Bi Fold doors under timber frame gable panel

6 May 2021
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United Kingdom
Hi all

Can't get a definitive answer from truss supplier, bi-fold installer or architect (unbelievably!!).

I'm building a bungalow extension with block walls up to the wall plate and a 4.5m opening in the gable end for bi-fold doors. The last truss on the gable end is spec'd as a timber frame panel i.e. ply faced. There is, therefore, no need for a lintel/steel as the timber replaces the need for block work above.

However, I obviously need to close the gap between the top of the bi fold frame and the underside of the truss. The bi-folds are not weight bearing/reliant on above but need to be fixed. Has anyone installed bi-folds with this setup as opposed to a traditional steel beam?

If so, what size/type of timber can be attached and dropped down from the truss that will neither deflect nor sag. Should it have a bearing on the block work either side of the opening e.g. 150mm on each side (4.8m overall length).

Also, should the timber be integral to the truss or can a solution be designed retrospectively i.e. once the truss is installed. To confirm, the timber that will be used will not be weight bearing - it will act only to close the gap and allow a fixing for the door frame and will be fixed to the truss.

Thanks in advance!
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Build a box lintel/timber infill and fit the sheathing over this and the truss.

I'd suggest a double truss if it is acting as the frame.
Thanks Woody

Yeah the gable frame is a double truss.

Do you mind just clarifying this option for me - I'm not sure whether I just need to fix a timber infill to the underside of the truss for the frame to be fixed to or utilise a bearing on the block work on either side of the bi folds. A box lintel would suggest a bearing?

I had already thought about fixing ply to the infill as well as the truss to act as bracing and for a flush surface for final finishing.

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Yes a box beam would have a bearing like any lintel, but would only be suitable if its either internal, or if it and especially the bearings, can be protected from damp.

There would be the issue of how the wall is finished between the door head and the truss

There may always be a bit of movement or flex in any roof and any timber frame gable, so additional strapping may be required, alternatively sheathing either side may deal with this.

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