1/2" screed ?

qazxsw

Hi folks,

I've ufh upstairs over timber joists,

I used 50mm battens at 12" centres on osb, but or a number of reasons the screed I put down isn't level enough to lay timber floorboards on. (won't go into the details why here)

I was thinking of ripping a sheet of 1/2" ply into 50mm strips and screwing these to every second 50mm batten (making sure the new strips are level / straight, etc ) and filling between with a sand/cement screed.

I'm worried that the 1/2" screed would start cracking, etc when the heating is turned on and I'm walking on it before the floorboards get laid.

any opinions or other suggested solutions or has anyone come across a similar problem.

I already have 50mm concrete on top of 9" x 2" joists so obviously I can't just pour another two inches.

yop

We have a similar setup, 50mm battens screwed to OSB, 25mm insulation between the battens, the UFH on top of that and 25mm or so to bring it up level with the battens, the heating is on 3 weeks now and no issues have occured bar in one spot where there was no battens and the screed dept was less than 25mm

Pataman

Any issues with the weight of the screed upstairs on the timber frame?

yop

I have to inform the TF company that I was doing this, the added in more timber to take the stress.

Vertical

Sounds like we are doing something similar:

I'm building a house from concrete/steel. The upstairs 9x2 joists are notched into a steel RSJ frame (the tops of the joist are about 25mm proud of the supporting steel), max joist span is approx 2.5m. Its very strong so I'm not worried about the weight of the floor upstairs.
The floor will consist of ply directly onto the 9x2 joists giving a level surface. Then plastic/UFH piping/screed (approx 50mm)/steel mesh.

My question is:
Is it necessary to insulate an upstairs screed floor?
I see my options as :
A. Just use insulation on the edges of the screed to reduce heatloss to walls, insulate around RSJ supports to prevent heat being drawn away from the screed along the steel.
B. As per A but also slot rigid insulation between the joists.
C. As per A but use rigid insulation on top of the ply under the entire screed.

Any comments appreciated...

rooferPete

Hi q...

Sika may have a solution to your problem, 1/2" is too little for a sand / cement screed and too much for average levelling compound, try www.sika.ie or call them, they are very helpful.

.

Pataman

Thanks for the info guys, a mine of information as usual. Who needs builders when you have boards.