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Hello all. This is a technical query relating to a proposed garden room in Scotland. Specifically, to racking loads and the number of openings I'm allowed. I'm sure I've got this wrong but I'm tearing my hair out here. Well, what little hair I've got left! 
I have submitted an application for a building warrant, given that the size of my proposed garden room is greater than 8m2, and that I'd like to put sanitaryware in (drawings include the proposed layouts).
In Scotland it is necessary to comply with a little-known document called Small Buildings Structural Guidance (link here). In this document there are a number of sections on timber frame buildings that are linked. Specifically, 1.E.15, 1.E.17 and 1.E.18. These deal with racking resistance (i.e. wind loads) and the number of openings that a certain building can have on an external wall. Anyway, I've been through the sections and done the calculations. Bear with me here.
Based on where I am (wind and snow loading) in the country, the 'R' values for my max length and width come in at R5 and R1 respectively. See below screen grab, from 1.E.15.
What does this mean in the real world? I'll get to that in a second. In the meantime, according to section 1.E.17, I need to work out my total window and door openings sizes in the racking wall (i.e. the wall where my window and doors are situated).
So I've done the calculations and the total size of my openings for my 6 x 4 garden room in the raking wall amount to 27.9% of the total area.
"So, what's the problem?" I hear you ask. Well, this is where I can't work it out. According to section 1.E.18, based on my construction method of timber frame studding (C16 timber at 600mm centres, with 11mm OSB3 nailed at 150mm centres), I can only have openings totaling 10% of my wall size.
Now, this is manifestly bonkers. Every garden room ever built has either bi-fold doors or large expanses of glass. It's hardly as if my openings are excessive. On the contrary, they're really conservative.
I've come to the conclusion that I'm completely overlooking something, or I've terribly miscalculated. However, I've gone over my design time-and-time again and simply can't make sense of it.
I guess when the building warrant decision comes back I'll see what's what, but in the meantime if anyone has any insight I'd be very, very grateful!
Thanks,
Jack.
I have submitted an application for a building warrant, given that the size of my proposed garden room is greater than 8m2, and that I'd like to put sanitaryware in (drawings include the proposed layouts).
In Scotland it is necessary to comply with a little-known document called Small Buildings Structural Guidance (link here). In this document there are a number of sections on timber frame buildings that are linked. Specifically, 1.E.15, 1.E.17 and 1.E.18. These deal with racking resistance (i.e. wind loads) and the number of openings that a certain building can have on an external wall. Anyway, I've been through the sections and done the calculations. Bear with me here.
Based on where I am (wind and snow loading) in the country, the 'R' values for my max length and width come in at R5 and R1 respectively. See below screen grab, from 1.E.15.
What does this mean in the real world? I'll get to that in a second. In the meantime, according to section 1.E.17, I need to work out my total window and door openings sizes in the racking wall (i.e. the wall where my window and doors are situated).
So I've done the calculations and the total size of my openings for my 6 x 4 garden room in the raking wall amount to 27.9% of the total area.
"So, what's the problem?" I hear you ask. Well, this is where I can't work it out. According to section 1.E.18, based on my construction method of timber frame studding (C16 timber at 600mm centres, with 11mm OSB3 nailed at 150mm centres), I can only have openings totaling 10% of my wall size.
Now, this is manifestly bonkers. Every garden room ever built has either bi-fold doors or large expanses of glass. It's hardly as if my openings are excessive. On the contrary, they're really conservative.
I've come to the conclusion that I'm completely overlooking something, or I've terribly miscalculated. However, I've gone over my design time-and-time again and simply can't make sense of it.
I guess when the building warrant decision comes back I'll see what's what, but in the meantime if anyone has any insight I'd be very, very grateful!
Thanks,
Jack.
