Riverside Cottage 5
 

One for the structural engineers...

The architect has specified manufactured dormer trusses. When I asked
him to supply a drawing for the manufacturers, showing the two studwork
partition walls which are below the new timber (90deg. roughly midway),
he said it was not necessary as they are not load bearing.

Now I was only ever electrical but they still made us do applied
mechanics. A simple beam carrying a load has to deflect whether the load
is distributed or not. Any deflection must cause some of the load to be
carried by the walls below?
--
Tim Lamb

Riverside Cottage 5
 

On Saturday, 23 July 2016 15:50:59 UTC+1, Tim Lamb wrote:
One for the structural engineers...

The architect has specified manufactured dormer trusses. When I asked
him to supply a drawing for the manufacturers, showing the two studwork
partition walls which are below the new timber (90deg. roughly midway),
he said it was not necessary as they are not load bearing.

Now I was only ever electrical but they still made us do applied
mechanics. A simple beam carrying a load has to deflect whether the load
is distributed or not. Any deflection must cause some of the load to be
carried by the walls below?

Unless the roof is tiled before the studding is installed.

The trusses are made to standard size/spans, ie no allowance is made for any additional support.
If the roof is heavier, they put them closer together.

Riverside Cottage 5
 

In message ,
harry writes
On Saturday, 23 July 2016 15:50:59 UTC+1, Tim Lamb wrote:
One for the structural engineers...

The architect has specified manufactured dormer trusses. When I asked
him to supply a drawing for the manufacturers, showing the two studwork
partition walls which are below the new timber (90deg. roughly midway),
he said it was not necessary as they are not load bearing.

Now I was only ever electrical but they still made us do applied
mechanics. A simple beam carrying a load has to deflect whether the load
is distributed or not. Any deflection must cause some of the load to be
carried by the walls below?

Unless the roof is tiled before the studding is installed.

The trusses are made to standard size/spans, ie no allowance is made
for any additional support.
If the roof is heavier, they put them closer together.

This is domestic loading (bedroom/bathroom). I vaguely assumed they
might reduce the floor joist thickness because of the additional
support.

--
Tim Lamb

Riverside Cottage 5
 

On 7/23/2016 3:50 PM, Tim Lamb wrote:
One for the structural engineers...

The architect has specified manufactured dormer trusses. When I asked
him to supply a drawing for the manufacturers, showing the two studwork
partition walls which are below the new timber (90deg. roughly midway),
he said it was not necessary as they are not load bearing.

Now I was only ever electrical but they still made us do applied
mechanics. A simple beam carrying a load has to deflect whether the load
is distributed or not. Any deflection must cause some of the load to be
carried by the walls below?

That must be correct, unless the walls below are not fully in contact
with the truss, or at least not taking much weight. As Harry says, one
way to achieve that is to fully load the truss before building the
studwork partition walls. I suppose the real question is what's under
the partition walls, and can that take part of the roof load?

Houses are generally built with so much reserve strength that you can
get away with all sorts of mess-ups like this.

Riverside Cottage 5
 

In message , GB
writes
On 7/23/2016 3:50 PM, Tim Lamb wrote:
One for the structural engineers...

The architect has specified manufactured dormer trusses. When I asked
him to supply a drawing for the manufacturers, showing the two studwork
partition walls which are below the new timber (90deg. roughly midway),
he said it was not necessary as they are not load bearing.

Now I was only ever electrical but they still made us do applied
mechanics. A simple beam carrying a load has to deflect whether the load
is distributed or not. Any deflection must cause some of the load to be
carried by the walls below?

That must be correct, unless the walls below are not fully in contact
with the truss, or at least not taking much weight. As Harry says, one
way to achieve that is to fully load the truss before building the
studwork partition walls. I suppose the real question is what's under
the partition walls, and can that take part of the roof load?

Surely the roof load is carried by the outer walls and simply
stretches/spreads the floor component.

Houses are generally built with so much reserve strength that you can
get away with all sorts of mess-ups like this.

It is a bit academic anyway as the thickness turns out to be the same as
was used when the rest of the house was build in 1995.



--
Tim Lamb

Riverside Cottage 5
 

Tim Lamb wrote:
One for the structural engineers...

The architect has specified manufactured dormer trusses. When I asked
him to supply a drawing for the manufacturers, showing the two
studwork partition walls which are below the new timber (90deg.
roughly midway), he said it was not necessary as they are not load
bearing.
Now I was only ever electrical but they still made us do applied
mechanics. A simple beam carrying a load has to deflect whether the
load is distributed or not. Any deflection must cause some of the
load to be carried by the walls below?

Nope, it's all carried by the exterior walls, including the pre-calculated
deflection.
When we put trusses up on newbuild houses (big 5 or 6 bedroom houses) they
go on before any internal walls, or even floors are in place.

The truss manufacturers will build them based on the measurements of the
exterior walls and what's going on top, tiles, slates etc

Riverside Cottage 5
 

In message , Phil L
writes
Tim Lamb wrote:
One for the structural engineers...

The architect has specified manufactured dormer trusses. When I asked
him to supply a drawing for the manufacturers, showing the two
studwork partition walls which are below the new timber (90deg.
roughly midway), he said it was not necessary as they are not load
bearing.
Now I was only ever electrical but they still made us do applied
mechanics. A simple beam carrying a load has to deflect whether the
load is distributed or not. Any deflection must cause some of the
load to be carried by the walls below?

Nope, it's all carried by the exterior walls, including the pre-calculated
deflection.
When we put trusses up on newbuild houses (big 5 or 6 bedroom houses) they
go on before any internal walls, or even floors are in place.

The truss manufacturers will build them based on the measurements of the
exterior walls and what's going on top, tiles, slates etc

This is chalet bungalow, Phil. The roof load goes on the outside walls
no question. I wondered why they ignored existing internal partition
walls when considering sizing the tie/joist supporting the bedroom
floor.



--
Tim Lamb

Riverside Cottage 5
 

On 7/24/2016 7:25 PM, Tim Lamb wrote:
In message , Phil L
writes
Tim Lamb wrote:
One for the structural engineers...

The architect has specified manufactured dormer trusses. When I asked
him to supply a drawing for the manufacturers, showing the two
studwork partition walls which are below the new timber (90deg.
roughly midway), he said it was not necessary as they are not load
bearing.
Now I was only ever electrical but they still made us do applied
mechanics. A simple beam carrying a load has to deflect whether the
load is distributed or not. Any deflection must cause some of the
load to be carried by the walls below?

Nope, it's all carried by the exterior walls, including the
pre-calculated
deflection.
When we put trusses up on newbuild houses (big 5 or 6 bedroom houses)
they
go on before any internal walls, or even floors are in place.

The truss manufacturers will build them based on the measurements of the
exterior walls and what's going on top, tiles, slates etc

This is chalet bungalow, Phil. The roof load goes on the outside walls
no question. I wondered why they ignored existing internal partition
walls when considering sizing the tie/joist supporting the bedroom floor.



Because that would really complicate the calc, you would need to look at
what doors there were through the stud wall, for example. Easier to
assume that it isn't there. Obviously, the studs may take a bit of load
as the truss deflects, but a little bit of support mid-truss will be
very good at reducing the truss deflection. You don't need to worry
about the studs buckling. You are right that, in theory, you might get a
bit of bowing in any studs which are tight up against the bottom of the
truss. But it won't be significant (unless the build is really cocked up).

Riverside Cottage 5
 

On 7/24/2016 7:25 PM, Tim Lamb wrote:

This is chalet bungalow, Phil. The roof load goes on the outside walls
no question. I wondered why they ignored existing internal partition
walls when considering sizing the tie/joist supporting the bedroom floor.

I'd completely misunderstood before. I assumed these were first floor
partition walls, and you were worried about them taking part of the roof
load and transmitting that down on whatever the partition walls were
resting on.

If the tie/joist was undersized because it was resting on a partition
wall, what would happen when somebody decided to remove the wall? After
all, partition walls aren't supposed to be load bearing, so your
successor might decide to open things up a bit and go open plan.

Riverside Cottage 5
 

On Sunday, 24 July 2016 20:24:28 UTC+1, newshound wrote:

Obviously, the studs may take a bit of load
as the truss deflects, but a little bit of support mid-truss will be
very good at reducing the truss deflection. You don't need to worry
about the studs buckling. You are right that, in theory, you might get a
bit of bowing in any studs which are tight up against the bottom of the
truss. But it won't be significant (unless the build is really cocked up).

Your biggest problem will be if they lift the stud walls from the floors. I don't fully understand why that happens but I have heard of it happening.

Riverside Cottage 5
 

In message ,
Weatherlawyer writes
On Sunday, 24 July 2016 20:24:28 UTC+1, newshound wrote:

Obviously, the studs may take a bit of load
as the truss deflects, but a little bit of support mid-truss will be
very good at reducing the truss deflection. You don't need to worry
about the studs buckling. You are right that, in theory, you might get a
bit of bowing in any studs which are tight up against the bottom of the
truss. But it won't be significant (unless the build is really cocked up).

Your biggest problem will be if they lift the stud walls from the
floors. I don't fully understand why that happens but I have heard of
it happening.

OK All. I was just curious. Future proofing and ease of calculation
seems the most likely scenario.


--
Tim Lamb

Riverside Cottage 5
 

On 7/25/2016 7:14 AM, Weatherlawyer wrote:
On Sunday, 24 July 2016 20:24:28 UTC+1, newshound wrote:

Obviously, the studs may take a bit of load
as the truss deflects, but a little bit of support mid-truss will be
very good at reducing the truss deflection. You don't need to worry
about the studs buckling. You are right that, in theory, you might get a
bit of bowing in any studs which are tight up against the bottom of the
truss. But it won't be significant (unless the build is really cocked up).

Your biggest problem will be if they lift the stud walls from the floors. I don't fully understand why that happens but I have heard of it happening.


Perhaps from the studs shrinking after installation, particularly if
ordinary sawn timber rather than kiln dried?

Interesting to see in "Building Alaska" how allowance is made for
settlement / shrinkage of main wall logs by having "floating" window frames.

Riverside Cottage 5
 

On Monday, 25 July 2016 09:22:46 UTC+1, newshound wrote:
On 7/25/2016 7:14 AM, Weatherlawyer wrote:
On Sunday, 24 July 2016 20:24:28 UTC+1, newshound wrote:

Obviously, the studs may take a bit of load
as the truss deflects, but a little bit of support mid-truss will be
very good at reducing the truss deflection. You don't need to worry
about the studs buckling. You are right that, in theory, you might get a
bit of bowing in any studs which are tight up against the bottom of the
truss. But it won't be significant (unless the build is really cocked up).

Your biggest problem will be if they lift the stud walls from the floors. I don't fully understand why that happens but I have heard of it happening.


Perhaps from the studs shrinking after installation, particularly if
ordinary sawn timber rather than kiln dried?

Interesting to see in "Building Alaska" how allowance is made for
settlement / shrinkage of main wall logs by having "floating" window frames.

I should imagine such shrinkage is confined to summer when a fresh slap of mud and moss will compensate, or ant cracks in winter are self fullfilling filling when it snows.