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By MikeG.
devonwoody wrote:If the council get concerned re timber sheds near a boundary why is timber fencing no less a risk? :evil:

Years of experience has taught us, devonwoody, that fences catch fire rarely, and that buildings catch fire more often. You can't have electrical faults or store flammable liquids or gas in a fence.
By Hobbo
I'm really struggling to find a straight answer on the maximum size of an outbuilding under permitted development- all government and local council guidelines seem very vague with under 20m2 being ok, but 20m2-30m2 "probably ok".

The focus seems to be on maximum height and no more than 50pc of existing garden. If I'm looking to build a 7x4m timber framed workshop do I need permission?

Apologies if this has been answered elsewhere I couldn't find it!
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By MikeG.
It's not vague. "50% of the original land around the house" is very clear. You want to build 28 sq metres, so if you have more than 56 sq m of land around your house, you don't live in a National Park, AOB or World heritage Site, and if your permitted development rights haven't been previously removed, then you can build that (footprint) size without Planning Permission, so long as you then follow the further restrictions on eaves and ridge height, and location (back garden......but it's more complicated than that).

If you keep the building away from the boundary, you also won't need Building Regs approval (and by the way, you could go up to 30 sq metres internally without troubling the Building Inspector).
By Hobbo
Thanks MikeG. I've read elsewhere and seen on Youtube that if I build next to the boundary (and I've got a typical UK garden so is difficult not to) and if I go over 15m2 I don't need to involve building control as long as it is 'not substantially made of combustible material'. Wood being a bit burny means although I'm under the 50% of original land and under 30m2- I'll still need to involve building control?

That's my confusion- planning portal is clear about height, square metres, percentage of original land, but seems vague around this point- I can't find a definitive answer.

I also don't understand why I can't have a veranda?! I'm planning to have a workshop with a really big overhang, sort of like a covered area sheltered from the sun and rain, definitely not a veranda.. ;-) has anyone got any advice on whether building control ever has an issue with a workshop having a veranda?
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By MikeG.
The reason for your confusion is that you are mixing up 2 entirely different elements.....Planning Permission and Building Control.

Planning Permission (your permitted development rights) is as I's about the size and height you can build without permission. WHAT you are allowed to build.

Building Control is about how you build your building. Different regime, different people, different rules. It is these people who are interested in whether your building will burn down and threaten the neighbouring property. If you keep 1 metre away from the boundary and under 30 square metres, then there are no building regs implications (other than the normal electrical safety ones). If your out building is under 15 sq m then there are no circumstances in which Building Control comes into play. If it is between 15 and 30 sq m, which is what yours is, then it is exempt from regs if more than a metre from the boundary, or, if it closer to the boundary than that, it is of non-combustible construction. (This latter point is almost always interpreted as "that wall closest to the boundary must be non-combustible, the rest can be anything you like", although sometimes it is "anything within a metre of the boundary must be substantially non-combustible, the rest can be made of anything you like").

If you still aren't clear, then why not post a quick sketch of what you are proposing, including your boundaries.
By Hobbo
Ah, that makes sense. Ideally I'm looking to avoid building control, my previous experience with extensions ranged from really helpful to seemingly going out of their way to be bloody minded.

That also makes sense why some people are talking about building 2 separate outbuildings of 15m2 which I'm starting to prefer the idea of. Thanks for your patience!
By Hobbo
Right, final questions on permitted development..

Can you sanity check my understanding here? If I wanted to build a workshop within 1m of my boundary, over 15m2 internal dimensions but under 30m2, with maximum height overall of 2.5m, and as long as I haven't gone over the 50pc rule- I can do this without involving BC as long as the party wall is 'substantially non-combustible'?

If the party wall is timber framed, clad in metal sheathing (same material as I'm planning for the roof), with rockwool or similar insulation and plasterboard instead of osb- would that count as non-combustible? Block or brick isn't an option for me unfortunately.
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By MikeG.
Yes, to all that, except it is only the outer face of the wall which needs to be non-combustible. You don't need plasterboard internally. Be a bit careful with "metal", because my understanding (and this isn't my field) is that aluminium can be thought of as combustible whereas steel isn't. I would check with the supplier. There are alternatives, such as cementitious boards (Eternit is one such) which mimic timber feather edge boarding, and are non-combustible. I think they're pretty cheap, too. The "substantially" part of the non-combustible phrase means that such items as gutters and rafter feet or fascias are generally excluded from the requirement.

The only other thing regarding BR you need to comply with is electrical safety, which will need testing and certificating by an electrician.
By treeturner123

Just a note that, since the Grenfell Tower fire, Building Control departments have tightened up their view on fire resistance to buildings close to a boundary.

My experience with sheds is that they need to know that there is no means by which a fire can spread from inside the shed outwards so either the inner panels need to be shown, via manufacturer's details, to be fire resistant, or the external envelope does.

By Hobbo
Thanks Phil, just to be safe I think I'll go for belt and braces- steel cladding (roof sheets), fire retardant Insulation panels and plasterboard internally.
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By Baja-king
Have a look at Cedral Cladding

It's A rated for fire suppression, I used it on my Garden workshop build (20m2)
I wasn't required to fireproof anything else...


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By MikeG.
Baja-king wrote:Have a look at Cedral Cladding........

Yep, that's one of a multitude of cementitious boards, which I mentioned previously:

MikeG. wrote:......... There are alternatives, such as cementitious boards (Eternit is one such) which mimic timber feather edge boarding, and are non-combustible........