Re-pointing using lime mortar - remove cement mortar first?

[Superhans]

Hello,
I am in the final stages of buying an Edwardian end-terrace property and this website has been an excellent resource to help me understand the original features and building technique so, thank you!

The property is in need of attention in all aspects, but foremost it needs re-pointing. From reading articles on this website and others, I gather that lime mortar is recommended to act as a sacrificial, breathable layer between the bricks (in this case, Accrington bricks). I think it's quite likely the property has been re-pointed with cement based mortar in different places at different times, which worries me because I've read that cement based mortars can cause damp problems in these types of properties due to acting as a water repellent barrier and increasing the rate of freeze-thaw degradation in the bricks.

So, should I be considering removing all traces of cement based mortar before re-pointing using lime?

 

[King of the Monkeys]

You need to remove the vast majority of cement ...ie. leaving less than 1/1000 th , it needs to be removed and replaced with a lime mortar. What ever material is in the joints it needs to be removed if re-pointing to ensure sufficient key to the substrate.

 

[plasticpigeon]

I'm convinced that cement pointing, if hard can cause the face of the bricks to spall, as any water between mortar and brick that freezes will damage brick not mortar. Not so sure about causing damp, but it won't help evaporation. If hard, the cement will need to be taken out by grinding a channel down the middle of the joint with a thin diamond blade, and then chip the rest away into the channel to minimise damage to the brick edges or arris. if you try and take the pointing out in one go it will probably damage the bricks. Accrington brick is very hard and strong though. It's world famous isn't it? So maybe less troublesome than in other period buildings. Alsdo was lime mortar the original mortar used??

 

[Roger H]

Hi Superhans.

Removing cement pointing can be tricky and potentially cause damage. Is the pointing literally falling out, or are the bricks spalling because of the pointing, or is there damp already inside with cement as the likely culprit? As ever, some pics would help.

 

[formerly known as]

My advice would be to take a sample of the ORIGINAL pointing mortar and get it analysed. Also inspect to see if the pointing mortar is different to the bedding mortar - they can differ. A building of this age might well have a compo mortar.

 

[Superhans]

Thank you for the replies. I will drive past the house on Saturday and get some more pictures. I've got one picture of what looks to be re-pointing using typical cement mortar here (besides the other problems in that picture :shock:
http://i.imgur.com/hNdPATO.jpg

There are examples where the existing mortar has fallen out or recessed, leaving a thin 'shelf'. I gather this is bad. There are also occasional bricks showing signs of spalling at the edges or (rarely) across the entire face.

I would certainly be removing the cement mortar if it's already degraded. But is it worth removing the cement mortar pointing if it's in good condition? An added complication is that the joints between bricks are quite narrow, making it more difficult to remove without causing brick damage.

At the risk of derailing the thread, I've just looked on street view and noticed what look like holes drilled into the bricks:
http://i.imgur.com/pSnO1bM.jpg
(sorry for low quality image, as I said I'll get some better ones this weekend).

What could these be? I hope it isn't chemical damp proofing..?

 

[plasticpigeon]

My 2 pence worth is that that is lovely brickwork, the thin joints are very attractive. I only have brickwork like that on the front of my house. Anyone that has touched it in the past has damaged it. It is hard to rake out hard pointing without damaging bricks with such thin joints, so I would leave anything that is solid, and just repair areas where it has fallen out. Try and use hand tools if possible.

 

[Superhans]

My 2 pence worth is that that is lovely brickwork, the thin joints are very attractive. I only have brickwork like that on the front of my house. Anyone that has touched it in the past has damaged it. It is hard to rake out hard pointing without damaging bricks with such thin joints, so I would leave anything that is solid, and just repair areas where it has fallen out. Try and use hand tools if possible.

I think you may be right. I'll get the opinion of a restoration specialist as I need their advice on removing some external paint. For some reason the front of the house is painted red up to the first floor.. God knows why :? It seems to have been fashionable as almost all the houses have the same rusty red colour.

 

[TheRoost]

Your gable end appears to have a case of chicken pox! If the red marks on the bricks aren't just some defect in the google image, I would definitely have a closer look at them yourself, and/or ask your surveyors opinion. The gable is built in stretcher bond, so guessing the house has cavity walls? it would be silly to drill into bricks all the way up a wall to inject chemicals, but I wouldn't put anything past them. Could it be replacement cavity wall ties, because the joints were too narrow to drill into?

It is very nice brickwork. The front of my place is built from a hard iron-rich Accrington type brick, has smallish joints and was repointed 15-20 years ago in cement, it looks messy but it doesn't seem to of done any harm yet (I plan to remove it all one day..one day!)

The first picture looks more like tool damage than spalling to me, as if someone has tried to remove pointing(or tried to remove a brick) near that vent and caused damage.

 

[malcolm]

The cement pointing looks like a poor job. Normally when the original pointing has recessed a little someone comes along and splashes cement around in an untidy manner without bothering to do any raking out. The cement might only be a couple of millimetres thick and should pop itself out on the first decent frost if the wall is damp.

It is a time consuming job to remove cement mortar then rake out, and the bricks are likely to suffer some damage where the cement has stuck to the edges. I would consider leaving it for now and let nature remove the cement for you over time. That's the approach I'm taking with my cement pointed wall (together with occasionally picking the cement out with my finger nails when I'm passing) - the wall was pointed badly maybe 20 years ago so most of the cement is nicely loose and falling out by itself.

 

[Zebra]

If it is a cavity wall, aren't those holes likely to be injected cavity wall insulation?

 

[stuart45]

The pattern of holes suggests wall tie replacement. Usually every 6 courses and 4th brick along, staggered. Normally through the brick rather than the joints.