F
Fluff
Hi all
I'm wondering if I could get any advice on a problem I have with an anhydritic screed recently installed.
Story:
~ 10 days ago, we had a screed laid over UFH pipes. It was supposed to be Truflow B. I had my hands full and also had to leave the house whilst this went down.
...The next day, I found that
- 1) the screed hadn't been laid to the right depth
- 2) it's not level
- also 3) that there's very little moisture coming out of it subsequently.
- and 4) I also think that I have a laitance layer which I was not expecting with Truflow B. I could be wrong - is there a way to know for sure if I have or haven't?
Details:
- Floor area is approx 32m square (4.5 * 7)
- Construction is block and beam + membrane + 150mm kingspan on top + thin membrane + 15mm UFH pipes laid with typical clips. Screed depth required was between 51 to 65mm. Screed depth laid is probably around 25 to 40. In some places, I imagine there's only 10-15mm screed above top of pipes (and less above top of clips)
- The guys barrowed the stuff in from the delivery mixer. They didn't use tripods (which I think is unusual). I'm pretty sure they didn't do a slump test (which is probably not unusual) and to me, the stuff just didn't look as watery as I was expecting. They used a dapple bar, but not sure if they went "across and then down".
- Have checked it reading a ruler off a laser and it's higher at one end than t'other, by ~10 to 15mm (aswell as being insufficient depth).
- Have tried putting a membrane down on the screed in the hope of seeing a bit more water and there is very little sign of moisture under the membrane after couple of days - I imagined this should be chucking out water during the first week?
Ideas to fix:
a) Another layer of pumped screed - this would depend on actually finding someone (reliable) to do it.
My concerns here are that
It'll need to be one suitable to bind to anhydritic screed. I'm not sure how strong these things are and also, I understand they have a max depth of 20mm. It doen't really seem like the right fix and as far as I can see, the stuff is only available in 20kg bags - looks like an expensive fix.
c) Other options
Any suggestions??
Other stuff
- The floor for the most part will not take any unusual weight....except .....at one end, I'll be building substantial bookshelves off the floor (say 2.5m high by 4 m long)- they'll be fully loaded.
- I'm putting an 18mm engineered laminate wood over it, which would reduce any point loading of the screed.
Any suggestions/advice on best way forward to "fix" this would be very gratefully appreciated.
(or any suggestions about better places to find an answer to this question)
I'm wondering if I could get any advice on a problem I have with an anhydritic screed recently installed.
Story:
~ 10 days ago, we had a screed laid over UFH pipes. It was supposed to be Truflow B. I had my hands full and also had to leave the house whilst this went down.
...The next day, I found that
- 1) the screed hadn't been laid to the right depth
- 2) it's not level
- also 3) that there's very little moisture coming out of it subsequently.
- and 4) I also think that I have a laitance layer which I was not expecting with Truflow B. I could be wrong - is there a way to know for sure if I have or haven't?
Details:
- Floor area is approx 32m square (4.5 * 7)
- Construction is block and beam + membrane + 150mm kingspan on top + thin membrane + 15mm UFH pipes laid with typical clips. Screed depth required was between 51 to 65mm. Screed depth laid is probably around 25 to 40. In some places, I imagine there's only 10-15mm screed above top of pipes (and less above top of clips)
- The guys barrowed the stuff in from the delivery mixer. They didn't use tripods (which I think is unusual). I'm pretty sure they didn't do a slump test (which is probably not unusual) and to me, the stuff just didn't look as watery as I was expecting. They used a dapple bar, but not sure if they went "across and then down".
- Have checked it reading a ruler off a laser and it's higher at one end than t'other, by ~10 to 15mm (aswell as being insufficient depth).
- Have tried putting a membrane down on the screed in the hope of seeing a bit more water and there is very little sign of moisture under the membrane after couple of days - I imagined this should be chucking out water during the first week?
Ideas to fix:
a) Another layer of pumped screed - this would depend on actually finding someone (reliable) to do it.
My concerns here are that
- whilst each layer will have a strong 3D "crystalline" structure, the 2D interface between the two layers will be nowhere near as strong. The UFH will be in the lower layer and as the temperature goes up and down that will cause some expansion and contraction in the lower layer faster than the upper layer - which I guess is likely to stress the weak bonding between the two layers. I presume it will help to some extent if I create a mechanical key between the two layers, but not sure what form this should take (sanding vs really really deep scoring)? Also - at the end of the day, is it a big deal if the two layers separate? The heat is still gonna come through and I guess the lower layer is already floating (on the kingspan+membrane).
- That said, due to current screed not being level, in some places the second layer may be as thin as maybe 15mm - and I'm worried this could split if loaded.
It'll need to be one suitable to bind to anhydritic screed. I'm not sure how strong these things are and also, I understand they have a max depth of 20mm. It doen't really seem like the right fix and as far as I can see, the stuff is only available in 20kg bags - looks like an expensive fix.
c) Other options
Any suggestions??
Other stuff
- The floor for the most part will not take any unusual weight....except .....at one end, I'll be building substantial bookshelves off the floor (say 2.5m high by 4 m long)- they'll be fully loaded.
- I'm putting an 18mm engineered laminate wood over it, which would reduce any point loading of the screed.
Any suggestions/advice on best way forward to "fix" this would be very gratefully appreciated.
(or any suggestions about better places to find an answer to this question)
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