Replacing collared roof trusses

[Anonymous]

Hello all,

My parents are thinking of buying a cottage in which the roof space has been converted into bedrooms. The only problem is that there are three collared roof trusses at chest height, which restrict access to the bedrooms. What, if any, is the best way of removing / modifying at least two of these whilst still retaining the strength that they provide?

Thanks.

 

[Anonymous]

The reason why the collars (or tie beams?) have not been removed already is probably due to two main reasons:.

1) Listing or conservation restriction

2) Cost involved

If due to the first reason there is not very much you can do.
If cost is no major consideration, then anything can be done.

From your very brief description these collars appear to form a major structural restraining function to roof and side wall spread, removal of these, and more importantly the amount of tension they provide to the cottage, will determin wether you could "re-collar" the whole roof higher up towards the apex, or a more substantial purlin arrangement be constructed.
One thing is very certain, you would need expert advise before you can remove them.

IT is worth mentioning that a majority of old farm workers cottages which formed part of big estates, were demolished or collapsed due to the fact that they cut away collars and tie beams to create more bedrooms etc.. .

If you supply a bit more information on type of cottage construction you may get better help.

 

[Anonymous]

I agree with Middi. You should not under any circumstances consider removing any of the collars without first consulting a structural engineer. If the building is listed, you will also require LBC. And I'm not sure whether this modification would also require building regs consent (assuming the engineer OK's it). I suspect that it would.

 

[Anonymous]

A purlin could be introduced to take the place of a collard truss if it was adequately supported at each end.

As the others advise, get professional help.

Bryan

 

[Anonymous]

Thanks for your responses so far. A little more information about the house:

The cottage is stone, built in approximately 1820. The roof is 26 feet long and the span is approximately 18 feet to the outside of the walls.

The roof was completely rebuilt five years ago with slates, and felt underneath. The inside of the roof area has been insulated and lined with plasterboard, and the only members visible are the three rafters with the collars bolted to them. The collars are at approximately 42 inches above the floor level.

There is sufficient head height to the ridge beam to be able to put new short collars with the underside of these at 6 feet above the floor level. The floor in the roof area is on 9 inch x 2 inch joists which are exposed in the living area below.

Is it a possibility to have vertical posts up to the rafters and braced back to the rafters at floor level, and also bolted to top of floor joists? Also to have a collar at head-height below the ridge beam?