Old concrete sectional building, roof conversion apex to flat.

[Chris Bacon]

I came by an old concrete double garage, which had an apex roof, and I want to convert it to a flat roof.

Unfortunately, 2.5m max height applies.

I had thought it would be a good idea to cut the existing trusses (a couple are leaning against the wall, made of ~38mm equal angle, with ~27mm equal angle racing), and re-weld them together so that the top edges are in line, i.e. "flat" rather than apex, then cut the ends and weld on 40mm equal angle "legs". All equal angle thicknesses are ~3mm.

The 40mm angle legs would bolt into the vertical concrete posts of th sectional building.There would be a new 30mm equal angle tie, which could also support an insulated ceiling, to stiffen each truss.

Some 50 x 150 boards would also bolt to the 40mm "legs", with firring strips 150mm to 50mm or thereabouts to give some drop over the length.

External dimensions: 5000 wide, 6000 long. Span of truss approx 4800.

Look OK, or if not, why?

[Fredxx]

Your new trusses would be slightly longer, they would have to be modified to match the positions of your concrete posts. Otherwise looks a plan though the span feels very long. There is probably no need for the additional angle if the original span is unchanged.

I presume you're worried about your neighbours and the need for planning permission. Why not erect as is, with the fallback of making flat if the need comes?

[GB]

Erect it in a small hollow? :)

[Fredxx]

Reminds me of someone nearby who built an industrial property. He was limited by height, thereby forcing the ground level to be, well ground level.

Within 3 years he had been flooded by a local brook, for the sake of

300mm, as per local planning stipulations, he would have been well clear.

[Chris Bacon]

On 11/05/2021 17:27, Fredxx wrote: > On 11/05/2021 16:32, Chris Bacon wrote: >> I came by an old concrete double garage, which had an apex roof, and I >> want to convert it to a flat roof. >

Thanks for the reply. Yes, "flattening" the existing trusses would give ne ~5,000 mm rather than the ~4800 required, so I'd probably trim the inner ends more than the outer, deeper ends, and weld on 40mm x 40mm x

3mm "lehs" about 500 long on average (taking into account the roof's fall, and the ~250mm of leg that would be attached to the posts).

The existing trusses have a piece of 25mm x 3mm flat bar as a tie, which wouldn't be quite so convenient for attaching a ceiling. I could perhaps adjust the fixing position of the flat bar to save money on buying 30mm angle, and suspend battens...

Yes, I think the neighbours will kick up a stink. The total height, leaving things as they are, would be about 2700. As things are now, the ends of the trusses would also encroach on the vertical space available (~2,000mm) inside, at the edges, so I like the idea of "flat" for that reason too.

Being "tight", I don't want to have to re-do the job. There's the "loophole" that planning says that the height is measaured from the highest adjacent piece of ground, and I've dug out the slope the building's on by about 200mm, which would help, but the council's planning people are extremely unhelpful about what would comply with the rules, and suggest that I piut the thing up, and they wi;ll send someone to see about it when a complaint is made! Argh! Grr!

[Chris Bacon]

I've already dug out at one end (the adjacent ground on the higher ground level end is the one that planning should use, although the chap I spoke to at planning was initially unaware of this), BUT it only gives me about 225mm of "extra", and I need more like 400 for that to work...

So, as I ain't intending to dig up the reinforced pad I laid, having mixed the concrete in my Aldi mixer, about 5 cu metres of it, the roof must comply!

[GB]

Fit the existing trusses a bit lower.

And bend your knees, if you are tall?

[Tricky Dicky]

I would use the existing trusses your neighbour is highly unlikely to know all the rules regarding permitted development. If someone makes an issue about it, just apply for retrospective planning permission which is the way things are done round here and for some right old monstrosities to boot so a few centimetres of excess height is not going to be an issue.

Richard

[Fredxx]

My thoughts.

And the longer it takes for someone to complain, the less likely planning will get you to lower the roofline.

[Chris Hogg]

Is this a planning constraint imposed by the local authority, or a restrictive covenant imposed by a previous site owner (or even just hearsay)? It makes a difference and is worth finding out for certain. If the former, AIUI the council can take action to enforce it, assuming they become aware of the infringement and think it worth bothering about. If the latter, then AIUI it's up to the original owner or possibly a neighbour to enforce it through the civil courts, but either will cost them money in the first instance, which is something of a deterrent to that action.

[Chris Bacon]

On 12/05/2021 07:04, Chris Hogg wrote: > On Tue, 11 May 2021 16:32:14 +0100, Chris Bacon > [e-mail] wrote: >

It's planning.

There is useful information at:

(general, interactive, useful but not exhaustive) (sheds, playhouses, greenhouses, general garden buildings and structures) (permitted development rights)

[Brian Gaff (Sofa]

There do seem to be quite a lot of planning applications where the max height if only slightly over is allowed due to the existing structure, so might be an idea to run it by planning anyway. Brian

[Andrew]

I thought you were allowed outbuildings up to 4 metres high ?.

[Chris Bacon]

There are various constraints if it's to be "permitted development". One is n0t more than 30 sq m floor area inside. Another is not more than

2.5m high IF within 2m of a boundary, which this is. 4m would be lovely. But.

[Tricky Dicky]

If it exceeds 30 sq m it can still be erected under permitted development but you have to conform to building regulations.

Richard

[Roger Hayter]

Does that apply if any part of the building is within 2m of the boundary, or is it simply that no part of the building within two meters of the boundary can exceed 2.5m? Obviously a very different constraint!