Removing cement mortar.

[aobr31569]

I've had a few issues with damp on a wall in the kitchen. Its had two injected damp courses at some point in its life, as it has holes in both bricks, and mortar, both inside and out. Its pointed with cement mortar, and the ground level outside is level with the original DPC.

I'm removing the mortar to repoint with lime, but removing the old mortar is damaging the bricks. No matter what i try, hand chisel, Armeg SDS mortar rake, grinder, causes some of the brick to come off. There is quite a lot of spalling lower down, which I guess will fail when the old cement comes out.

Is there anyway to remove the mortar and not cause any additional damage to the bricks, or is it just a fact that I have to try and deal with?

House was build in 1905.

 

[Feltwell]

What disc / fitting have you got in the grinder, and what size grinder is it?

Used very VERY carefully, I've found a 4 1/2" angle grinder with a diamond disc is the best to cut enough out whilst avoiding damage to the brick face. Messy, noisy, horrible job though!

 

[GRADE_II_MONEYPIT]

How deep is the cement mortar? Is it really hard? Perhaps you can turn the damaged bricks?

Post a few photos if you get chance.

It is likely most of the damage has been done to the soft bricks with cement mortar in place.

However, the use of power tools was expressly forbidden during removal of cement mortar by my lical CO and in the hands of anyone other than the highly skilled more damage can be done by a grinder than any cement.

 

[plasticpigeon]

I also have found that using a diamond disk in a 4.5" angle grinder to cut a deep groove down the middle of the mortar joint and then chipping the cement out either side gingerly with a hammer and chisel does the least damage. The groove allows the hard cement to be chipped away from the brick and into the grove. I have tried chipping out with a hammer and chisel without making the groove first and always end up chipping the edges of the brick. If the cement is really deep this might make this process more difficult, but I imagine lime pointing will still be kinder to the bricks even with cement behind.

 

[Penners]

I also have found that using a diamond disk in a 4.5" angle grinder to cut a deep groove down the middle of the mortar joint and then chipping the cement out either side gingerly with a hammer and chisel does the least damage. The groove allows the hard cement to be chipped away from the brick and into the grove.

I agree that this is probably the most promising technique. As PP suggests, make your groove quite deep, then work with a bolster from each side of the mortar line, collapsing the mortar inwards into the groove.

But the chances of causing zero damage are, I'm afraid, pretty remote.

 

[aobr31569]

I've been using a 115mm angle grinder/disk. The disk is one designed for mortar removal, 6mm thick I think. Maybe thats the issue and I need a thinner one, but even when the mortar breaks out before the cut, it pulls bits of brick with it.

Mortar is probably 10mm deep average.

 

[DJH]

There's a common misconception that cement render is the only cause of the face of bricks spalling. This is not entirely true... cement render was used years ago to actually cover over cheap under fired and substandard bricks which were used for a variety of reasons mostly economic but also availability, colour match, not caring and also because they would be hidden under the render so it didn't matter.

Doug