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

https://i.ibb.co/2jgk4gY/DSC00126.jpg

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.

https://i.ibb.co/XtC5YWJ/DSC00128.jpg

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?

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.

https://i.ibb.co/2jgk4gY/DSC00126.jpg

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.

https://i.ibb.co/XtC5YWJ/DSC00128.jpg

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?

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?

On 11/05/2021 17:27, Fredxx wrote:

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?



Erect it in a small hollow?

On 11/05/2021 17:42, GB wrote:
On 11/05/2021 17:27, Fredxx wrote:

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?

Erect it in a small hollow?

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.

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.

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?

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!

On 11/05/2021 17:42, GB wrote:
On 11/05/2021 17:27, Fredxx wrote:
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?

Erect it in a small hollow?


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!

On 11/05/2021 18:14, Chris Bacon wrote:
On 11/05/2021 17:42, GB wrote:
On 11/05/2021 17:27, Fredxx wrote:
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?

Erect it in a small hollow?


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!


Fit the existing trusses a bit lower.

And bend your knees, if you are tall?

On Tuesday, May 11, 2021 at 6:18:56 PM UTC+1, GB wrote:
On 11/05/2021 18:14, Chris Bacon wrote:
On 11/05/2021 17:42, GB wrote:
On 11/05/2021 17:27, Fredxx wrote:
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?

Erect it in a small hollow?


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!

Fit the existing trusses a bit lower.

And bend your knees, if you are tall?

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

On 11/05/2021 21:32, Tricky Dicky wrote:
On Tuesday, May 11, 2021 at 6:18:56 PM UTC+1, GB wrote:
On 11/05/2021 18:14, Chris Bacon wrote:
On 11/05/2021 17:42, GB wrote:
On 11/05/2021 17:27, Fredxx wrote:
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?

Erect it in a small hollow?


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!

Fit the existing trusses a bit lower.

And bend your knees, if you are tall?

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.

My thoughts.

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

On 12/05/2021 07:04, Chris Hogg wrote:
On Tue, 11 May 2021 16:32:14 +0100, 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.

https://i.ibb.co/2jgk4gY/DSC00126.jpg

Unfortunately, 2.5m max height applied.

Is this a planning constraint imposed by the local authority, or a
restrictive covenant imposed by a previous site owner...

It's planning.

There is useful information at:

https://interactive.planningportal.co.uk/ (general, interactive, useful
but not exhaustive)
https://www.planningportal.co.uk/inf...3/outbuildings
(sheds, playhouses, greenhouses, general garden buildings and structures)
https://www.gov.uk/government/public...nical-guidance
(permitted development rights)

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

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Fredxx" wrote in message
...
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.

https://i.ibb.co/2jgk4gY/DSC00126.jpg

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.

https://i.ibb.co/XtC5YWJ/DSC00128.jpg

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?

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?

On 11/05/2021 18:14, Chris Bacon wrote:
On 11/05/2021 17:42, GB wrote:
On 11/05/2021 17:27, Fredxx wrote:
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?

Erect it in a small hollow?


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!


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

On 15/05/2021 15:34, Andrew wrote:

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

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.

On Saturday, May 15, 2021 at 6:17:39 PM UTC+1, Chris Bacon wrote:
On 15/05/2021 15:34, Andrew wrote:

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

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

Richard

On 15 May 2021 at 18:17:36 BST, "Chris Bacon"
wrote:

On 15/05/2021 15:34, Andrew wrote:

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

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.

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!

--
Roger Hayter