Fill hairline cracks in exterior walls?

chris_ie

I would have a reservation in relation to these cracks.

The cracks are minor cracks, but apparently are caused by some movement.

You indicated that you had the cracks looked at by a Loss Assessor. Did the Assessor get a hydrostatic test (water test) on all your drains?. This is the first thing that must be done.

I have never visited the houses damaged by Mica in Donegal and surrounded areas, I have read about mica and seen various reports on same, therefore I’m not expert on mica.

The cracks in the photos appears to be caused by some minor movement in the walls.

I do not understand why the Loss Assessor did not fit Crack Movement Monitors on the cracks. (Sometimes called Tell-Tale crack monitors).

These need to be fitted and checked over a period of a year or more to ascertain if there is further movement or to ascertain if the movement has ceased.

Do you have correct home Building Insurance cover?

The existing drains should have been tested with a hydrostatic test ( water test) to ascertain if there is escape of water from them, and if there is a leak - the amount of water leaking out in litres per minute.

There should also be a CCTV carried out on all the existing drains to see the condition of the inside of the drain pipes

Can this be carried out now.

You should not allow any works to be carried out to the existing drains, until you have a hydrostatic test, and a CCTV carried out on all the drains.

Google Independent Drain Testing.

Cracking to the structure of a house can have many different causes.

One main cause is escape of water from pipes. Drains or plumbing pipes.

Structural cracking to a house, caused by water escaping from these pipes is usually covered by the Home Insurance Policy.

Get the drains tested first. If the drains are allowing water to escape, you may be able to claim some of the cost of the structural repairs from the Insurance Company.

If you interfere or remove the drains - you will be removing the very necessary important evidence.

Do you have correct Home Building Insurance cover.

chris_ie

This Is a very broad and complexed subject.

Settlement occurs for a period of time when there is a house approx 150 tonnes built on the foundations.

Settlement will stop after the load of the house meets equilibrium with the soil supporting the foundations, provided that the ground under the foundations has good bearing capacity all round. If the ground under a corner is softer than other parts, then further settlement will occur in one area and cause some cracking.

Water wetting and softening the soil under part of the foundations, may cause subsidence of parts of the foundations, which will cause cracking of the very brittle concrete block walls.

Sometimes this water is escaping from the drains or plumbing pipes adjacent to the foundations.

You mention cracks on exterior walls. What sort of construction method was used do you know? Standard cavity block wall or timber frame? If the former, the two leaves of blocks are linked/ stabilised together with wall ties, so you'd expect some corresponding cracks on the inside? That is if the whole foundation is settling, which is what is being suggested by queries on drainage. If a standard cavity block wall and cracks confined solely to outer leaf, might throw a different light on it. FWIW, we have a couple of settlement cracks between our extension and old build. I've painted over them but they tend to reappear. Not sure if it's further slight settlement or differential heating effects.

Surely with standard strip foundations, it's unlikely that one side of the foundation will settle and not the other. They'd only be c 1 metre wide? But re wall ties, I guess one might bend a bit, but surely they must stress the inside leaf as well. Anyway OP, any cracks on the inside.

Well I have a shed built as a cavity wall, after a year or so a wee crack appeared in the render by the door lintel, mirrored on the inside leaf. So going on empirical evidence, it does happen.

The stepped crack in your photo top left of window, maybe that appears inside? Never tried it, but wondering can you improvise a simpler type of check. By scoring or marking a narrow straight line across a crack, photograph it - you could include a scale - ruler with mm. Then monitor this over time. Obviously it would only crudely indicate relative movement between the sides of the crack and not some absolute where they both move together. But would give an idea and be cheap. No idea if this works but can't see why not at a crude level.

chris_ie

you mentioned that one of the experts said that the cracks are nothing to worry about. I disagree with that statement, and if you go to sell the house, the Surveyor carrying out a Structural Home Buyers Survey, will not give a favourable Report on the house.

you also mentioned obtaining crack monitors and fitting them yourself.

Crack monitors need to be fitted chemically and mechanically (glue and screws) and will need to be recorded over 4 seasons and photographed and recorded by an independent Surveyor or Civil Engineer.

it doesn’t matter what type of external walls, or wall ties - the external part of the wall of your house will be concrete blocks and there are minor cracks apparent .

The cracks in your house are possibly caused either by settlement or subsidence.

Foundations of houses are constructed and bear on top of the subsoil.

the bearing capacity of the subsoil can change in a site. In most dwellinghouses the bearing capacity of the soil is checked by visual and some simple tools by the Surveyor or Engineer, because Dynamic Probing and Window Sampling to ascertain the bearing capacity of the soil is expensive.

Sometimes there is no Professionally Qualified person to check the bearing capacity of the soil as the foundations are being excavated.

Unfortunately some times the bearing capacity of the soil is not the same under all of the foundation, and differential settlement may occur in some parts of the foundations caused by settlement, which will result in cracking in the concrete block walls.

You need to retain a Building Surveyor or Civil Engineer in Private Practice with PI Insurance to diagnose what is causing the cracking in your home. It is very complicated and requires various testing etc.

Well if you want to be pendantic, you can observe that.. The substance of my query was twofold: method of wall construction and are their cracks on interior as well as exterior walls. Both relevant to OPs query. The OP is worried about 'mica', my (limited) understanding is that this is most likely to cause an issue in exterior leaf as these blocks are exposed to more moisture. That's all.

Leaking drains adjacent to houses can and do cause wetting of the soil under the foundations which cause the foundations to subside near the leak.

this is caused by subsidence.

If the foundations subside a few mm then the inflexible concrete block walls and plaster will crack.

Many of these foundations are underpinned with piles and other necessary works.

Proving that the drains are leaking is necessary for to claim the most of the costs of the underpinning and reinstatement from the Home Insurance Company.

This is very complexed and it’s necessary to have a Building Surveyor or Civil Engineer retained.

this cannot be diagnosed by looking at photographs here. It requires a full survey of the property, and carrying out tests on the external ground adjacent to the damaged area etc.