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StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7137
Experience:  Structural Engineer
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, i need some professional advice probably from a

Resolved Question:

hi, i need some professional advice probably from a structural eng. on some home improvements. i had the bungalow built in 1999, scotland, uk. the whole area within the bungalow was open before the stud partitions were erected so there are no structural walls. however, my concern is that i have a lot of junk in the loft now and i am making the kitchen area open plan therefore what support (and method of support) if any should be in place of the partitions i am removing? i am assuming i do not need planning permission to remove these partitions. the span of the W style trusses above the kitchen area is 7 m and the trusses measure 71 mm x 35 mm.

Submitted: 2 years ago.
Category: Structural Engineering
Expert:  StructuralEng replied 2 years ago.
StructuralEng : Are they premanufacrured trusses with metal plates connecting the members?
Customer:

there are thin mitek plates and yes the trusses were pre-manufactured before delivery to site. not sure of the exact history though

StructuralEng :

These type of premanufactured trusses generally only want and are designed for two bearing points.

StructuralEng :

The loft you refer to is the bottom chord of the trusses?

Customer:

not sure what you mean there?

StructuralEng :

Which part?

Customer:

bottom chord of the trusses?

StructuralEng :

The bottom chord of the truss is the flat portion that makes up the bottom of the truss.

Customer:

ok, yes we are talking about the space below the top of the W down to the bottom of the trusses

StructuralEng :

Was that designed as living space?

Customer:

ok, yes we are talking about the space from the top of the W down to the bottom of the trusses

StructuralEng :

I would not add supports to the truss that it was not intended to have. This can cause members designed as tension members to have stress reversal and go into compression. This is something that should be avoided. It can cause instability.

Customer:

this was only ever meant to be loft space due to the design of the trusses

StructuralEng :

A loft is living space, correct?

Customer:

i guess it could be if converted?

Customer:

i have flat board up there at the moment for storage of general junk...

StructuralEng :

ok. I would limit the load up there to 20 psf.

Customer:

ok, 20 psf is that max.?

StructuralEng :

and not add any supports. You do not want to add supports to a truss

StructuralEng :

Yes, 20 psf is the design load for a storage attic (loft)

Customer:

ok, i can check the loading. i understand what you are saying about the trusses being in compression so what alternative is there?

StructuralEng :

The only two options are to limit the load on the trusses to the design load or to reinforce the trusses (or loft area) to support the load you desire

Customer:

ok, how can i re-inforce the trusses? and i take it this will require planning permission?

StructuralEng :

It will require permission.

StructuralEng :

Do you want to know generally what is done to reinforce or exactly what you need to do to reinforce your specific trusses.

Customer:

in general for now if that's ok

StructuralEng :

It generally requires adding wood to most, if not all, members of the truss and reinforcing the connections with wood gussets

Customer:

ok, i see. i am glad i have spoken with you on this. i will check the loading before removing further junk if nec. and then use another loft space if required

Customer:

just to confirm, when you say 20 psf, is that for flooring / junk?

StructuralEng :

That is for the junk. The dead load (flooring) is separate

Customer:

it is not floored at the moment

Customer:

or rather wasn't when the house was built

Customer:

so should i take that into account?

StructuralEng :

No

Customer:

ok. very good and thank you! i appreciate the help and look forward to talking to you again later about sthing else

StructuralEng :

No problem. I'm happy to help.

StructuralEng :

Good luck with your project

StructuralEng :

I look forward to talking with you about any additional issues you have.

Customer:

thank you

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