Anhydrite moisture testing, putting some ideas to you Trusted People

[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 ???

 

[Ajax123]

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.

Screeds are not selected to satisfy the proclivities of the tiler. There are many reasons why anhydrite is selected over other methods. The tiler should be checking if the screed is clean and free from debris anyway. This is not an extra responsibility...

This idea of responsibility is a moot point. A facile argument really as responsibilities should be outlined in a contract. The tiler can decide what responsibilities he wishes to accept just as the main contractor, the screeder or the client can. If what you want to accept does not meet the requirements of what the person employing you wants then you won't win the contract. I cannot see why there is such a fuss here.

I guess I shall continue to encourage screeders to take on the floor coverings and vice versa as I have in the past. That way the same contractor takes both bits. In my experience when this happens it rarely goes wrong. This already happensy in the larger contracts to some extent. The reason this is important is simply because many existing tilers don't seem to want to accept that these screeds are no less difficult than traditional screeds. When the screeder takes on the tiling as well I get none of these questions because he knows what he is looking at and jus gets on with the job at the appropriate time.

It is simple.

1. Dry it making sure any underfloor heating has been comissioned and run.
2. Clean it
3. Vaccuum it and check it is sound and flat
4. Prime it (if required)
5. Tile it.

If anything is wrong bat it back to the main contractor to sort unless you are contracted to sort it. In which case do exactly that.

These are exactly the same steps as you should use with sand cement screed.

Use compatible materials. Bobs your uncle.

 

[Ajax123]

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 ???

Just because you don't does not mean you shouldn't.

 

[bugs183]

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

Cheers for the replies Ajax, i think we totally understand that these screeds are not here to satisfy us, and do realise that the screed plays a wider part in the build than just a thing for us to stick our tiles onto, but as i've said before i think you need to try and put yourself in our position.

You obviously get involved in some very large contracts and in this field your approach is bang on.
The tenders are drawn up, everyone sits down, talks the jobs over and contracts are drawn up as to whose being paid for what.

I love commercial work for this very reason, but i have not yet tiled a floor in any commercial or site enviroment and i bet a huge percentage of the guys on here haven't either.
We get mainly private or small builder jobs. We get a phone call off Mr Builder or Mrs Smith and you get asked to quote on a job, then you look at the job, oh it's anhydrite.
So you ask has it been sanded and tested, you can bet 99% of these jobs haven't been and the customer and builder has no idea it needed it, everyone shrugs their shoulders.
The screeder is history, the architect that spec'd it doesn't want to know and so here we go it's now the tilers job to sort all these things out, no amount contractual rangling helps here.

So back and forth we go a testing, telling the customer it isn't ready, this can go in for weeks and weeks in which case it can get very awkward between customer and tiler, the customer justs wants their room tiled , and the tiler has wasted money on diesel and time.

This is a fact and it is what we are facing, it is a very different world to a commercial or site enviroment.

And to add the job i've just done was sanded with a Raimondi Maxititina which i sourced from Trimline, it sanded really well and made no airborne dust at all, a quick vacuum up and you wouldn't have known it had been done.

 

[Gazzer]

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

Couldnt have put it better myself Bugs, Really Alan you do need to come from around that side of the desk.
We are only small people in the whole story and do tend to get kicked about.


Bugs did you buy the sander or hire it ?

 

[Ajax123]

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

I'll get me boots on now sir... seriously though I spend as much time defending tilers dealing with these screeds as I do defending screeders. Not from behind a desk althouof course that does happen occasionally but mostly via site visits. At the end of the day if I see something being done wrong I will say so. If a client of or builder is trying to cut corners and persuade the tiler to tile innapropriately the I shall tell him so and actually often do. Likewise if I see that a tiler or even a screeder has done soepmething wrong I will say so and the converse is also true.

 

[Spud]

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 ???

I have And its an awful job ,even with a dustex hoover and preseperator drum you will still be covered head to toe in fine white powder sanding off an anhydrite

 

[Gazzer]

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

I have And its an awful job ,even with a dustex hoover and preseperator drum you will still be covered head to toe in fine white powder sanding off an anhydrite

Yes but what about sanding sand and cement screed ?

 

[Diamond Pool Finishers]

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

HA HA, stick to traditional screeds they are a lot less trouble and people understand them , as i have said many times the americans have done all this and bind them off , still you can lead a horse to water !!!!:smilewinkgrin:

 

[bugs183]

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

I've been that intrigued/sad looser about this topic i've looked at US and Aussie forums on this screed, and yep the US guys avoid it like the plague too.
They also use into situ probe testing to measure the moisture content and don't rate the hood test at all!

 

[The D]

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

I’m not the most knowledgeable tiler in the world but I have been tiling a few years now. I have never in my life sanded a sand and cement screed floor. I have never seen any literature saying that it is necessary. I have not seen it in BS5385(I’m not saying it is not there just I have never seen it) I have not even seen it in anything from the adhesive manufacturers. I have 2 uncles 4 cousins and 2 nephews all in the tiling game and non of them have ever sanded a sand and cement screed floor. I have also during my time as a tiler worked along side tilers from all over the country and seen all sorts weird and wonderful tiling techniques but never come across anyone that dose that.
concrete is a slightly different beast as if the person installing it did not trim the fat then that would need removing but in my experience to do that needs a bit more than a sand over