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Frost damage to brickwork and mortar

Discussion in 'Building' started by james_bristol, 14 Mar 2011.

  1. james_bristol

    james_bristol

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    2 years ago I built some raised brick flower beds in my garden and all seemed well but the last two winters seem to have taken their toll on both the bricks and my amateur bricklaying.

    Many of the top bricks have lost the top couple mm and several are very loose as the mortar seems to have blown out. I guess this is due to frost damage but what I would really like advice on is how to avoid it when I sort it out this year.

    The "walls" are single skin and 6 bricks tall at the highest point, 2 bricks at the lowest (sloping garden). I used LBC Heathers as they were the closest match to the existing house and outbuilding bricks.

    Any advice will be greatly appreciated.

    Many thanks
     
  2. ^woody^

    ^woody^

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    London bricks are the worst possible choice for garden walls and exposed brickwork - they are bad enough on house walls

    You need to sort out some decent bricks - look for ones with a "FL" rating which indicates frost resistant

    Also consider using a solid engineering brick (and tile crease) or proper coping stone on the top. An overhang protects the wall below

    And mortar should be no less than 4:1 and make sure the joints are properly compacted and smoothed with the trowel or jointer to give them the weathering protection they need

    IIRC, Hanson do some bricks similar to London heathers
     
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  3. james_bristol

    james_bristol

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    Thanks for the info. Looks like I will have to decide whether to replace the top level of bricks with something similar but more suitable or cap the existing bricks and hope for the best.

    Just to clarify: when you say no less than 4:1 do you mean don't have any less cement (therefore 3:1, 2:1 is ok) or do you mean no less sand (therefore 5:1 is ok). Sorry if it is obvious but I am not sure which of the two parts is causing the vulnerability to the frost.
     
  4. ^woody^

    ^woody^

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    No less = no weaker = no greater sand to cement ratio. So 3:1 is OK but 5:1 not OK

    Don't go any stronger than a 3:1, as this will then be too strong and liable to crack
     
  5. DIYnot Local

    DIYnot Local

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