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Holes are made in brickwork walls for all kinds of reasons including gas flues, to route cabling and to fit windows. At some point that hole gets large enough that a lintel is required to support the brickwork above.

My questions are:

  1. My theory is that the height of the hole is not relevant as to whether additional support is required. The only important factor is the width of the hole. Is this correct?
  2. Is a circular or rectangular hole preferred?
  3. Does the type of construction i.e. cavity wall, double leaf solid wall, single leaf wall make a significant difference?
  4. What is the maximum width of the hole before additional support is required?
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  • $\begingroup$ Check out corbelling. $\endgroup$ – Solar Mike Sep 22 '20 at 9:34
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Direct answer to your questions:

  1. Yes, the opening depth is immaterial in support requirement determination.

  2. Round opening is less likely to require support, due to arch action.

  3. Wall type is critical when the brick layout pattern affects the available bond between bricks over the opening.

  4. If depth of the wall above the opening permits arch action to occur, the bricks below the arch action zone will fall if the bond is insufficient to hold the weight of the bricks

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In case nobody else answers I have found this in UK Building Regs A - Structure.

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Limiting penetrations without additional structural support to 0.1 m2 at 2 m centres seems like a reasonable enough rule of thumb.

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  • $\begingroup$ Your "rule of thumb" is not "reasonable" since it ignores the content of the referenced Building Regulations, in particular for doors and windows. Installing lintels over every door and window is completely unnecessary. $\endgroup$ – alephzero Sep 22 '20 at 15:51
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As general, design of lintel is much similar to designing a simply supported beam, depending on the architectural purposes, you can easily get the loading and do the design without involving complex analysis.

  1. The height of the opening (hole) is irrelevant to the design on lintel, however, greater height of the opening would also directly indicates that the stiffness of the wall is reduced and may required stiffeners to strengthen the wall at its week axis.

  2. For construction wise, rectangular opening is easier to construct. Circular hole would sometimes requires hacking and cutting of brickwork, and its best to avoid such activities.

  3. Yes, totally, double leaf solid wall would logically be the heaviest amongst, unless the cavity wall is filled with other construction material based on its usage. In short, the thickness of the wall would affect the dead load onto the lintel, which indicates that greater size of lintel would be required.

  4. You may refer to masonry design requirement, however the country I worked in does not even bother about it. Up to my knowledge, workmanship plays an important role in masonry. Besides, material wise, the strength of bricks is required to do load test frequently to ensure that it is up to allowable strength. However, when required, pipe sleeve installed in brick wall can serve the purpose too.

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