Maximum Wall Height for Single skin garage with piers

FibCouple · 16 May 2019

Hello all

We have a single skin 7.8X7.8 mtrs double, attached garage with a flat roof. The walls are single skin brick, with piers at 2.6mtrs centres. Wall plate height is 2.3mtrs. We are converting it to habitable accommodation & are looking for options to change the flat roof to a vaulted roof with scissor trusses. Gable wall will then be nearly 3.8 metres high. Our foundations are good for single storey & soil is good too as seen by building regs.

How high can a single skin brick wall with piers (22X11) go & be stable? Will we have to provide inner clockwork on that wall to support? We are building inner stud walls on the perimeter & have a solid slab of concrete with no cracks.

Or is there something like a lightweight wood-framed gable wall (with hung tiles to match the house)??

Cheers

Fib

Leofric · 16 May 2019

You could have a vertical tile hung timber frame gable wall but there other things to consider ,of course ,if you are converting the garage to habitable accommodation.

FibCouple · 17 May 2019

Leofric said:
You could have a vertical tile hung timber frame gable wall but there other things to consider ,of course ,if you are converting the garage to habitable accommodation.

Thanks Leofric! I should have mentioned we have the insulation, ventilation, inner stud walls, floor & ceiling etc all worked out & agreed by building regs. Its just that we were thinking just raising the flat roof but are now considering dual pitch roof.

^woody^ · 17 May 2019

The walls are stabilised by the roof.

FibCouple · 17 May 2019

Thanks for the replies guys & gals.

Another question - we have a single brick wall & if we install scissor trusses, the heel will sit on wall plate on the (exterior) brick wall. Presumably this will have implications that the wall plate can rot, especially as we live on the coast. Thoughts?

Cheers

^woody^ · 17 May 2019

It will be hidden by the fascia, but as long as it can dry off if gets wet (which it should not be able to do in th efirst place) its OK. Use tanalised/treated anyway.

tony1851 · 17 May 2019

Google Approved Document A; the suggested dimensions and details for single-skin detached buildings are all in there.

FibCouple · 17 May 2019

tony1851 said:
Google Approved Document A; the suggested dimensions and details for single-skin detached buildings are all in there.

Thanks. I did have a look on that document couple of days ago (and the older version from 2004 as well) but couldn't work out if it applies to my situation. Our garage is attached as well. Guess I will keep looking and reading - I am sure building regs will tell me & the builder when the time comes but wanted to do my due diligence.

tony1851 · 17 May 2019

As the garage is attached, you need first of all to look at the proportions of the structure on p.14 (2004) edition. There is also table 3 (p 15) giving minimum thicknesses of certain walls relative to their length and height.
There doesn't seem to be mention of half-brick thick walls with piers - they are not normally used for habitable buildings; much is down to common sense and experience. If the wall plate is securely strapped down to the brickwork, the weight of the roof will be a restraining factor helping to stabilize the wall.
Other than that, it's down to calculating the maximum heighth of the wall by treating it as a panel subject to horizontal wind load, and doing the number crunching but that's an SEs job.
But if you have a reasonable inspector, and the wall isn't taken up too high, and well-strapped to the roof, hopefully common sense should prevail.

FibCouple · 17 May 2019

tony1851 said:
As the garage is attached, you need first of all to look at the proportions of the structure on p.14 (2004) edition. There is also table 3 (p 15) giving minimum thicknesses of certain walls relative to their length and height.
There doesn't seem to be mention of half-brick thick walls with piers - they are not normally used for habitable buildings; much is down to common sense and experience. If the wall plate is securely strapped down to the brickwork, the weight of the roof will be a restraining factor helping to stabilize the wall.
Other than that, it's down to calculating the maximum heighth of the wall by treating it as a panel subject to horizontal wind load, and doing the number crunching but that's an SEs job.
But if you have a reasonable inspector, and the wall isn't taken up too high, and well-strapped to the roof, hopefully common sense should prevail.

Thank you so much for the pointers - very helpful & reassuring. Trying to make sense. For some reason 2004 document is so much more detailed in parts. The structural engr. will hopefully soon visit the site & give his input & the Building reg guy seems to be sensible & one who tries to find solutions rather than obstruct. So hopefully......fingers crossed.

^woody^ · 18 May 2019

The important thing with gables is tying them in to the roof structure, as it's disturbingly common for the gable to be pulled out by strong winds. And this is more of a concern than anything else.

This is difficult to do with single skin brickwork, so anyone designing this garage for you should bear this in mind.

FibCouple · 19 May 2019

^woody^ said:
The important thing with gables is tying them in to the roof structure, as it's disturbingly common for the gable to be pulled out by strong winds. And this is more of a concern than anything else.

This is difficult to do with single skin brickwork, so anyone designing this garage for you should bear this in mind.

Cheers! I will bear that in mind

diynot

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Maximum Wall Height for Single skin garage with piers

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