lumberroof
My roof truss timbers are 38mm x 72mm on 600mm centres with a 6m span. What's that in good old inches?
It seems a little skimpy to me; is this normal for a modern house? I am trying to do a rough dead load calculation. All the information I can find is for 4"x2" lumber. Mine are more like 1 3/4" x 3".
I think I read that 4"x2"s are actually smaller due to shrinkage so I have even less clue as to what my size is!
In the US, you can find rigid insulation panels of polyisocyanurate foam
and polstyrene foam
These can be cut to fit tightly between studs or rafters, can be flush with the face of the wood and are thick enough to be self supporting. They are usually sealed to the wood using broad tape, such as aluminum.
They are not cheap and not very strong if hit, but have a very high R value.
They also could be covered with either very thin drywall or the new ultralight drywall.
I believe this article should give you some answers:
http://www.sbcmag.info/article/2012/truss-storage
In short, it all depends on how the trusses look after the time. The article says that they may be left out for a week max and then should be covered, but any time after that just comes down to what the current weather conditions have done to them.
Best Answer
Using Google you can do conversions. Type:
into Google and it will give you the conversion as the first result.
Your sizes come out at
Now, the reason these are smaller than the quoted sizes is because wood is not measured in the finished size but in the original size. So a piece of wood that's quoted at 4" x 2" will actually be something like 3.5" x 1.5". This isn't a problem because everybody* knows this.
The calculations should take this into account.
* for some value of "everybody".