Gypsum based tile adhesive

[Ian]

I did a floor with GBTA (from Creative Impressions) a couple of months ago and took a few pics along the way and thought I'd share them with you all.

A bit of background on this particular floor first.

It was pumped in on April 22nd (2011) at a thickness of 50mm and left to dry for 3 months (longer than necessary but one floor was a basement which held the moisture more than expected when tested with a hygrometer), when we were satisfied that it was dry enough the heating was commissioned and the laitence (which was minimal) was sanded off using a mechanical sander with a metal abrasive pad,



This process removed the laitence and created a lot of dust! It was then hoovered very thoroughly ready to be primed.

ALWAYS WEAR A DUST MASK AND VENTILATE THE AREA YOU ARE WORKING IN!!!

After sanding and hoovering the area to be tiled was then given a 1st coat of the GBLC primer 24 hours before tiling was due to commence.



Once the first coat was fully cured a, second coat was required however, this was to be done in smaller sections (5 m2 at a time) and was tiled on whilst still tacky.



The adhesive itself was very easy to use and had a reasonable pot life (30-40 mins), one thing I will say is that when mixed in the bucket to the correct ratios, it looked too wet but, when troweled out held its ridges and didn't slump at all. With a 10mm round notch and back skimming I was getting between 5-6 m2 from a 25kg bag.



Anyone who has never prepped and tiled on a gypsum floor and are wary of them, I will say that if you follow the recommended curing times, prep the floor in the correct manner and tile using the appropriate products, you have nothing to fear. These floors are becoming very common now so, you will all have to face them sooner or later!

 

[Spud]

What was the cost per m2 of the prep materials and the adhesive compared to a normal screed Job Bri and did the screed company organise the sanding or was that down to you as in europe this is always the responsibility of the screeding company not the tiler

 

[Ian]

The sander was supplied by the screeding company but, we (the client and myself) did the sanding. The cost in comparison to a sand and cement screed would be quite a bit more, I would say that, based on primer and adhesive, a cement screed would be around £3 per m and using these products would be £6/7 per m.

 

[Spud]

I was always told that the sanding should be done as soon as possible after screeding as the longer its left the harder it is to remove the laitence and reveal the aggregate,Ive never tiled on a low laitence gypsum screed, what's the benefit of this over to conventional gypsum screed ?

 

[Ian]

I was always told that the sanding should be done as soon as possible after screeding as the longer its left the harder it is to remove the laitence and reveal the aggregate,Ive never tiled on a low laitence gypsum screed, what's the benefit of this over to conventional gypsum screed ?

This was the 1st one I've ever done Gary and to be honest it was a steep learning curve, the laitence on these low laitence screeds is so minimal that the purpose of the sanding process is just to give the surface a key. I was given a lot of expert advice along the way from Alan Jackson (Ajax) and Sabo from Creative Impressions. The laitence was sanded early on (4 weeks I think) by the client but, only by hand, the mechanical sanding was done as a belt and braces back up as the plasterers had been in and 2 months had passed since the original sand.

 

[DHTiling]

Unless the screeder over wets them , then it becomes harder.. just the friable i am on about..

 

[macten]

If you are mechanically removing the laitence and priming - can you not just use your regular cement based addy of choice?

 

[Gazzer]

You can according to some adhesive manufacturers spec but you have to be 101% sure with the priming.
Gypfix or GBTA seems a better way for me.

 

[Ian]

If you are mechanically removing the laitence and priming - can you not just use your regular cement based addy of choice?

I did a couple of sample tiles on a primed area, one stuck with GBTA and one stuck with flexible cement based, then left them for 3 days. The GBTA needed a hammer and chisel to get it up and the cement based needed a wallpaper scraper! So yes some manufactures claim cement based can be used but for me, no way I'll take the risk

 

[Ajax123]

I did a couple of sample tiles on a primed area, one stuck with GBTA and one stuck with flexible cement based, then left them for 3 days. The GBTA needed a hammer and chisel to get it up and the cement based needed a wallpaper scraper! So yes some manufactures claim cement based can be used but for me, no way I'll take the risk

That is pretty typical of my experience as well.