repointing a 1930 external solid brick wall

[mauro76]

Hi,

I recently bought an house, built around 1930.
The internal wall of the bedroom showed some humidity patches, and looking at the outside wall, exposed brick wall, I can see it needs some repointing.
Someone recently has made some minor patching in a couple of places using portland cement, and I think that was a bad idea as the wall is likely to be made with lime mortar.

I think I have two options:

a. rake the loose mortar, and repoint where it's missing. I would dig about 1/2 inch for the mortar to bind

b. do the complete job, removing all the mortar and repointing everything

Obviously b. would be ideal, but I fear to not have enough time to complete the job before starts raining again. With a. my concern instead it to not be able to match the colour.

Either way, what would be the right mortar? I'm attaching a photo of it, showing in the middle the "internal" mortar and then the "external" one, which seem to have a different consistency. I thought someone has re-pointed quite recently, but given other houses on the road have identical materials, I'm thinking if the builders originally used a different mortar when pointing?

I have been suggested to use an NHL 3.5 mortar, would that be OK?
Hardest part would be to match the color.

Thanks anyone for reading!

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• mauro76
• 1 Sep 2013
• 1

 

[catlad]

Solid brick 1930 are you sure ?

 

[mauro76]

Thanks catlad.
See below wall pattern. I'm pretty sure it's solid bricks also because I was told by a company that I couldn't have cavity insulation done as my wall is made of solid brick.
I'm not really sure about the construction time thought. Between the house documents there are only mentions to assumed construction date, not a definitive construction date. I guess the original documents have been lost between house owners. What time do you think it was built? It's also suspended floor if it helps.

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• mauro76
• 1 Sep 2013
• 1

 

[catlad]

Yes it looks like solid wall to me and they are generally very cold, there are a lot of houses now being insulated and cladded/rendered, that would eliminate the need for pointing.

 

[tony1851]

As per catlad, solid walls not particularly common by the 1930s, though there are some.
That brickwork pattern is Flemish bond, with alternate stretchers and headers. On the face of it, it looks solid, but some builders used half- bricks to make up the pattern and give it the appearance of a solid wall, while actually building it as a cavity wall.
The only way to be sure is by some careful measuring at a window or door jamb.

 

[mauro76]

Here is a picture I took by removing the cast iron air brick:

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• mauro76
• 1 Sep 2013
• 1

By the entrance door (take in account the plastering on the internal wall):

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• mauro76
• 1 Sep 2013
• 1

As seen by the bedroom wall (the measure tape is showing where the wall ends):

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• mauro76
• 1 Sep 2013
• 1

The bricks are about 220 x 63 x 105 mm, which I believe is the imperial brick size. This is consistent with the wall thickness.

As tony1851 mentioned, brickwork pattern is Flemish bond, and given the measuring I've made it's in particular a "Double Flemish bond of one brick’s thickness", which I believe is a solid wall:
http://en.wikipedia.org/wiki/Brickwork#Brickwork_with_courses_of_mixed_headers_and_stretchers

It's very cold indeed, catlad. Only insulation option is solid wall insulation, but the external one would deface the current half bricks / half rendered look, which is one of the reason we chose the house, and internal insulation would reduce the space. The insulation would be very expensive too.
Not an option for now

In time for this winter I would only be happy to repoint the bricks, and stop water and humidity.
Any suggestion in this direction?

 

[stuart45]

In the 30's lime mortar was often being gauged with Portland cement, so it may not be a true Lime mortar.

 

[mauro76]

stuart45, would you suggest to use a proper lime mortar?

Reading around, it could be that they did tuck pointing.

https://environment7.uwe.ac.uk/resources/constructionsample/Conweb/walls/solid/section3.htm
In some cheaper work tuck pointing was used to emulate the best construction. In tuck pointing the bricks (usually with uneven edges) were jointed in a mortar which roughly matched the colour of the bricks. The joint was then finished (pointed) with a very thin ribbon of lime and silver sand. From a distance it looks as if very good quality bricks and fine joints have been used. Examples of this can be found in the pointing section of Mortars.

https://environment7.uwe.ac.uk/resources/constructionsample/Conweb/walls/mortar/section7.htm
A few houses were tuck pointed (see below). The wall on the right (still the left-hand photo) has been re-pointed in a lime or white cement mortar.

 

[stuart45]

The pointing style is Weather struck and cut, common in the 30's. New work was raked out and pointed, often with white mortar, at the end of the job. Where yours has dropped out was not raked out deep enough.
It could well contain Portland cement. If it does re-point with a similar mix.

 

[mauro76]

Thanks stuart45!
On the other hand, I could decide to rake out and repoint at a deeper level, as other mortar could drop. In that case would you go for a lime mortar like NHL 3.5?

 

[stuart45]

I would only use NHL if the original is a lime mortar. NHL needs to be mixed up for much longer than cement mortar. 20 minutes in the mixer, then leave another 20 to fatten up. Needs to be kept damp and out the sun for a while.