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Fill hairline cracks in exterior walls?

  • 06-04-2022 5:19pm
    Registered Users Posts: 1,212 ✭✭✭

    I have quite a few hairline cracks in my exterior walls. It had me concerned, with all the chat about mica these days. I've had multiple people (loss assessor, loss adjuster, mate who works in construction and finally a structural engineer) who all reckoned they were normal enough. Couldn't guarantee it wasn't mica without a test but nothing they would be concerned about at present.

    There are a few long horizontal on the gable on, at floor levels, so I think they reckoned it was due to the render stages or something. Some vertical and one stair stepped which has been on the house for years and doesn't seem to have gotten any worse.

    I still worry about it from time to time when I'm outside and see them! Anyways, I'm wondering should I get these filled? Would leaving them be result in them growing over time, say freeze/thaw if any water got in to the cracks? Or are they grand until I'm painting next? Some of the cracks seems to have moss or something growing in them which makes them look worse. I'll dig this out if I manage to get a decent ladder....

    All the neighbours will reckon we have mica if we get it patched 😄



  • Registered Users Posts: 757 ✭✭✭C. Eastwood

    Any Photos

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    No idea why they are showing upside down!

    edit: fixed

  • Registered Users Posts: 757 ✭✭✭C. Eastwood


    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?

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    No one mentioned crack monitors, or tests of any kind. We did have minor flooding the odd time after heavy rain. Some of the drains were unable to take the water away quick enough. We’re getting drainage redone. Water didn’t enter the house or anything but flooded back street. Would that cause movement?

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  • Registered Users Posts: 757 ✭✭✭C. Eastwood

    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.

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    I’ll have a look around to see who does that kinda work. Think I know one crowd. Is it an expensive job? Difficult enough tryin to find someone to sort the drains too. Plenty people who’ll dig a drain but want someone to assess the whole situation and figure out something that would solve any issues.

  • Registered Users Posts: 757 ✭✭✭C. Eastwood

    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.

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    Pretty sure we’re covered for issues caused by escaping water. When we had the occasional flooding I had wondered if that would causes it. At the time I checked coverage.

    Dont see any independent drain testing up here. Mostly down south but do cover nationwide. There are companies that do cctv check of the drains, mapping etc. Is that enough or does it have to be more thorough?

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    I’ll call a few of the places down the country that do hydrostatic testing next week. See what the story is. Depending on the company they might be able to recommend what changes need to be made to the drainage to handle more water.

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  • Registered Users Posts: 757 ✭✭✭C. Eastwood

    You must get a hydrostatic test carried out to show the amount of water leaking out and the location of the leak, if you wish to make an insurance claim for reinstatement of the house if the cracks are caused by escape of water from drains.

    Most insurers will not give cover for flooding in flood areas.

    Escape of water from pipes is not flooding.

    Only get advice from a Chartered Building Surveyor or a Chartered Civil Engineer in private practice, in relation to the drains and any potential insurance claim if there are leaking pipes adjacent the house.

    Underground leaking plumbing pipes could also cause the cracks in a house, which would also be covered by the buildings insurance

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    We’re not in a known flood area. Only happens once or twice a year after prolonged heavy rain that water from the fields behind the house comes down but our drains don’t seem to be capable of taking the water away quick enough.

    I’ll try and get someone out to do that test and take it from there. If they come up with nothing then it’s likely the drainage needs to be improved (we know it does anyways).

    I just want an answer as to the cause instead of “just further settlement”

  • Registered Users Posts: 45,982 ✭✭✭✭muffler

    I would think that (if the house was on level ground) your drainage system is probably adequate for the normal rainwater and accumulated surface water. But you do have have excess surface water coming from the adjoining field and I think thats the biggest issue.

    Id recommend getting the existing drains surveyed just to confirm. There are a couple of local companies that do this. If the drains are okay then you need to look at how best to divert the surface water coming from the field behind the house so that it doesnt flood the rear drive / yard.

  • Registered Users Posts: 757 ✭✭✭C. Eastwood


    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.

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    Yeah, the fact its a complex issue is my problem 😊 Doesn't seem to be a one stop shop person I can get to come out and answer this question. The few experts I've had take a look just told me that there was likely a bit of movement and the cracks were nothing to be concerned about, but it still does concern me. I don't want to leave it and end up with the house subsiding in future years. I'm thinking on ordering a few of those crack monitors and putting them on myself. I've actually spotted one drain which is quite useless, the incline is away from the exit point of the drain, so water wouldn't get drained from it!

  • Registered Users Posts: 10,904 ✭✭✭✭Furze99

    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.

  • Registered Users Posts: 39,228 ✭✭✭✭Mellor

    That's incorrect. Wall ties do not transfer vertical movement (settlement). There could be a settlement crack in one place in the outer leaf, and a settlement crack in another place in the inner leaf - or no crack.

    Settlements in the foundation is entirely normal. Doesn't require ground water issues. But that can also cause cracking and be an issue. There's no one solution and nobody can provide the answer via the pictures on the internet.

  • Registered Users Posts: 10,904 ✭✭✭✭Furze99

    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.

  • Registered Users Posts: 39,228 ✭✭✭✭Mellor

    Who said anything about the foundation settling on one side?

    The Foundation settles, one leaf above cracks at a random point 3m vertically above. The other leaf cracks at a different point. Or not at all.

    you are talking tiny movements

  • Registered Users Posts: 10,904 ✭✭✭✭Furze99

    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.

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  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    We do have cracks inside too but only 1 matching the outer leaf on the arch of a window. Most internal cracks are diagonal from doors. Few across ceiling. Engineer pointed out these were all normal weak points. Another not from a door is where there is a join with the en suite wall on there other side.

    We need drainage improved anyways so will get the existing drains checked along with it. As said above, I might stick one of those crack monitors on inconspicuous area.

    There are cracks that have been there for years but more seem to be appearing.

  • Registered Users Posts: 10,904 ✭✭✭✭Furze99

    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.

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    Dont know bout the stair stepped one as part of it’s a tiled bathroom in the other side (no signs on tiles) and wallpapered wall. That’s been there since we bought the house. Doesn’t seem to have gotten any worse.

  • Registered Users Posts: 757 ✭✭✭C. Eastwood


    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.

  • Registered Users Posts: 39,228 ✭✭✭✭Mellor

    The door lintel spans across both leafs which it why the crack is more likely to be transfer.

    Regardless, that isn’t evidence that counters anything I said. I never said it can’t happen, I said it does not have to happen if order for it to be a settlement crack. Which was what you claimed. Which is uninformed and misleading.

  • Registered Users Posts: 10,904 ✭✭✭✭Furze99

    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.

  • Registered Users Posts: 39,228 ✭✭✭✭Mellor

    Your post was simple incorrect. It’s not being pedantic to point that out.

    OP is worried about a serious issue. People speculating blindly is not really helping.

    @OP Slow running drains do not lead to cracks - that is caused by water leaving the drainline. Settlement craics are normal and not an issue. Those look similar to normal settlement cracks. But if you are in the NW, then consider a mica assessment. Nobody can advise about mica over the internet.

  • Registered Users Posts: 757 ✭✭✭C. Eastwood

    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.

  • Registered Users Posts: 1,212 ✭✭✭chris_ie

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  • Registered Users Posts: 1,212 ✭✭✭chris_ie

    Not sure whats going on but I can’t delete that previous post…

    Cheers for info folks. Don’t worry I won’t be using boards for an official diagnosis 😄

    Had a look at that drain I mentioned previously. It slopes away from the down pipe for the water so it wouldn’t escape. Down pipe on right. Slopes slightly in direction of red arrow. Muck etc on the bottom end and it would just be directing water towards the house.