Loft conversion

[burts]

Have a question in regards to a loft conversion with a truss roof.

Instead of steels being installed length ways between gable ends, then joists between them and supporting the roof (I think this is the normal way?)

Why can’t timber joists just span the 2 outside walls and the roof be supported off them? Is the weight still not being supported by load bearing walls?

I’m just curious about this, I have no knowledge of it and will be getting an SE

 

[^woody^]

Because they will stick out the roof

 

[burts]

Because they will stick out the roof

As in the depth of the joist is bigger than the gap between inner leaf and roof tile .... wouldn’t that depend on the roof pitch ? Or am I missing the point

I had one loft guy round and suggested steels running width ways as length ways will impede stair location

 

[johnny2007]

A structural engineer will tell you what to do.
You will need their calculations in any case, so no point speculating.

 

[tony1851]

Because they will stick out the roof

They don't need to stick out of the roof; depending on the section-size, they can be chamfered at the bearings.

 

[burts]

A structural engineer will tell you what to do.
You will need their calculations in any case, so no point speculating.

Johnny with all due respect, I’m a tradesman and take interest in knowing what needs to happen and gaining knowledge in areas of the building game I don’t know about.

Everyone here knows I need a SE and building control involved, so I’m not about to start getting in my loft and working on a whim.

Not sure why people bother to comment telling others not to worry because you need a structural engineer. I like to know so i can make my own judgement as to whether that professional I employ is knowledgeable

 

[johnny2007]

Johnny with all due respect, I’m a tradesman and take interest in knowing what needs to happen and gaining knowledge in areas of the building game I don’t know about.

Everyone here knows I need a SE and building control involved, so I’m not about to start getting in my loft and working on a whim.

Not sure why people bother to comment telling others not to worry because you need a structural engineer. I like to know so i can make my own judgement as to whether that professional I employ is knowledgeable

The fact is that you can't make plans unless you know how the structure is going to stay up.
And to do that you can't get good advice from anyone else rather than a structural engineer.
As you're going to employ them anyway, why not do so now and avoid losing sleep over something that they'll be able to do for you and you have to pay at one point anyway.?
As

 

[burts]

Johnny with all due respect, I’m a tradesman and take interest in knowing what needs to happen and gaining knowledge in areas of the building game I don’t know about.

Everyone here knows I need a SE and building control involved, so I’m not about to start getting in my loft and working on a whim.

Not sure why people bother to comment telling others not to worry because you need a structural engineer.

The fact is that you can't make plans unless you know how the structure is going to stay up.
And to do that you can't get good advice from anyone else rather than a structural engineer.
As you're going to employ them anyway, why not do so now and avoid losing sleep over something that they'll be able to do for you and you have to pay at one point anyway.?
As

Simply asking why timbers spanning the width isn’t the same in terms of strength as steels spanning the length with timbers in between them. Both ways the weight bears on the walls.

I’m not loosing no sleep, and it’s good to have ideas in your head cos not all SE have the same opinions as I found out for my rear extension when some told me I need at least 8 piles, 12 piles ..... and because I done some research I ended up with 4 and about 6k saved

 

[wessex101]

This is quite a clever system for loft conversions with trussed rafters ......... https://www.telebeam.co.uk/

It also shows the chamfer required at the roof eaves.

 

[^woody^]

They don't need to stick out of the roof; depending on the section-size, they can be chamfered at the bearings.

Just like they don't need to span front to back and create problems that don't need to exist

 

[tony1851]

You've lost me.......

 

[^woody^]

You've lost me.......

Design should be simple. Why span front to back and have deeper beams, floors higher than they need be and chamfered webs when there is no need? And then what happens with the rafter support across the loft - another beam? Do you have shares in the steel industry, the bigger and more beams the merrier?

 

[tony1851]

Design should be simple. Why span front to back and have deeper beams, floors higher than they need be and chamfered webs when there is no need? And then what happens with the rafter support across the loft - another beam? Do you have shares in the steel industry, the bigger and more beams the merrier?

Depends where the load-bearing walls are.
I'd be surprised if there isn't at least one on the 1st floor, but then again I might be wrong?

 

[^woody^]

Depends where the load-bearing walls are.

Depends if the client is happy for his floor to be dug up to prove the internal wall foundations.

It sounds like you routinely design front-to-back beams, with all these "arh but" comments.

 

[tony1851]

Depends if the client is happy for his floor to be dug up to prove the internal wall foundations.

It sounds like you routinely design front-to-back beams, with all these "arh but" comments.

No I don't. Usual practice is to have two steels at floor level gable-to-gable to support the floor.
I was simply making the point that if floor joists are run front-to-back (which can be the case if there is a middle wall) they can be chamfered at the eaves.
They don't need the full depth at the bearing because, as you know, the only issue is the shear stress which is 3Fv/2A but of course you don't need me to tell you that......