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Thursday, 13 October 2011

Gallows brackets-How to install them

Gallows brackets are metal supports, triangular in shape used in combination with a pre stressed concrete lintel to support the chimney stack in the loft when a chimney breast has been removed on the floor(s) below.Different councils have slightly different requirements when it comes to the installation of Gallows brackets and while one will insist on 3 gallows brackets to support the brickwork above another will require just 2. The strength of the gallows brackets will also need to comply with council specifications which means the flanges will have to be 3 inches wide and not 2 inches as was the case in the old days. Because the chimney flues are bonded into the main party wall there is no need to be too concerned that the whole stack will come tumbling down and I have seen cases where the only thing supporting the stack in the loft was the grace of God.
Before embarking on a project like removing a chimney stack always notify the council and be safe rather than sorry as they will advise the best way forward and there will be no worrying when it comes to selling the house as everything will have been carried out in accordance with building regulations. Remember also that if you share a party wall with your neighbour you may need a Party Wall Agreement.
The process of installing the gallows brackets is pretty straight forward and can easily be carried out in a day but great care has to be taken to ensure you do not fall down through the ceiling as this can ruin your whole day.

You will need
1. 3 gallows brackets
2. 1pre-stressed concrete lintel 9inches wide (2 lintels 4 inches wide are easier to carry) or metal plate
3. 6 rawlbolts to bolt the brackets to the wall
4. 1 drill with a 16mm drill bit
5. Sharp sand and cement mix to use as drypack between the top of the lintel and the underside of the brickwork

Sequence of operations installing the Gallows Brackets
1.Drill 6 holes (two per bracket) where the Gallows brackets are to go i.e one bracket must go on either side of the stack and one in the middle.

2. Offer the gallows brackets to the wall and put the rawlbolts through securing them tightly with a spanner.


3. Span the lintel across the gallows brackets

4. Mix up 2:1 sharp sand and cement mix better known as drypack (damp not wet) and insert it between the lintel and the upper brickwork forming a very strong bond.


This is not a very difficult job to do, but given the dusty conditions and absence of good ventilation in your average loft, it does warrant the use of a good quality dust mask.( and at least six pints of a good quality lager to ensure no possibility of a dreaded sore throat. This is entirely optional... but highly recommended :)


12 comments:

  1. I just used your advice to install a lintel under my chimney stack - very useful, many thanks!

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  2. What holds the top part of the chimney up whilst you've removed the bottom half prior to fitting the gallows ??

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    1. Because of the way the bricks are bonded into the party wall there is no need to support the upper stack for the short period of time that it takes to put in the gallows brackets.Remember that there are a lot of chimney stacks in London that have been unsupported for years.This is not recommended and will deter prospective buyers when it comes to selling the house

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  3. Nice post About How to install them brackets Rawl bolts

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  4. Excellent thanks.
    I myself drank the six pints first and fell through the ceiling.....didn't feel a thing !! ;)

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  5. I'm looking at doing this but like another person posted in a little concerned about supporting the chimney prior to putting the brackets & lintel in, don't I need to make some sort of A frame (my chimney is like a wishbone in the attick but the side I want to take out is straight) rather than both being curved! Any help much appreciated, also best place to buy the brackets and sizes needed

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  6. what is the size (dia or length) of rawbolt for gallow bracket use

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  7. What is the space required between the metal lintel and underside of stack to fill with cement/sand mix? Would it not be better bolting the brackets with lintel directly under the row of chimney breast bricks, so not risking the cement/sand mix crumbling over time.

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  8. I am looking into this for my own house and I can answer the previous person's question. Apparently the sand/cement mix is important and it ensures there is no gap. This is better and safer than trying to ensure that your bricks are totally level, which would be really difficult to achieve. I hope this helps.

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  9. I am about to fit the 3rd gallow bracket, first two really strong An secure, what I’ve noticed is that brickwork in centre is a list shallower about 4inchs can I proceed with this making my bolts shorter, first two where 7inchs into the wall....

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  10. my chimney has been terminated within my loft. Not sure how it is being supported as I haven't lifted the floor boards within the loft yet. Either way, I am planning to install gallows brackets to support the chimney. I am having a wood burning stove installed on the ground floor. My builder is building a fake chimney breast within the lounge and a twin flue (boxed) rising to chimney stack within the loft. My question is, if I install the brackets, would it be best to support the stack with a steel beam as apposed to concrete lintel so that the flue can connect into the chimney within the loft space? thanks in advance.

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