Anhydrite moisture testing, putting some ideas to you Trusted People

[Andy Allen]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

cant see a private punter being happy to pay anyone to say his floors dry, unless this is all sorted before he agrees to have the screed installed..

ive not had much to do with these screeds, but everyone of them ive looked at, the customer has only ever been told you can tile it after x amount of weeks, no mention of bomb test or hygrometers....

 

[John Benton]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

Does the painter do the grouting ?

I was just throwing that in the mix to see who people think are responsible for preparation. Where does one trade stop and the next one start?

 

[bugs183]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

All good points everyone.
So by the generall feel so far you believe that is down to the builder or the screeder to take the responcibility of saying its ok to tile on.
Andy, this is the very problem that is happening people are being told these are fast track floors when it is not the case at all.
Now is this the screeder not telling the customer the facts or is this the screed manufacturer not telling them the facts?
Keep your views coming everyone as i'm interested in anything to do with these screeds as it's of benefit for all of us.

 

[DHTiling]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

The biggest issue IMHO is the ones selling these screeds, they push the benefits of installation speeds and the neutron strength over traditional screeds but why oh why do they not say they are slow drying and if UFH is installed they yes they can be force dried but this creates megga issues with shrinkage to joists and door casings etc etc.. the last 2 floors that i have had force dried, the builder and customer have said they were not happy about timber walls up stairs etc etc all twisting as the heat from force drying is unreal.

My question is this : If a green cement based screed can be tiled with say a vapour equalisation membrane like Ditra and why can't an Anhydrite screed be done the same way with a gypsum based adhesive ( no reaction with sulphates) , so Ditra stuck down with gypsum based adhesive and then the vapour is taken away within the mat as normal and then tile on top with your normal adhesive you use..

Gypsum to gypsum does not react, so why can't it be done that way..?

After all the 2 gypsum products can cure under the mat.

Answers welcome.

 

[Ajax123]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

I beleive that itis the main contractors responsibility to test the floor to make sure it is dry. In bs8203 which covers resilient flooring this is covered. However in bs5385 it is not. This leaves it open for contractual debate. The most it needs to cost is 80quid or thereabouts for a hygrometer. Most larger contracts or decent sized builds will absorb this sort of cost easily and frequently do. I am seeing more small builders taking up this option as well. I beleive it is then the tilers responsibility to carry out any necessary preparation prior to tiling I.e. sanding, vacuuming priming etc.

if this could be laid out in stone tablets then things wold be easy but unfortunately it is not and allow these things can be contracted by anyone. However it needs to be noted that in order to accept a contract a contractor should be able to demonstrate the necessary expertise to fulfil said contract. In other words if you don't know how to do a job dont do it.

 

[Ajax123]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

The biggest issue IMHO is the ones selling these screeds, they push the benefits of installation speeds and the neutron strength over traditional screeds but why oh why do they not say they are slow drying and if UFH is installed they yes they can be force dried but this creates megga issues with shrinkage to joists and door casings etc etc.. the last 2 floors that i have had force dried, the builder and customer have said they were not happy about timber walls up stairs etc etc all twisting as the heat from force drying is unreal.

My question is this : If a green cement based screed can be tiled with say a vapour equalisation membrane like Ditra and why can't an Anhydrite screed be done the same way with a gypsum based adhesive ( no reaction with sulphates) , so Ditra stuck down with gypsum based adhesive and then the vapour is taken away within the mat as normal and then tile on top with your normal adhesive you use..

Gypsum to gypsum does not react, so why can't it be done that way..?

After all the 2 gypsum products can cure under the mat.

Answers welcome.

If you trap too much moisture you'll impede the development of strength. However schluter, dural and genesis all say that ou can stick their mats to Anhydrite at 2% moisture. Now this must be done in Germany because that is where all of the development work is done. Unfortunately I have been unable in five years to find any membrane rep in the UK who will give any sensible and suitable guidance at all on what to stick it down with. When they have given any advice e.g. Schluter used to say use ardex p51 primer and flexible adhesive from ardex. Trouble is ardex in the UK say you can't do it. Big fat catch 22. This is a major issue for me and one of the reasons i Do not promote uncoupling too often except where stone is laid on top of underfloor heating. I do know that ditra and dural have been stuck down on many occasions with gypsum based adhesives from nicobond and from creative impressions.

 

[Gazzer]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

I beleive that itis the main contractors responsibility to test the floor to make sure it is dry. In bs8203 which covers resilient flooring this is covered. However in bs5385 it is not. This leaves it open for contractual debate. The most it needs to cost is 80quid or thereabouts for a hygrometer. Most larger contracts or decent sized builds will absorb this sort of cost easily and frequently do. I am seeing more small builders taking up this option as well. I beleive it is then the tilers responsibility to carry out any necessary preparation prior to tiling I.e. sanding, vacuuming priming etc.

if this could be laid out in stone tablets then things wold be easy but unfortunately it is not and allow these things can be contracted by anyone. However it needs to be noted that in order to accept a contract a contractor should be able to demonstrate the necessary expertise to fulfil said contract. In other words if you don't know how to do a job dont do it.

But isnt sanding supposed to be done 2 weeks after the screed was laid ?? I know it can be done later but by this time the kitchen may be fitted etc and the dust created is a nightmare.

 

[bugs183]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

These screeds are a right old hot potato. Everyone thinks they are the bees knees until the tiler turns up and has the cheek to ask if its been sanded and tested. All of a sudden everyone is pointing the finger at everyone else!!!
In my view i think is down to the screeder to lay the screed and come back and sand it, he's preparing a job for another trade to follow, as Sir says i don't tile and leave someone else the grouting.
But on that note surely the testing should be for him. He laid it, its got his name on it, hand over to the next trade when ready its deemed dry enough.
But there are so many conditions that are beyond his control ie room conditions, people stacking things in the room when told not too, spillages and million other factors that he can't control.
But on that merit for that same reason it's also not the tilers job! He certainly shouldn't tile before a test is done, but why should he be responcile for getting it tested????
I don't like the 'hood' method' as i know what numptys people are. Someone will kick the box or lift it up to see whats happening or the dog will run in and kick it.So Ajax what are your thoughts on a surey with a protimeter to get a study of the floor, and then a carbide bomb test on the dampest area found. I understand there are a few limitations with the protimeter, as they can possibly read the underfloor heating
Pipes, but as their tech guy says they will only read up as aposed to giving a lower moosture reading.

 

[Ajax123]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

But isnt sanding supposed to be done 2 weeks after the screed was laid ?? I know it can be done later but by this time the kitchen may be fitted etc and the dust created is a nightmare.

You do not sand to remove laitance. Tha is the screeders job and the reason why many of these screeds do not have a laitance on them. you are sanding in order to prepare the screed just as you should with sand cement and concrete screeds. This is to remove construction debris. Just as the decorator would sand the woodwork before painting. Done correctly it does not produce much dust.

 

[Gazzer]

Re: Anhydrite moisture testing, putting some ideas to you Trusted Peop

Ok hands up anyone who has ever sanded a concrete or sand and cement screeded floor ???