Walls - construction and cracks

[Pford75]

We have an internal wall (looks like it was previously external), which has sufferred severe cracking in the plaster.

The wall is an absolute mish-mash of brickwork, clay-lump and a few bits of flint used as infills as well as the odd wooden beam lain between courses of brickwork!! It really does look a mess, with some fairly huge gaps and some very uneven courses....it also looks as if it has been built in two sections (with no bonding tie between the tow sections - ie. the bricks don't overlap).

Along this join, the cracks were pretty severe (enough to crack the lime plaster wide enough to insert a finger). We're prepared to have the wall replastered in lime, but wondered if there is anything we should have done to the wall before plastering?

 

[middi]

It has been there a long time and it is still standing.

My initial thought would be to stabilise the wall and any cracks and voids by repointing and replacing the odd brick or stone here and there as required and where necessary.

Then lime render the lot.

 

[Gervase]

A lot depends on the age of the cracks. If they've all appeared in the past six months, then you've got cause to worry. If it's more like the last six centuries, then less so.
If you've got a rip-joint between two bits of the wall you might consider putting in in some steel ties every foot or so and then repointing, but if the crack is ancient and shows little sign of recent movement (how much dust, junk and debris is in the crack?), I'd be tempted just to repoint and replaster and wait and see.
If the crack starts appearing again within the next few years, then have a think about sterner treatment, but don't put it at the top of your priorities list just yet.

 

[andrew gayton]

use a mixture of helifix to bed joints, gravity grouting and pointing up/dubbing out and replaster in a lime/crushed chalk and hair plaster - far more flexible than using sand as an aggregate and therefore more resiliant to cracking.......... easy peesy.

 

[Pford75]

Thanks - silly question I suppose....but what is 'gravity grouting'?

 

[andrew gayton]

where, after pointing the crack/fissure to a depth of say 25mm, you work up the wall in lifts of say 750mm pouring in a lime/pozzalanic grout via funnel and hosepipe to the top of the section.... point up the next lift and start again.... leaving a day inbetween each section or lift. pressure grouting is too extreme and can blow the face. tried and tested. i did my complete house in this way.... used approx 400 litres of grout (hydrated non hydraulic lime and brick dust, 1 part to 5 parts of water.