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Cavity Tied Into Solid Wall?

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#1 Mike1784


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Posted 05 June 2015 - 08:51 AM


I'm currently looking into extending our flat to include a glazed side rear extension with inclined roof and bi-fold doors in which to put a galley kitchen. The property is a 1930s end terrace which I'm fairly sure has solid wall construction based on the brick pattern and wall thickness.

I'm currently getting an SAP assessment on the advice of BC to ensure the design meets Part L of the building regs but I suspect in order to meeting the thermal efficiency requirements I presume the extension wall will need to be a cavity wall?

If this is the case is it acceptable to tie in a cavity wall into the existing solid brick wall building and if so are there any special considerations which need to be taken? I'm reluctant to consider a solid brick wall extension as we are keen on having exposed brickwork internally as part of the design and I fear this would fall well below part L of the BC requirements. We also would probably not get planning permission to clad the externall wall to increase the insulation.

Any help would be great


#2 tony51


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Posted 05 June 2015 - 10:10 AM

If only to keep out a potential damp-penetration problem, you would want a cavity wall.

There is no issue joining a cavity wall to a solid wall - the builder will cut a slot and insert a vertical dpc.

If the extension is to be highly-glazed, you can compensate by putting additional insulation elsewhere, eg in the loft.

#3 tonyshouse


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Posted 05 June 2015 - 11:56 AM

Use wall starters to allow for differential movement and I always avoid but joints as internal corners are essays to sort out cracks in,

#4 brickie


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Posted 05 June 2015 - 12:12 PM

View Posttony51, on 05 June 2015 - 10:10 AM, said:

There is no issue joining a cavity wall to a solid wall - the builder will cut a slot and insert a vertical dpc.http://www.maannews.com/Content.aspx?id=673479
Have to disagree there-unless the vertical dpc carries right through the wall (I.e. Into the room) it's not serving much purpose IMO,given that the original house is solid walled construction.

Edited by brickie, 05 June 2015 - 12:13 PM.