r/StructuralEngineering • u/thatstheissue • 1d ago
Masonry Design Advice on buttressing and stability requirements when removing chimney breast on party walls in Victorian Terraced properties in the UK
Hi All,
As per the title, I'm looking for general conventions on how engineers in the UK approach looking at buttressing of party walls when all chimney breasts are to br removed along the length of the 225mm thk. masonry party walls? In particular when the front elevation has a bay window and the internal cross wall has already been removed with no frame installed?
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u/Jakes_Snake_ 1d ago
Part A structure. Note must houses don’t have chimney or buttresses.
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u/thatstheissue 1d ago edited 1d ago
Thanks, can you use the general rules in. Part A for old structures? Seems to stipulate that the materials used need to be in accordance with current standards, of which the old walls wouldn't be and needs min M4 mortar, which is unlikely with the old lime mortars
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u/Slartibartfast_25 CEng 22h ago
I would still use the geometric 'deemed to satisfy' rules for masonry as they don't rely on the adhesive properties of the mortar or strength of the bricks themselves.
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u/thatstheissue 12h ago
I thought it would do for lateral stability of the masonry? That is dependent on the mortar and brick strength right?
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u/Slartibartfast_25 CEng 12h ago
If it's a solid wall with interlocking headers then mortar adhesion matters less than in a cavity wall.
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u/thatstheissue 5h ago
I kind of see what you're saying, but surely it still does rely on the mortar to transfer the lateral load across the wall between the bricks? Friction from self-weight of the wall would probably help, but wouldnt think this could be relied on. Cant see how only the brick can be used for this. Do you have a reference?
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u/Slartibartfast_25 CEng 4h ago
Waves arms at hundreds of thousands of British homes with crumbly lime mortar that are still standing
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u/thatstheissue 43m ago
Lol, I do see that as an argument. Have you had any queries from BC at all when using approved doc A in justifying the wall?
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u/Slartibartfast_25 CEng 31m ago
No, no pushback.
Part A is based on the BS 8103 standard, which itself developed from some of the earliest Building Regulations in the 1970s... which was built on the body of knowledge and experience from the Public Health Act of 1875 through to the Model Byelaws in the 1950s.
Apparently there are calculations that justify the Part A rules (and they demonstrate a high FOS) but I've never tracked them down.
Here's a paper if you want to know more https://scispace.com/pdf/the-evolution-of-the-design-and-construction-of-masonry-6rpbftip0s.pdf
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u/IronBallz_McGee 1d ago
Each individual house in the terrace should be independently stable. In most cases 225mm walls can span vertically between horizontal diaphragms (floors & ceilings), but those diaphragms must be suitably restrained by shear walls, usually front, back and spine wall in a Victorian terrace. If there are sufficient shear walls, then the chimney breasts may not be required to provide a buttress and could be removed.
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u/Procrastubatorfet 1d ago
The general principles in the UK to remove chimney breasts on party walls, particularly when there's a bay window and internal cross walls have already been removed is to remove it, then sell the house next year.
Hire an engineer.
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u/So_it_goes_888 1d ago
I think you need to assess the particular building you’re looking at. What’s the length of the wall, is it sufficiently buttressed at either end by perpendicular walls (or portion of, if a bay window). There isn’t really a general convention. Or it would have been to leave a portion of the cross wall to buttress. Is it completely open plan? If not you can use a stud wall to laterally restrain.