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I am considering under floor heating (UFH) for an existing bedroom on the first floor as well as for 3 new bedrooms to be created when I convert an existing single storey extension by adding a further floor.

It appears that the most cost efficient way of installing the pipework is to cover it with a screed (25mm thick has been suggested by various suppliers of UFH) as heat transfer plates are very expensive to install and require a higher pipe temperature than screed.

However screed will add approximately 25kg per sq. m which needs to be carried by the joists.

I have seen the building regs Table A1 which suggests acceptable loads and span for joists of various dimensions - but this is expressed as follows:

"This table is for a dead load of more than 0.25 but not more than 0.50 and allows for an imposed loading of no more than 1.5 kN/sq.m."

Is there a simple way of converting this approximately to weight in kg/sq m?

(NOTE: I appreciate the best way to get a technically correct indication is to pay an architect, but at the moment I would like to get a rough idea in order to determine if the UFH route is practical to pursue further before spending money possibly needlessly.)

There is yes, divide the kN by 10

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