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Patio awning - load on wall

Discussion in 'Building' started by blup, 9 May 2018.

  1. blup

    blup

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    I am planning to install a patio awning 5.5 metres in width by 3 metres depth, above double patio doors. Above them is a bedroom window. There are 19 courses of brick between the top of the doors and the underside of the window above. On one side the edge of the awning will be approximately 1 metre from the edge of the wall.

    The wall is a double skin of brick and block with insulation, so the awning brackets will be drilled - with resin based anchor bolts - through the outer (brick) skin only.

    Is it likely that the wall can take the load of the awning given the information above?

    Any comments/observations much appreciated.

    Cheers,

    Blup
     
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  3. bernardgreen

    bernardgreen

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    More information needed. Type of awning and condition of brickwork and mortar in the wall.

    The weight of the awning creates vertical and horizontal forces on the wall.

    The wall will take the vertical forces as they just press the bricks down, unlikely the bricks will crumble.

    The horizontal forces from a heavy awning may exceed the strength of the wall.

    The top awning shown in the image exerts less horizontal forces on the wall for the same over all weight of awning.


    [​IMG]

    Also consider the effect of wind blowing onto the slope of the awning. That can add significant extra "weight" to the awning.
     

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  4. tony1851

    tony1851

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    At least some of the fixing bolts will be in tension. You will be hard-pressed to find 'pull-out' values for bolts fixed into brickwork; completely unknown quantity.
     
  5. blup

    blup

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    Thanks BG.

    Your point about the different forces exerted with different awning angles is noted.

    The brickwork and mortar are in good condition (a 12 year old extension), the bricks have three vertical holes instead of a traditional frog, but I believe resin fixed bolts - properly installed - should suffice.

    Would the weight of 19 courses of bricks above the awning fixing points be sufficient - all other things being equal - to counteract the force from an open awning of the dimensions I have described?
     
  6. tony1851

    tony1851

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    If you are bolting brackets to the wall, it's not just a case of 'will the weight of bricks be sufficient'.
    The bolts will be subject to both shear (downward force) and tension (outward pull).

    Look at BGs drawing; the top horizontal arrows show the outward pull on the bolts. You could have 1 million tons of brickwork above, but
    that would not mean that the bolts would not pull out.

    As masonry varies very widely in strength, and as you can never be certain how much resin is actually holding the bolts, and as you cannot guarantee there are no internal cracks in the bricks, there is no accurate way of knowing whether they will resist any defined force. The fact that the bricks are perforated does not help. This is why manufacturers will never quote figures for maximum pull-out force for their products.
    All you can do is put in as many fixings as you can, even if it looks like overkill.
     
  7. blup

    blup

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    Thanks.

    It is difficult to see how any awning could be safely fitted to external wall of a house given the uncertainties you refer to, unless a structural engineer's report was prepared, which could cost more than the awning, certainly the cheaper ones.

    I mentioned the 19 courses because advice elsewhere on this forum has indicated there would be considerable risk installing an awning on the wall of, say, a flat roofed single storey building, where the fixing brackets were only several brick courses below roof line. It seemed to me that that wouldn't apply if there was substantial brickwork above, but I wanted to check.

    I am prepared to "risk" the fixings pulling out, but less happy that the brickwork might fail in some (possibly catastrophic) way.

    Has anybody else fitted an awning into "modern" brickwork, and what were your experiences?

    Cheers,

    Blup
     
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  9. garyo

    garyo

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    Does the manufacturer recommend a fixing type and size? The concept makes me nervous with the snow we've been getting in this country over the last few years.
     
  10. Ian H

    Ian H

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    Could you put legs onto the opposite side?
     
  11. blup consider purchasing an awning and installation service at the same time,seems you dont care much about 'risk'.
     
  12. blup

    blup

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    Thank you all for the various suggestions, I care about the risk as I identified it.

    If I asked a builder to install, I suspect he would carry out the job, but at my risk.

    Similarly, if the supplier installed, I would be asked to sign a disclaimer to the effect the wall was structurally sound, and all was done at my risk - in the same way the small print in double glazing installation contracts excludes such liability.

    So maybe back to square one............
     
  13. blup

    blup

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    I have done some further research after contacting an awning company who say various brackets can be specified for single storey buildings, or where large awnings require further fixing points in the wall.

    They use spreader plates, and various shaped brackets to deal with gutters, downpipes and other obstructions as per the following photos. In extreme cases "goal post" brackets will be specified.

    It's usual for the supplier to send a surveyor to identify what additional brackets may be required to deal with sheer forces and pull out forces of the retractable awnings where the existing substrate isn't adequate:

    [​IMG]

    [​IMG]

    [​IMG]
    [​IMG]
    [​IMG]
     
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  14. DIYnot Local

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