Need to raise floor 40mm

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popupstands

New Member
Hi I have laid 100mm insulation and around 60mm Screed but I need to raise it by another 40mm, do I need to seal screed? what is the cheapest and most sensible way to add 40mm

can I add another screed ?
would it be better to lay concrete with 10mm ballast for strength

Thanks in advance
 

flynnyman

Well-Known Member
Just wet it or even a cement slurry, I'm not sure what the minimum is for a screed on a solid floor but i think you will be safe :)
 

Jgreenplastering

Private Member
Has it got to be spot on 40mm?
Could you not use another 25mm insulation then 18mm ply to create a floating floor?

If you want it solid then it's needs another coat of screed with fibres in and a good wet down/sbr between the coats To make sure they bond.
How did you manage to get 40mm short in the first place?
 

Ajax123

Active Member
you can lay sand cement screed unbonded down to a minimum of 50mm or you can use an anhydrite screed down to 30mm minimum so 40mm is not really appropriate for sand cement unless you mechanically prepare the screed underneath. It is easily doable with anhydrite screed by simply laying a polythene membrane over the existing and pouring the anhydrite on top of it to the depth you need.
 

flynnyman

Well-Known Member
you can lay sand cement screed unbonded down to a minimum of 50mm or you can use an anhydrite screed down to 30mm minimum so 40mm is not really appropriate for sand cement unless you mechanically prepare the screed underneath. It is easily doable with anhydrite screed by simply laying a polythene membrane over the existing and pouring the anhydrite on top of it to the depth you need.
Is the 50mm not minimum for a floating floor?
 

malc

TPF Special Forces
Just wet it or even a cement slurry, I'm not sure what the minimum is for a screed on a solid floor but i think you will be safe :)
cement slurry ! has been a no no for 20 years, slurry dries quicker then the screed leaving the screed hallow.
 

malc

TPF Special Forces
lay a coat of sbr on the base, while the sbr is still wet apply the screed with sbr in the screed mix. you have then built up a key, screed the floor.
 

popupstands

New Member
I have a guy who will screed floor this saturday, I am having screed delivered ready mixed with fibres would it be worth asking if I could add some SBR to mix ? or would this be a problem
 
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