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It is my intension to install a "between the joist" wet UFCH system with 18mm T&G ply 330mm porcelain floor tiles.
This is a ground floor and the sleeper walls are 1.2M apart.
I had planned to use 145mm joists which i believe are incredibly rigid over this span (deflection less than length/1000 at 400mm CC)
due to the minimum bend radius of the pipe the joist can be no closer than 350mm CC.
I was intending to use a weak biscuit mix over the insulation to improve performance making full height noggins a problem but was hoping that using T&G ply would negate this.
After speaking to BAL technical today they have told me that they do not support fixing to 18mm ply unless it is supported at no more than 300mm in every direction.
The problem it seems is possible deflection.
I would welcome comment/advise from anyone who has had experience of a similar installation or who otherwise has relevant expertise.
My alternatives it seems are to use 25mm ply which is very expensive and the UFCH people do not recommend over 22mm of timber deck from a heat resistance perspective or use a tile backer board which i believe are about £12 m^2 which will add £600 to my costs
PS.
Sorry for the long winded post.
This is a ground floor and the sleeper walls are 1.2M apart.
I had planned to use 145mm joists which i believe are incredibly rigid over this span (deflection less than length/1000 at 400mm CC)
due to the minimum bend radius of the pipe the joist can be no closer than 350mm CC.
I was intending to use a weak biscuit mix over the insulation to improve performance making full height noggins a problem but was hoping that using T&G ply would negate this.
After speaking to BAL technical today they have told me that they do not support fixing to 18mm ply unless it is supported at no more than 300mm in every direction.
The problem it seems is possible deflection.
I would welcome comment/advise from anyone who has had experience of a similar installation or who otherwise has relevant expertise.
My alternatives it seems are to use 25mm ply which is very expensive and the UFCH people do not recommend over 22mm of timber deck from a heat resistance perspective or use a tile backer board which i believe are about £12 m^2 which will add £600 to my costs
PS.
Sorry for the long winded post.
