Ettringite formation over gypsum screed

[Ajax123]

not being picky or anything but are you sure it is 40mm. It is just that if it is a wet underfloor heating system it is likely to be a 15mm(ish) pipe diameter. Most anhydrite screeds look for 30mm cover to pipes so that is 45mm. The pipes are often held off the deck in pipe clip tracks which lift it off by another 5mm hence the 50 to 55mm suggested. If it is 40mm then fair enough but thought I'd check. There are some systems with thinner pipes so I may be barking up the worng tree but as you say 1 step ahead is no bad thing.

 

[Brindle]

The customer says 40mm, the firm is here Wednesday to measure the moisture so as long as it's dry happy days. Not dry = no work

 

[Ajax123]

Hi Brindle

Just following up the previous posts to see if you have been able to start this job yet. How has it gone....

I came across a primer the other day from Dunlop - universal bonding agent it is called. Anyway I got it from a stone specialit who has used it on all his jobs including quite a few anhydrites - he has never had a failure....

might be worth checking it out.

Alan

 

[Brindle]

Hi Alan, I went with the specific manufacturers recommendation for Anhydrite screed which was Norcross (customer bought) and they specify 3 x coats of SBR, 1:4/ 1:3/ 1:2 if still absorbant. I went through all the risks with the customer and pointed out all info as provided by yourself and manufacturers. I removed all laitence, and followed the priming procedures to the letter. Am now about 50m2 through the tiling, going ok so far....

I was going to post an update end of this week. I'll try and upload a few piccies

Cheers
Gareth