Construction of Kevin McCloud’s DDV
A drop down veranda is a schizophrenic wall needing to be a floor. Each carries different structural loads and serves different purposes. Thus a drop down veranda is over spec for both jobs. Ours was built primarily as a floor to take the weight of many people at a party. As such it was built like one. Unlike the rest of the building the DDV frame is made from seasoned softwood to reduce weight. This is insulated in the conventional way and then boarded out. The exterior cladding is green western red cedar. I have calculated that the whole thing would be in the region of 500kg so Rob made his lifting mechanism capable of lifting this load. The majority of the weight is actually in the cladding, which will season, and loose weight over the first two years. With more time, a larger budget, or a desire to use more modern or high tech materials a lighter structure could be made. Also if such a thing is just for personal use by one or two people of course the internal structural work could be less substantial.
Worth checking out old wood horseboxes rear loading ramps as these are strong ( take weight of a large horse 700kg plus ) but as light as they could go with timber and the spring balances work well, but take your point re what you said in your post, sort of thought as much when watching show !
You would need less seasoned english oak than the softwood used to get the strength would it be lighter not sure on that one would have to do the maths,
Another way of doing this would to have lots of resting point when it was down then it could be a lighter construction !
The whole show was great fun to watch, many thanks guys
Arch Hamilton
Ps
The carpenters always do the most of the work as there the ones with the brains, keep on chipping
Did you consider a using a counter-weight to help with the lifting and dropping of the huge structure? A nice pulley system would have been epic :D.