Repointing old bricks, not sure what mortar to use and how deep.

28 Jul 2015
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United Kingdom
I've got to some brickwork repairs to an outbuilding, it's quite old around 120 years+

The pointing is on the inside, as it's pebble-dashed, some of the current mortar I've scrapped back 25mm from the brick face.

The bricks are the old slim type hand-made jobs. The mortar looks to be lime based (guessing) with some sharp sand in there.

There are also few bricks to chop out here and there (water damage from crappy roof) and I'd like to make the job as strong a possible... so do I use normal sand/cement mortar, or should I use something else with lime?

Are lime mortars strong enough when compared to modern sand cement?

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25mm deep is enough.

If the existing is lime, then you really should use lime mortar for repairs. Hydraulic lime and not the typical and more common hydrated lime in the merchants.

But as it's internal and limited, then you could use a weak 6:1 sand:cement mix instead.

The idea of making it "as strong as possible" is wrong, as all that will do is crack as the rest of the wall moves differently, and actually serves no purpose for isolated repairs.
Thanks for the reply, I wasn't expecting such a weak mix.

Sorry to ask another question, upon inspection I need to replace a length of wall plate due to water damage/rot.
Would this 'lean mix' be suitable for this too?

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Yes it will be OK. The thing to rember is to iron the face of the joints well, and this makes it more wear resistant, which in turn protects the rest of the mortar behind.

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