Extend Loft Conversion - Windbrace and extending flitch beam

Discussion in 'Builders' Talk' started by James Surrey, Sep 30, 2020.

  1. James Surrey

    James Surrey New Member

    Hi. I'd be grateful for anyone's technical advice....We had a loft conversion about 10years ago by a loft company but have since had a two-storey side extension built, which means we are easily able to reclaim the area where we used to have a hip roof (which is now within the new side extension roof). The original loft conversion steel beams, floor joists, floor are already in situ to the original external wall, but I need to make a couple of adjustments in terms of the studwork/walls to enable us to use this space as an ensuite:

    1) We have a flitch beam at the apex of the original roof, which was added when we converted. It is supported at one end by a stud wall which hides the chimney stack but this stud wall needs to be moved back closer to the chimney (there is a large gap) and the flitch beam will be about 300mm too short - could we have a U-shaped bracket made to support under and extend that end of the flitch by 300mm onto the new stud wall? Or alternatively would we need to weld a new piece of steel or bolt some timber extensions to the existing beam? Its not really feasible to replace the existing flitch beam and I suspect few welders will be keen to weld a flitch beam in situ in case the surrounding wood catches on fire?

    2) In the new roof area, we need to build a stud wall to divide the newly-reclaimed conversion from the new loft section (we can't convert it all due to lack of floor steels and wind-braces and angled purlin supports in situ). What I want to know is, is it ok to build the vertical windbrace beam / apex support and two of the purlin support beams into the dividing stud wall? I'm assuming that as long as I don't change the braces/supports in any way, adding studwork / plasterboard around them won't change their function?
    I'm going to get the building inspector out but I ideally wanted to erect these walls before they attend so that I can get the structure signed off in one go. Thanks for your help.
     
  2. stevie22

    stevie22 Screwfix Select

    You need an SE to sort this, you can't just make the beam longer
     
  3. James Surrey

    James Surrey New Member

    Ok thanks - I thought someone would say 'consult an SE' and we will do so, but I just wondered if it is technically possible to extend a flitch beam with a 'U' bracket or extensions and whether anyone had ever been involved in such a task? As a consumer, I always find conversations / discussions with local SE's challenging / over my head! I've not yet found one to work with who can explain things in simple terms (or maybe its just me).We've previously had an RSJ extended by welding in situ (with SE / building control involvement) so I just wondered if similar was possible with a flitch beam?

    Any thoughts on building the vertical apex post and wind braces into the stud wall, as this is my most pressing need? It seems to be such a specific query that I can't find it on any forums or loft-conversion DIY sites.

    Thanks again - much appreciated.
     
  4. stevie22

    stevie22 Screwfix Select

    In another life I was a lecturer so I always try to explain things in lay terms to my clients (and generally succeed).

    There are 2 issues:

    1. the size of the beam. Beams are designed for deflection criteria as well as strength and this is almost always the critical one. The required stiffness in the beam depends on the span multiplied by itself 4 times so a 10% increase in span requires something like a 50% increase in beam capacity.

    2. assuming it would still work the mechanics of extending. You would have to strip back the timber to extend the plate and then find a welder who is coded to do butt welds and coded to do site work and willing to stand in the middle of a potential bonfire creating sparks. Then the wood needs to match the length for the flitch to function properly. Or you come up with some kind of a bracket remembering that it will need to be rigid

    Wind braces in lofts not common so again this is something that an SE needs to look at in detail
     

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