhydrate screed prep spec check

[poynton phil]

First time i'v come across a anhydrate screed, and the screed people left these instructions for the tiler (me)So I just want to check if this is the right way to go. The screed is heated, and tiles are 800x800 porcelain

Sand the sheen off the floor, with a floor sander.

Prime with, 1 or 2 coats of SBR.

Tile floor using a SPF ahesive.

Any advice is appreciated. Thanks

 

[Chalker]

First time i'v come across a anhydrate screed, and the screed people left these instructions for the tiler (me)So I just want to check if this is the right way to go. The screed is heated, and tiles are 800x800 porcelain

Sand the sheen off the floor, with a floor sander.

Prime with, 1 or 2 coats of SBR.

Tile floor using a SPF ahesive.

Any advice is appreciated. Thanks

Good advise.
Make sure it's dry.

 

[Stef]

1st thing is check to make sure it's dry, hygrometer, & check when it was poured.
Get it sanded as quick as possible as this will aid drying time. Get windows & doors open to let out moisture from building.
I would give it one coat of TileMaster prime plus mixed at a 4 or 5 to 1 ratio & I would use TileMaster AnhyFix.
I would keep away from a cement based addy on top of a calcium sulphate screed.
There are a few compatible gypsum based adhesives out there, I like AnhyFix & that's what I use when going over a gypsum screed.

 

[nybor62]

the low latence screed does not need sanding so ive been told , gypfix i here is good , not used it myself , deffo not cement based addy imo

and and who ever you get the addy from should also do the recommended primer, and yes check for moisture in the screed

 

[Stef]

the low latence screed does not need sanding so ive been told , gypfix i here is good , not used it myself , deffo not cement based addy imo

and and who ever you get the addy from should also do the recommended primer, and yes check for moisture in the screed

Rob I'm certain the low laitance needs sanded, I can remember a post from Alan about this & he stated all these screeds must be sanded...

 

[CJ]

I checked on a job last week, with the screeder who actually did the floor 10 years ago.

Hemi hydrate. He said do not scabble it, and prime with acrylic primer.

 

[nybor62]

alan should know stef, it was the main contractor who mentioned it to me , it was lafarge screed .

 

[Stef]

alan should know stef, it was the main contractor who mentioned it to me , it was lafarge screed .

If I'm stuck on any kind of screed then Alan's the go to man..
He knows these screeds inside out & will probably reply when he sees this..

 

[Ajax123]

the low latence screed does not need sanding so ive been told , gypfix i here is good , not used it myself , deffo not cement based addy imo

and and who ever you get the addy from should also do the recommended primer, and yes check for moisture in the screed

Yes it does. All anhydrite screeds require sanding. In fact the advice of the tiling association and the contract flooring association is that ALL screeds and concretes require mechanical abrasion as part of the preparation.

My main concern about your having been told it does not need to be sanded is if there is a failure, ALL the adhesive manufacturers instructions say sand it and you say you did not sand it no one will stand side by side with you to defend you.

 

[Rookery]

I'd sand the screed, prime twice and then fix with Keraquick.

 

[Ajax123]

I'd sand the screed, prime twice and then fix with Keraquick.

I would use a gypsum based adhesive to make certain it sticks...

 

[poynton phil]

I will be using a floor sander on this floor, but as anyone any sort of idea, how long it will take, in total there will be about 150msq. Also I'v heard that shower room floors need tanking, is this correcect. Thanks.

 

[Ajax123]

I will be using a floor sander on this floor, but as anyone any sort of idea, how long it will take, in total there will be about 150msq. Also I'v heard that shower room floors need tanking, is this correcect. Thanks.

Sanding should only take a couple of hours. I've done 500m2 in an afternoon before. Not heard that about shower room floors but if the tiles will allow water through it would be a good idea.

 

[mike1979]

As the lads said !!!!! I do loads of them and they are a joy to tile on really flat I sand it of Hoover it and prime it I used to use the granfix gypsum based adhesive but find it sets too slow so I use nicobond gypsum adhesive love the stuff !!

 

[Spud]

Sanding should only take a couple of hours. I've done 500m2 in an afternoon before. Not heard that about shower room floors but if the tiles will allow water through it would be a good idea.

Hi Alan which machine did you use to achieve 500m2 in 4 hrs as the floors I have done taken a lot longer and I have some decent equipment

 

[Chalker]

This one!, only joking:lol:

 

[Ajax123]

Hi Alan which machine did you use to achieve 500m2 in 4 hrs as the floors I have done taken a lot longer and I have some decent equipment

Standard STR floor sander with either 60 or 30 grit paper. If the screed is particularly hard e.g. If the Laitance hasn't been removed before the heating has been commissioned if can be harder. In this instance a copper disc could be used instead of paper.

 

[poynton phil]

How dusty of a job is this?

 

[High Peak Tiling]

from Jobs i have done, it is a dusty job but I found most of the dust stays settled instead of airborn.

 

[High Peak Tiling]

I have only used belt sanders.. which took a long time

 

[Ajax123]

I have only used belt sanders.. which took a long time

I have seen belt sanders used and I beleive they do create more airborne dust than rotary str sanders. This is because the belt sanders move faster. They also "skid" over the surface due to them being lighter and if weighted to improve grip can rut the screed. The str sander is best and if dust is an issue you can get one with a integral cpvaccuum function although I see very few of these used.

 

[High Peak Tiling]

I have seen belt sanders used and I beleive they do create more airborne dust than rotary str sanders. This is because the belt sanders move faster. They also "skid" over the surface due to them being lighter and if weighted to improve grip can rut the screed. The str sander is best and if dust is an issue you can get one with a integral cpvaccuum function although I see very few of these used.

When I was on sites near London several years ago I saw the upright sanders being used and they just hoovered up after themselves

 

[Ajax123]

When I was on sites near London several years ago I saw the upright sanders being used and they just hoovered up after themselves

Yup...

 

[Spud]

Alan I have found if there is any moisture in the anhydride that sand paper discs clog and grip the floor causing the rotary machine to overheat, when taking the laitence off of anhydrite floors carborundum stones work far more effectively on a rotary machine and as they have a smaller surface area on damp areas they don't strain the motor or gear box of the machine unnesscesarily
dust is a big issue and we went over to dustless grinding and bagged dust collection I really think saying a 150 m floor can be done in an afternoon with a rotary machine is un realistic but if you have done it then I must be doing something wrong and would appreciate some tips
we have tried several types of machine and spent a fair amount of money tooling up for anhydrite prep work and all floors are different I suppose depending on the product and installers

 

[m3fitter]

spoke to Ardex help desk........... we de scabbed it with a brute, primed it well, and fixed ditra after 3 days......