Removing cement from brickwork

[Timw]

I have an early 1800's house that was built with bricks and lime mortar. Unfortunately the previous owner did some impromptu patches of repointing with cement. Much of the cement is smeared over the brickwork as well as in the joints.

I have read that it is very difficult to remove cement from brickwork, but does anyone have any tips?

Tim

 

[Penners]

In my inexpert experience, it's down to luck. Sometimes the cement will stick like wotsit to a blanket, while other examples come off pretty cleanly.

It may be a question of how well (or otherwise) the cement rendering was put on in the first place, plus the variations in key that different types of brick offer.

I think the only thing you can do is have a go at a small test area with a hammer and bolster. Try to ensure that your hammering is carried out at a very oblique angle to the wall face, to reduce the risk of disturbing the bricks.

Other, more qualified people, may add expert views.

 

[Lime]

As Penners says removing cement off bricks can vary even from one brick to another in the same wall.
If there is not much cement on the bricks except for smearing then a proprietary acid cement remover will take it off.
However do not expect the job to be done quickly.
I recently removed old cement off some of my house bricks (the remains of a cemented path long removed) and had to use an angle grinder with a wire brush to encourage it to come off.
However do not use such an abrasive unless the bricks are very hard otherwise the brick face will come off too.

 

[NT]

Having tried hammer & cold chisel, angle grinder and SDS, here's what I found.


SDS is fast but easy to do damage. Avoid.


Hammer & chisel is the middle option performance wise, and the slowest of all.


Angle grinder is the gentlest IF used very very gently to cut a slot along the centre of the pointing. By very gently, just ignore the noise and imagine its a delicate artist's tool, apply almost no pressure.

By cutting the cement into 2 by slotting it, this allows the remains to move in directions that avoid damage, whereas the cement coming out whole is more likely to damage. Also the vibration often causes even hard cement to simply drop off.

The downside with angle grinders is the temptation to push it. Do so and you'll do damage rapidly. So I'd use an angle grinder, but wouldnt want others to do so if they were on piece rate.


NT

 

[Gervase]

If you are going to use an angle grinder - and they need huge care if you're not to injure yourself or the wall - don't use a masonry disc, as that doesn't give either the depth or the control.
Invest in a mortar rake, but go for one that is considerably narrower than your pointing. The diamond rakes are also extremely useful if you ever need to remove a brick.

 

[Gervase]

...and for the mortar buttering, a semi-flex sanding disc on an angle grinder - again used with great care - can be useful, but not if you have very soft brick.

 

[Penners]

Gervase - please can you explain the problems associated with grinding the face off a brick (other than aesthetic)? Is a brick not homogenous right through?

 

[Lime]

Gervase - please can you explain the problems associated with grinding the face off a brick (other than aesthetic)? Is a brick not homogenous right through?

Bricks are like a plum pudding cooked in linen.
They are all the same stuff except the outside is smooth and flat whereas the inside is often crumbly.

God that's made me hungry!

 

[Penners]

Bricks are like a plum pudding cooked in linen.
They are all the same stuff except the outside is smooth and flat whereas the inside is often crumbly.

God that's made me hungry!

Thanks, Lime. At last you've explained to me why bricks get "buttered"!

 

[Gervase]

Bricks are like a plum pudding cooked in linen.
They are all the same stuff except the outside is smooth and flat whereas the inside is often crumbly.

Very similar, in fact, to my beloved's gingerbread. If you'd ever tasted it, you'd realise why houses can actually be made of gingerbread!

 

[Penners]

Very similar, in fact, to my beloved's gingerbread. If you'd ever tasted it, you'd realise why houses can actually be made of gingerbread!

Is that really a wise comment, 24 hrs before the busiest cooking day of the year? :shock:

 

[Gervase]

No problem really, as I do 90 per cent of the cooking in our household, leaving herself to deal with cakes and chutneys (plus the fact that she just raises her eyebrows and mutters darkly about 'honestly, bloody lime bores...' when she sees me tapping away here)

 

[Penners]

I do 90 per cent of the cooking in our household

Well, you can be sure that there's a certain wife, not a million miles from where I'm sitting, who won't be reading that post, if I have anything to do with it.

 

[NT]

If you are going to use an angle grinder - and they need huge care if you're not to injure yourself or the wall - don't use a masonry disc, as that doesn't give either the depth or the control.

Why do you say that? I didnt find any problems with a diamond disc.


NT

 

[Gervase]

I have to confess that I've only tired using a disc on one job. That was with a 4.5 inch disc and, when doing the verticals, I found I was able to go a only very small way into the mortar at the tops and bottoms of each brick, and so resorted to a plugging chisel to do the job neatly.
Then I bought a couple of raking bits and found them much easier and more controllable - with the added advantage that you can regulate the depth of cut very precisely if you want to remove entire bricks.
That said, most of the time I use a plugging chisel and a home-made bick because I'm working on stone rather than brick - and on old brick I prefer to use a combination of drill and chisel - because if the grinder suddenly hits a patch of soft mortar after ploughing through cementitious stuff it's all too easy to skid into the arris of a brick.
I wish I had the control and confidence to use a grinder all the time, but I fear it's not for me.

 

[NT]

I have to confess that I've only tired using a disc on one job. That was with a 4.5 inch disc and, when doing the verticals, I found I was able to go a only very small way into the mortar at the tops and bottoms of each brick,

Yes. Thats good enough for removing cement pointing as the vertical cut makes it almost entirely cut through at top & bottom of the brick, and the horizontal cuts that follow above & below do the rest.

Small remaining cement bridges break easily too.

It would be a different matter for bricks laid in cement mortar full depth, but with lime mortar the cement pointing is left with nothing to cling to and so weak it mostly comes away with a bare finger, IME anyway.

Then I bought a couple of raking bits and found them much easier and more controllable - with the added advantage that you can regulate the depth of cut very precisely if you want to remove entire bricks.
That said, most of the time I use a plugging chisel and a home-made bick because I'm working on stone rather than brick

Are you thinking of brickwork laid in lime or cement? Where I needed to dig deep on lime a screwdriver had it out almost as quick as a power tool. Cement is another story though.

- and on old brick I prefer to use a combination of drill and chisel - because if the grinder suddenly hits a patch of soft mortar after ploughing through cementitious stuff it's all too easy to skid into the arris of a brick.
I wish I had the control and confidence to use a grinder all the time, but I fear it's not for me.

I think that comes down to technique. Last wall I did the mortar was a hotchpotch of hard cement, soft cement, lime, earth and nothing, and it went fine. One has to control position as much as pressure. I think its one of those tools that can go very wrong, depending on how its used, but I found it the best of all the options I tried.


NT

 

[Timw]

Thanks for all your contributions.

One question regarding raking bits for angle grinders; I see that you can buy some kind of guide gadget for these bits. Has anyone ever used one? Does it simply regulate the depth of cut, or does it enable you to maintain a straight cutting line along the joint too?

 

[Lime]

I have used a small angle grinder with a diamond disk several times to remove cement from walls.
It is important to have a good well balanced grinder as some are more noisy and difficult to use than others.
The ones I prefer have a hood that is altered by a sprung clip rather than a screw or bolt as this allows for easy, quick altering of angle and cut.
It sometimes helps if the wall is wet too.

I treat each brick separately rather than attempt to do the whole wall at once. That way the job does not appear too overwhelming and results in a better job with a good appearance.
With care and suitable protection for face, eyes (ears) and hands it is possible to be like a sculptor revealing the hidden brick from out of it's coat of cement.

I would not used a guide.
The bricks are never in perfect straight lines, level or exactly the same so a straight line stands out like a sore thumb on such a wall.
Depth of cut is controlled by positioning the fingers on the wall while holding the angle grinder to give control and support rather like a sign writer leans on the work they are painting.

There is no substitute for skill.

 

[Gervase]

Agreed - the guides don't really help; freehand is best, but do it a bit at a time as your wrist will ache like beggary!

 

[Anonymous]

Timw,

I've not had to remove cement from brickwork yet, but I can certainly recommend using a selection of chisels and a brickie's hammer to clean the cement off the brick faces. I found whilst removing cement from stone, that the best chisels for doing so with minimal marking to the face are fairly fine ones (10-25mm tip), but as others pointed out, it depends on your situation.

It really depends on how large your wall is and how much time you have... a neat job CAN be done using the hammer and chisel method to remove the pointing itself. I wouldn't recommend using a plugging chisel in brickwork because I think the cement will cause the face of the stone to break off.

Hope it goes well anyway!

Peter