Knocking out bricks in chimney stack to clear internal block

[davidbeaven]

Had the chimney swept but the sweep couldn't get past the second bend. Looking down from top he could see some mortar stopping his rod. He suggested I could go in from side of chimney, remove the blockage, rebrick and reseal with fire clay
It is a 2 and a half brick wide square double brick thickness chimney. I have started to remove one half brick in the middle above the bend (i.e. about 10ft below top of stack).
Any ideas on how many bricks it is safe to remove from outer skin and from the inner skin, and if so in any particular pattern?
Thanks
David

 

[Aqua]

I had a similar problem,

First if you can see overhanging mortar looking down the chimney, can you not use a metal rod or similar to knock the mortar off therefore clearing the blockage.

If this is no good you may want to install a metal box in the loft to allow the top part of the chimney to be swept from there, this is what i had to do.

My chimney is single brick and i took out as much as required to fit the box and then remade around the box, there was no problem with other bricks moving etc.

As yours is double brick you would need to take care not to allow bricks to fall down the chimney and if you fit a box it must go through both sections of brick work.

You will need more bricks removing from the loft side to allow you to work on the inner bricks, if you are worried about taking out quite a few bricks, prop the bricks above with wood etc while you carry out the work.

If you don't fancy the job ask your sweep to do it or a builder, it should only take 2-4 hours max.

 

[snozzer]

Think of a triangle when removing the bricks. In practice by removing a triangle of bricks you create the same effect as an arch. So to get a reasonable opening try removing 3 bricks on the 1st course, 2 on the 2nd and 1 on the 3rd, so the opening is a nice neat triangle, then the forces above are distributed around the opening. I have opened up very big spaces like that. On one job in a cellar I removed 20 bricks wide at the base and the BCO was absolutely fine with it (No serious load issues above).