In article , Kevin Brady wrote:
On new build housing, it is always required that joists are
doubled up when running parallel with bathtubs, for loading
purposes.

That's a new one on me too. Domestic floors are designed for an
imposed loading of 1.5kN/m2 - 30lb/ft2. A standard bath is 5'6'x2'4",
say 13ft x 30 = 390lbs. The bit of floor next to the bath is probably
taking next to no load while you're in the bath but is designed to
take another 390lbs. So you've got loads of strength there. In
addition it's usual to use the same size floor joists across the whole
first floor whose size is dictated by the longest span, and those
under the bathroom floor probably have a shorter span so loads more
capacity than the above.

What would be prudent would be to put a solid timber spreader under
the bath feet if they would otherwise just be bearing on chipboard,
perhaps midway between joists.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
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