Cavity lintel v RSJ query

26 Jan 2013
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United Kingdom
Hi All

We are in the process of self building a single storey extension on the rear of our property.

We are aware we need a steel ridge beam for our gable roof and have had calcs agreed by building control for this. 152x89x16 at 4.2m being deemed sufficient.
Situated approx 750mm Below each end of the RSJ are to be bifold doors. One set forming part of the extension being 2470mm wide and the other set forming part of the existing house which are 2400mm wide.
We have contacted Keystone / IG and they have specified which of their cavity lintels are suitable taking into consideration that there’s to be a ridge beam above the lintel.
They suggest a XHD90 / L5 100 extra heavy duty 2700mm lintel above the existing doors and a XHD90 / L5 100 extra heavy duty 2850mm in the extension. Both of which have a 80KN load value.
My query is about the installation of a cavity lintel above the existing doors.
I realise we can remove the appropriate number of brick courses with the assistance of acro Props and strong boys on the outer leaf to get the lintel in but how do we get the inner leaf fixed considering they are block construction? (Without causing untold disruption between our dining room ceiling and bedroom floor inside)
Additionally We believe there’s a concrete lintel on the inner course and a ‘L’ lintel on the outer course currently
Would an RSJ for the outer leaf only be a better option?
If so where can we obtain load tables to establish which size RSJ would be required?
Thanks in advance
Last edited:
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They should be able to size the beam also. Or send to Keystone lintels and they can sort for you.
I always prefer the rsj route in existing openings personally. You will be plastering this in I assume?
Do you have the point load from the ridge beam available?
Hi Siwriderby
I’ve sent a query to Keystone re a lintel, but agree with you that RSJ would be a preferred option, especially as u say it will be plastered in.

Design loads for the ridge beam 4.86kN/m (does that sound right)

I have asked the calcs guy but he’s not replied unfortunately.

Thanks Lisa

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