Repointing a Victorian house

[Tony Fisher]

This is a semi detached Victorian house. The bricks at the back half of the house are not too bad and I think after various changes it was repointed maybe 30 years ago. The front section though is very poor with soft red bricks, some of which are crumbling. Mortar is completely gone between a few bricks and gaps and cracks (up to 10mm) have opened. There's a corner of stronger bricks though mortar is still missing. This corner seems perfectly straight so I am not sure if there's structural issues or simply neglect of the brick work.
I have very little money to spend on it and will tackle it the best I can. Before winter sets in I am filling the deep holes with that mortar in a tube stuff as an emergency measure to stop it getting worse. Then my plan is to rake out the old mortar and repoint using 1 part Portland cement, 1 part hydralime & 5 to 6 parts sand in the Spring. This plan comes from reading various things online since I have no knowledge beyond that.
One photo shows the wall in 2012 but it is partially covered in vegetation. It was only when this was completely removed that the gaps and cracks became so obvious. Any tips / advice would be welcome thanks.

 

[Cubist]

As often happens the culprit is hiding in plain sight. You may perhaps be aware that in ancient times the large stones used to build things like the Pyramids were quarried using the technique of hammering dry wooden stakes into a series of holes drilled in the rock and the wooden stakes then soaked with water. The expanding wood then exerted pressure on the walls of the holes causing it to crack and break apart along the line of the holes.

I'm afraid that your offender in this case is the plant that has happily grown clinging to your house and exploited every foothold to increase its height and width. If this was a deciduous shrub such as wisteria then every year it would, in autumn, draw its sap back to the root bole and in the spring begin sending it back out with new vigour. Each year then, the extant roots that have penetrated the wall in previous years will grow larger and exerted new and additional pressure to shift individual bricks or, through such stresses, cause some to fracture. Here's the thing; unless you kill the root bole it will come back - you need to be very sure it's dead.

Evergreens such as ivy are equally, if not more pernicious and damaging.

In terms of rectifying the damage. Some of those bricks will likely be loose and even capable of being pulled out of the wall. They must all be removed and re-seated in fresh mortar to establish the structural integrity of the wall. Small gaps may be capable of closure with a simple re-pointing exercise. However, in all instances you will not know the degree to which the root structure has penetrated the wall and as a consequence, unless it is (forgive the pun) rooted out, there is a risk that as the root fibres continue to degrade there may be further movement in the wall.

Sorry that my outlook is not very encouraging but I think this is not a job for an amateur and some professional advice would be sensible.

 

[Stevers]

In defence of Wisteria - you'd need a heart of stone to get rid of these two, which are both layerings from the ancient Wisteria that grew against the garage of the family home:


There's a huge difference between plants that cling (Ivy, Virginia Creeper, some Hydrangeas) and plants that require support (Roses, Wisteria, Clematis). Within plants that cling Ivy is particularly damaging to fabric, Hydrangea not nearly so much, and Virginia Creeper is just stupidly vigorous.

I have planted a variegated ivy against our boundary wall to the road, but only after I'd repaired and repointed both sides of the wall, and in the knowledge that variegated plants have less vigour. To my mind this planting greatly enhances our little 'courtyard' and adds habitat. This was two years ago and it's up on top of the wall now, and at the stage where I have started to limit it's travel.

 

[Cubist]

Where almost any form of gardening is concerned I am more than happy to bow to the superior knowledge and expertise of others. As the First Lady would be happy to tell you, ALL my forays into such activities are limited to those aided by a brush cutter, chainsaw or billhook. That said, I have been allowed to help, when directed, with some heavy shovel landscaping but sadly only rarely at the controls of a JCB.

 

[housegolem]

My brickwork trauma was caused by masonry bees, especially on the more sheltered north facing walls. The top 8 or so courses of lime mortar had been damaged upto 80% of the brick depth, you could easily rake out and remove bricks or push the wall inwards. This sounds bad but it gave me an idea of how well a brick wall works in spreading load.

I wouldn't be too concerned about it falling down in a hurry

Other than the plants - the large vertical crack may have been formed by the not completely staggered brick bond ( each brick overlayed down the middle of the lower one) yours has a weird mix of a long flemish bond and not well staggered stretcher bond- is it an early cavity wall?

If its lime its lime i'd replace with lime as the mortar should always be softer than the brick.

 

[Stevers]

It's in Flemish Garden Wall Bond, though the pattern breaks down when it gets to the gable end. Headers are still visible so probably not a cavity. Wall ties in early cavity walls can be a problem, so that could be a blessing.

There are cracks across the ends of some of the bricks breaking the bond, which is not so good. Vertical cracks normally suggest spread, and diagonal cracks settlement. As it's all happening high up it could be that the roof is spreading and the diagonal crack more to do with that. Replacing slates with heavier concrete tiles can cause a roof structure intended for slates to sag at the ridge and spread at the eaves.

The movement so far can't be more than a few millimetres, and in the short term just needs monitoring, but it does require investigation to determine the cause and possible remedies.

 

[stuart45]

I'd agree with Stevers about looking for the cause to start with. As there's a tiled roof just below it's possible that the wall below was a knock through, and a beam installed. This would increase the weight on the ends of the wall, which could have caused the crack.
When a crack goes through the bricks as well as the joints it generally means the mortar is too strong. The only real exception is a heavy point load from above. Therefore, I would think twice about using a 1/1./6 mix for repointing on an old wall with soft bricks.
A problem with filling in cracks in walls called racheting has recently been brought to the trade's attention. Masonry walls are constantly expanding and contracting with temperature changes. When a crack is filled in with a strongish mortar the wall can't contract and close the gap. As it expands again dirt enters the gap over time so the crack gets bigger and eventually the joint starts to fall out. It then gets filled again and the same thing happens, which increases the size of the crack.

 

[Stevers]

It would be interesting to know if any movement is visible inside.

 

[stuart45]

There should have been, but you often find that people are more likely to fill up internal cracks. External cracks can be virtually invisibly repaired, but it does take a lot more effort.

 

[Cherryburn]

I would also caution against using cement mortar in an old solid wall. Not only does it risk creating issues with damp (introducing an impermeable barrier in a vapour open system), but it's also likely far too hard for the fairly soft bricks. You want the mortar to be softer than the bricks or else you'll have issues with spalling and cracking, and it'll be near impossible to remove and replace it later without further damage. If you must DIY something as a stop gap, consider an NHL mix, probably 2. It's pretty similar to cement in how it behaves and sets fairly quickly, but softer, flexible and breathable. Make marks on either side of the crack that you can measure to see if there's any changes.

As for the cause, if you have access to the attic it might be worth having a look to see if anything's obviously amiss. There are likely roof purlins bearing onto the wall, if there's any signs of movement underneath them that could point to an issue. There may also be something going on with that window you can see in the 2012 photo, that's almost certainly a later addition which may not have a proper lintel, or may have shifted something when it was installed. The plants are your most likely culprit, but you want to rule out more serious structural concerns, especially if there's still movement going on.