Brick re-pointing

[andrew29]

Hi,

I have a 1958 double brick house that needs repointing in the lower courses where I guess there has been more moisture than above the damp proof course.

The current mortar is quite powdery and is a light cream colour (see pic).

I have a pointing tool and have researched the approach but am hoping someone can suggest what the current mortar would be and how I’d go about matching colour. Eg am I better try to recreate a lime mortar (if that’s what it is), or coloring a std mortar mix?

The pic shows the original mortar, the gaps, and a test repoint I did with some mortar I got. Clearly color match is an issue right now.

Is it a lime mortar? Should I try and recreate? Or should I try and colour match?

Cheers

[andrew29]

75205AA7-A2D6-4EF7-9831-90BD27F271A2.jpeg

[rwbuild]

It is lime mortar.
Use yellow brickies and white brickies sand mixed approx 1/3 yellow to 2/3 white sand and standard off white cement at 5:1 ratio (5 sand, 1 cement) You may have to play with the yellow/white ratio to get an exact match, remember to let you test batch dry COMPLETELY before comparing (at least 5 days)

[andrew29]

Thanks Ray,

So even though its a lime mortar I should re-point with a cement mortar?

Ive read that lime mortar is a bit more forgiving for a beginner as it doesn't go off as quickly?

Cheers

[rwbuild]

A mix of 5:1 gives a working time of about 1.5 hrs before you have to wet it up again with water depending on ambient temperature. You can use CLEAR Bycol to prolong this

[aldav]

Surely an hour and a half at a time of squatting down pushing mortar into bricks would be enough for any sane person. Time to reward yourself with a little break.

[dinosour]

The lime mortar is softer than its cement equivalent. The mortar should be the sacrificial component not the brick. If you use cement you run the risk of the bricks fretting away and leaving a grid of cement.
If it is lime replace it with lime.

[Lappa]

My house is 1916 and had the same problem on the lower brick layers. It’s due to vehicle exhaust attacking the lime mortar.
i got an expert in to look at it and they said the same as dinosour - use lime mortar not cement.
Got a local old guy that specialised in that and tuck pointing to do it - not cheap but it look a couple of days. Very labour intensive - cutting out the old powdery mortar and replacing by small trowel but it looks great.

[Beardy]

My house is 1916 and had the same problem on the lower brick layers. It’s due to vehicle exhaust attacking the lime mortar.
i got an expert in to look at it and they said the same as dinosour - use lime mortar not cement.
Got a local old guy that specialised in that and tuck pointing to do it - not cheap but it look a couple of days. Very labour intensive - cutting out the old powdery mortar and replacing by small trowel but it looks great.

Did the “expert” tell you the car exhaust caused the problem? It is usually weathering or rising damp

[rwbuild]

Beardy is correct.
Lime mortar near ground level is not a good option. The weak cement ratio prevents fretting of the mortar.

[Lappa]

Did the “expert” tell you the car exhaust caused the problem? It is usually weathering or rising damp

The “expert” (why you put it in inverted commas is only known to you) is on a panel that consults on the restoration of heritage buildings. BTW the compounds in vehicle exhaust that accelerate the weathering are NOx and SO2 Which are also responsible for the deterioration of sandstone.

[Beardy]

Yes I understand that pollution will assist deterioration of a building over time but that is not going to give you hot spots of deterioration below the dampcourse like andrew29 is experiencing plus he is in a Tasmania so vehicle pollution is not of paramount concern like you might be experiencing in Sydney but even so that will be general deterioration not moisture or weather related.

Using lime mortar is best from a restoration point of view and to keep the building original but a weak cement based mortar is not going to do any harm just the same.
When cement was available the standard was to use a cement based mix up to the dampcourse and then traditional lime based mortar above DPC.

The comments about the mortar being the sacrificial component of the brick wall is technically correct and that still stands today with modern mortars using sand / cement so as long as you use the correct mix portions you will not cause a problem.

[Lappa]

Fair enough. All that was said was don’t use cement which may have meant a cement mix as now used?
I don’t know the exact mix that the guy used in my house but he called it a lime mortar mix and he had been doing it for eons.

Done about 15 years ago and still looks good and it goes right down to the foundation bricks.

D9F22C1D-8A95-444D-B5F2-778BB7C78709.jpg

[Beardy]

A structure of your era would of still been lime mortar to the footings and the remedial work you had done would most likely been repointed in the same fashion.