Repairing cracked brick walls - Helical strips

[montyjohn]

I'm looking to buy a listed brick Georgian property with a brick (possible Victorian) extension, again brick.
The extension includes a Coach House, where the arch has clearly dropped at some point resulting in cracks on adjacent walls.
The survey suspected that some of the cracks could also be due to thermal expansion (old laundry boiler) but couldn't rule out a foundation issue, but the shape of the cracks didn't point to a foundation issue.

Looking at 20 years photos some of the external cracks were repaired a long time ago, so it doesn't appear to be new movement.

Cracks are parallel, vertical and up to half an inch.

Naturally the surveyor recommended getting a structural engineer out, but also to monitor.

Solutions could range from just filling with lime, or inserting helical strips.

If we go down the helical strip route do we need to avoid using the grout they provide. I believe this is epoxy based so will create a hard point and trap moisture.
We could lime them in, but I suspect this achieves very little.

Does this mean helical strips shouldn't be used on period properties?

Another thought, would helical strips trigger listed building consent?

 

[paulc]

If we go down the helical strip route do we need to avoid using the grout they provide. I believe this is epoxy based so will create a hard point and trap moisture.
We could lime them in, but I suspect this achieves very little.

The following is just my opinion..
If you use a lime mortar, the rods will be able to move a little within the mortar and any stresses will not be distributed evenly along the length. Using the epoxy grout, it will bind firmly with the bricks and rods and spread the loads out evenly. The grout should be recessed well within the wall, so there would be plenty of depth to point the joint with a lime mortar. The amount of moisture that could be trapped would be minimal - It is not as if you are pumping grout in between every brick in the house. At most, it would be one rod every four to six courses, and a length of about 1 metre. Hardly enough to cause problems.

 

[Flyfisher]

I've used those 'helifix' rods in a couple places. The first was in an external chimney stack that was added (not very sympathetically, I might add) to the C16 timber frame during a 'Georgification' of the house a few hundred years ago. It's brick construction but had clearly moved a fair bit over the years resulting in some large gaps and cracks between some of the bricks, many of which were loose enough to remove by hand! I suspected the movement and subsequent damage was historic so I rebuilt the worst areas and patched up the others using lime mortar and embedded helifix rods where I could before limewashing the lot. 10 or so years on the stack remains solid with no signs of cracking, though it's anyone's guess if that's because of the helifix rods, but I guess they are doing no harm.

The second area I've used them was to stitch across some long and fairly wide cracks in a rubble wall near a gable wall, again using lime mortar prior to limewashing. This has been less successful and some cracks have reappeared probably, I suspect, because the gable wall continues to move slightly. I wondered if the cracks appeared again because I didn't use an epoxy grout but I somehow doubt it because although I'm sure an epoxy grout would help distribute any built-up stress more widely within the wall, the rubble construction together with the fairly soft lime mortar means that it would still be fairly easy for the helifix rods plus epoxy grout to move within the wall. I find it difficult to imagine a few hundred tons of thick gable wall to be prevented from moving by a dozen or so helifix rods, but again, I guess they are doing no actual harm.

As for their use requiring an LBC application, I highly doubt and besides, how would anyone ever know? If the application required drilling holes or cutting into stonework and would leave visible marks then perhaps, but for invisible insertion within a bed of mortar I wouldn't bother with LBC.

 

[alexander]

its the resin is what makes them work, heli bars sealed into place with the resin then pointed up with lime mortar, they are fine in older properties generally about a mtr apart 1mtr long centred at the point of the crack in the wall,
depends on how strict your listings are as to if you need to apply for every repair listings will not come out and check, if listings are required you will also need building regs to sign the job of which makes a straight forward job a lot more expensive and slower,
different councils have different interpterion's of the rules
good luck