Keeping the weight down

No, I'm not talking about dieting (although believe me, I could do with going on one :oops:)

I'm building in a first-floor room and so, unlike those building in a garage or a ground-floor room with a concrete underfloor, I have to work within a weight limit. My research shows that a house in the UK is required to support an imposed load on an upper floor of 1.5 kiloNewtons per square meter (that's about 153 kilos). My shell will be built on a load-spreading base of 4.3 sqm, so my max weight is 650kg. Sounds like a lot, but once you factor in a whole load of wood panels and batons plus gear plus people, you can see how you'd get pretty near the limit.

Now, since my day job is in the property industry (specifically surveying, although I myself am a software development manager), I know a few people who know a few things about buildings. They reassure me that, even in today's penny-pinching house builds, floors are usually built above tolerance, and that older properties - my flat is in an Edwardian (early 1900s) house conversion - will have much sturdier floor joists and will take more weight.

Still, the thought of one evening crashing through the ceiling into the downstairs flat, killing myself and my neighbours into the bargain, has been preying on my mind...

So I've decided to throw out all the MDF stuff I've currently built (admittedly, not that much so far, I mostly have raw MDF sheets still) and go with plywood, which is around 30% lighter, and a much more frame-based construction technique to cut down on the amount of structural panelling I have to use. I want to get it so I can have two or three observers standing on the base or in the enclosure and still keep the load under 550kg. With plywood, this should be possible...

Anyone else had weight issues like this? If so, what did you do? Or did you just build it and hope?

NH