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We would like to remove a window and open the aperture to the maximum to fit bi-folds. how do we work out how wide is structurally safe and what type/length lintel to use?
Existing window 188cms wide, set in existing wall 346cms wide, single storey, flat roof projecting 122cms from main house structure.
6 Answers from MyBuilder Extension Builders
Croydon • Member since 5 Jul 2011 • 345 jobs, 99% positive feedback
u need structrial calculations done by serveyor we have 1 if u need thank u
Answered 6th Aug 2011
Good afternoon to carry out this work you will need to apply for building regs first. Lintels typically span 150mm longer each side than the original size of the opening. So you will need a new lintel if the bi fold is bigger than the width of the window. The lintel depends on the build of the house eg. cavity wall, nine inch solid etc.
Hope this helps
Answered 6th Aug 2011
Wellingborough • Member since 25 Feb 2009 • 37 jobs, 100% positive feedback
My advice is play it safe and seek advice from a structural engineer and also speak to local building control about building regs.
Answered 7th Aug 2011
Answered 11th Aug 2011
years ago builders used rule of thumb, but nowadays the correct way is to use the services of a structural engineer.
The width of the opening would be governed by the minimum lengths of brickwork left standing, or if an opening larger is required then alternative support would normally be required to strenghthen the walls, usually by thicker piers or extra structural or steel columns, (this presumes standard construction).
Secondly the span and loading from the roof above needs to be accounted for, and also any loading from the door system if it is hung from the beam above, this would dictate the type and strength of lintel or beam needed. (standard steel lintels come in many differing types & loading capabilities)
This work would need to comply with building regulations, the structural engineer would ensure this, and the builder would have the correct information.
Steve Nicholls BSc(Hons)Residential Development
Answered 28th Aug 2011
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