Roof truss change.
 

For 5m span, front of concrete prefab. It was a simple king post truss
design, with the bottom of the king post also bolted via a bracket to a
vertical post netween the two sets of opening doors (1 pair each side)
where the word "then" in the pic. is.

The new truss reduces the height of the apex, as well as raising the
eaves height for headroom inside. It will probably also be fixed to a
vertical central post under to floor.

Rough sketch at: https://i.ibb.co/7JH1NHn/IMG-20210607-182851-1.jpg

Any ideas for new bracing? It's in 30mm by 30mm by 3mm equal angle.

Roof truss change.
 

On 07/06/2021 18:37, Chris Bacon wrote:

For 5m span, front of concrete prefab. It was a simple king post truss
design, with the bottom of the king post also bolted via a bracket to a
vertical post netween the two sets of opening doors (1 pair each side)
where the word "then" in the pic. is.

The new truss reduces the height of the apex, as well as raising the
eaves height for headroom inside. It will probably also be fixed to a
vertical central post under to floor.
Rough sketch at: https://i.ibb.co/7JH1NHn/IMG-20210607-182851-1.jpg

Any ideas for new bracing? It's in 30mm by 30mm by 3mm equal angle.

There is a prefab "low profile" truss design that adds extra height at
the eves and uses a shallower pitch to give less ridge height. That does
use a number of extra bracing members to achieve the stiffness. There is
a picture of one he

https://www.buildershoponline.co.uk/...design-48.html

(1st graphic, second row, 5 down)

An extra row of block on top of the wall might be another option...

--
Cheers,

John.

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| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
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Roof truss change.
 

On 08/06/2021 11:47, John Rumm wrote:
On 07/06/2021 18:37, Chris Bacon wrote:

For 5m span, front of concrete prefab. It was a simple king post truss
design, with the bottom of the king post also bolted via a bracket to
a vertical post netween the two sets of opening doors (1 pair each
side) where the word "then" in the pic. is.

The new truss reduces the height of the apex, as well as raising the
eaves height for headroom inside. It will probably also be fixed to a
vertical central post under to floor.
Rough sketch at: https://i.ibb.co/7JH1NHn/IMG-20210607-182851-1.jpg

Any ideas for new bracing? It's in 30mm by 30mm by 3mm equal angle.

There is a prefab "low profile" truss design that adds extra height at
the eves and uses a shallower pitch to give less ridge height. That does
use a number of extra bracing members to achieve the stiffness. There is
a picture of one he

https://www.buildershoponline.co.uk/...design-48.html

(1st graphic, second row, 5 down)

That looks very Howe-like. I now have a modified king-post/Howe design,
which I have tested empirically by dangling off it. I'll see if I can
post a picture somewhere.

An extra row of block on top of the wall might be another option...

Prefab concrete (sectional). Planning, costs are relevant.

Roof truss change.
 

On 08/06/2021 14:36, Chris Bacon wrote:
On 08/06/2021 11:47, John Rumm wrote:
On 07/06/2021 18:37, Chris Bacon wrote:

For 5m span, front of concrete prefab. It was a simple king post
truss design, with the bottom of the king post also bolted via a
bracket to a vertical post netween the two sets of opening doors (1
pair each side) where the word "then" in the pic. is.

The new truss reduces the height of the apex, as well as raising the
eaves height for headroom inside. It will probably also be fixed to a
vertical central post under to floor.
Rough sketch at: https://i.ibb.co/7JH1NHn/IMG-20210607-182851-1.jpg

Any ideas for new bracing? It's in 30mm by 30mm by 3mm equal angle.

There is a prefab "low profile" truss design that adds extra height at
the eves and uses a shallower pitch to give less ridge height. That
does use a number of extra bracing members to achieve the stiffness.
There is a picture of one he

https://www.buildershoponline.co.uk/...design-48.html

(1st graphic, second row, 5 down)

That looks very Howe-like. I now have a modified king-post/Howe design,
which I have tested empirically by dangling off it. I'll see if I can
post a picture somewhere.

You can post pictures on the wiki if you want... (drop me an email if
you need an account created)

An extra row of block on top of the wall might be another option...

Prefab concrete (sectional). Planning, costs are relevant.

If you are making it higher at the eves, I doubt it matters much how you
do it from a planning PoV. (and blocks are probably cheaper than timber
- although I understand the current wall thickness might be rather limited).


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Roof truss change.
 

On 08/06/2021 15:12, John Rumm wrote:
On 08/06/2021 14:36, Chris Bacon wrote:

I now have a modified king-post/Howe
design, which I have tested empirically by dangling off it. I'll see
if I can post a picture somewhere.

You can post pictures on the wiki if you want... (drop me an email if
you need an account created)

Not sure how, but:

https://i.ibb.co/12xkTKM/DSC00558.jpg (lifting into place)

https://i.ibb.co/FDHy0sg/DSC00568.jpg (in place)


An extra row of block on top of the wall might be another option...

Prefab concrete (sectional). Planning, costs are relevant.

If you are making it higher at the eves, I doubt it matters much how you
do it from a planning PoV. (and blocks are probably cheaper than timber
- although I understand the current wall thickness might be rather
limited).

The original trusses started at the top of the concrete sectional walls,
and reached 2670mm at the apex. I cut and re-worked them as shown. The
building would otherwise not be "permitted development" as it's only
750mm from the property boundary so must be 2500mm or lower. The maximum
height of the building is what matters (although it was cut into a
slight slope, so theoretically 2670mm measured from the highest adjacent
ground should have been OK. I called planning to discuss, the bloke had
no idea, and would not advise anyway. Useless.

Anyway, next hing is to finish off the trim above the concrete, fit the
two pairs of doors in the front, and buy Stirling board and box profile
plus odds and ends.