Tony K

The arrangement you describe would be permitted development if the excavation was undertaken specifically for, and as a part of, the provision of the outbuilding. If the excavation and retaining wall was there already then the council were correct. As you found, setting the building into the ground (even if the excavation was preexisting) does of course increase your chance of getting planning permission, should you need it.

That's the way to do it. Even if you want to take a punt and build something without planning permission (and which you know requires it), build something sensible and considerate. That will significantly reduce the risk of a neighbour reporting you to the council, and significantly increase the chances of getting permission retrospectively if they do. That said, what you describe doesn't obviously exceed permitted development limits.

Be careful @Marko. A letter means nothing, if you want proper confirmation that your outbuilding does not require planning permission then you should apply for a certificate of lawfulness, anything less is simply an informal opinion and subject to change. As others have said, if the building is within two metres of any boundary and if the building is (or in your case will become) more than 2.5m tall in relation to external ground level then planning permission is absolutely required. Whether you would be applying for the extra height or for the whole building doesn't really matter, it's the same thing either way. Fun fact, if the ground on which your outbuilding is located is sloped or undulating then you get the benefit of measuring from the highest point. This can mean creating a part-excavated building (as others have mentioned) if you need more head height than would be achieved with a standard 2.5m building on flat ground, but can also mean that should there happen to have been a tall spot of ground within the footprint of your outbuilding before you built it, your building can be up to 2.5m from the top of that tall spot. Which is now hidden below your building, or removed as part of the provision of the building. Should the local planning authority, who must must have evidence of a breach of planning control to take enforcement action but who cannot ask you to remove the building to expose the original high spot (should it still exist) ultimately decide that, contrary to their informal advice, your building does require planning permission then I wouldn't mind betting that your land was uneven, and higher in the middle of the footprint than around the edges. Now that I come to think about it, I reckon the distance from the top of the highest point of the land the building now sits on to the top of the building, even with the extra roof height, was actually no greater than 2.5m. Wasn't it?

Is this to scale? 😂 Seriously, would a plasterer be happy to form a flush corner with the set up you show?

Got it, ta. But when you put board across the studs in the centre of the photo to form an external corner, will you be happy using tapered edge boards? Some people say it makes it harder to fit the corner bead if you've used tapered boards.

@nodare you using a stud to form the top of the external corner there, rather than carrying your top, horizontal plasterboard all the way across to meet your plasterboard on the far right?

Evening. I've got my internal partition walls frames up, and will begin to add plasterboard soon. Will I be able to form an external corner with tapered edge boards, or should either I cut the boards to create a full edge, or buy boards without a taper for the purpose of forming the corner? Cheers!

But they will be on the inside of the lining, and so make no difference to the size of the opening in the wall, surely? I'm working on the basis that the door lining kit marks the outside edge of the opening in the wall, and that I ought to butt the metal studs up to the lining then fix in place. I've bought a standard door lining kit and will see how it goes!

70mm.

@nod I'm thinking of buying some of these standard door lining kits, then build my metal stud wall frame tight around them in situ... https://www.diy.com/departments/door-frame-set-2021mm-94mm/1451651_BQ.prd In your experience, is that OK and do I need a timber inside the metal stud next to the door lining?

As you say, the opening isn't structural exactly, that just seems to be the term most commonly used for the hole in an internal wall where a door will one day go. I don't need to worry about deflection, the frame itself accounts for that (not that I'll have much). I want to complete the metal stud walls and also plasterboard one side of the walls (all internal), ideally just leaving openings where the bedroom doors will later go. My instinct is to take the size of a door, add 40mm to both sides and the top and create an opening of that subsequent size.

Evening I've seen various guides on this topic, and they seem to differ regarding the critical dimensions! I'm using metal stud walls internally. How much larger than the actual door should I make the hole in the wall?! Alternatively, should I buy a standard door lining set, construct it and build the frame up to (and attached to) that? Cheers

The benefit of the plugs is that I can unscrew them, which might be necessary either because I make a mistake during installation, or to move an internal wall in future. I can imagine the gun would be a lot quicker, but the nails are more permanent.

Cheers. I'll probably go with the nailable plugs as thats what the metal stud supplier recommends. Just thought I'd ask because sometimes you learn after the event that the recommend method isn't the best way!

Evening. I'm installing metal stud frame internal partition walls soon. The supplier recommends nailable plugs for fixing the metal floor track to my concrete floor. For no particular reason, I've just never used nailable plugs before. I get the gist, I drill a hole the correct width and depth through the floor track into the concrete below, push the plug into the gap, then hammer it home. They just don't seem as reliable as drilling a hole, putting a plug in, then screwing the track in place. Has anyone got any strong views on what fixing to use?!

It is the latter, so 12.5mm plasterboard on both sides with the additional soundboard on one side

For those with an interest, I spoke to a soundproofing firm who were quite approachable and realistic. They offered me a design achieving 61db at 160mm thick, which I just don't have the space to do. In conversation they suggested a standard wall comprising 70mm metal frame, 50mm acoustic insulation inside, 12.5mm plasterboard on either side and then, finally, the addition of this stuff to one side of the wall only: https://soundproofingstore.uk/product/prosound-soundboard-4-stud-walls/ Total wall thickness 125mm.

Amen to that!

I have to say my instinct was the same. Interesting that it's been fine for you. I presume you have the standard domestic noise levels etc (kids, dog, wife... 😉)?

That'll be quite a thick wall wouldn't it?

What overall wall thickness is your design @Mike?

Did you establish (either before, after or both) a dB level for that arrangement?

I am using metal stud walls (70mm studs) for all internal partition walls, most commonly between bedrooms and bathrooms. The various metal stud wall suppliers offer different details and configurations that can be achieved using their products (different ways to build internal partition walls, basically). Each option has a stated sound rating. Presuming I want to stay around 100 - 130mm total wall thickness, my options seem to range from 34-63 RwdB (e.g British Gypsum GypWall Single Frame) to 61-65 RwdB (e.g GypWall Resilient). Building Regs require 40/45db, which I understand is (firstly) likely to be achieved by a basic frame with insulation in the void and (secondly) not an especially high level of noise insulation. Within my wall width-limit I can see a few options that get me up to 60-65 db though, of course, the cost goes up. I understand the basic principles involved and can probably create a wall of my own design using cheap studs, decent insulation, a gap, and some combination of acoustic and/or standard plasterboard. I would be interested to know... 1. In reality, how much difference would I actually notice between a 40-45 db wall and a 60-65? We have very small bedrooms in a terraced layout and we want a nice, quiet house so I don't mind the extra cost, but I don;t want to waste time and money if the benefits are negligible. 2. Does anyone have any good tips for creating a good (and reasonably priced) internal metal stud wall with high sound insulation qualities? I am thinking perhaps a 70mm stud, 50mm insulation, a 15mm airgap on one side of the insulation, standard plasterboard on one side of the wall and double skin on the other, but if anyone has a better recipe then please do share! Cheers

Cheers @nod I will.

Thanks @nod. Am I right to think I can mix and match between different makes, so long as the sizings are the same?