Reason for serial horizontal cracking?

[borderfox100]

Hi. Firstly as background to the problem, some pics;

South Facing Gable Wall - which takes full force of the wind.
Close-up - Gable Wall Crack1.
Close-up - Gable Wall Crack2.

Internal Surface of Gable Wall - Front Room
Internal Surface of Gable Wall - Kitchen/Diner.


The following pics 9 months later - Back and Front Walls
Back Wall - between neighbouring properties (semi-d's).
Back Wall - between bedroom windows
Front Wall - 2x Vertical Cracks - running directly beneath box room window.

The internal pics and those of the Gable wall were taken 9 months ago. They have deteriorated since then.

Summary of investigation into issue thus far
The property is a semi-detached - built 2005/6. It's subject to a 10 year structural guarantee - and I'm trying to claim via that guarantee.
Initially, the diagnosis via an engineer I retained was defective rendering. I've been fighting with the insurance company for 9 months and they say that they accept liability (verbally - I've asked them to put this in writing - specifically what they are taking responsibility for and how they intend to address the problem).
As is the nature of insurance companies, they have not made this easy! They initially claimed that the render even if defective was not responsible for water ingress all the way through to the inside of the dwelling! They made me prove that. I had two 2x1 sections of the outer leaf removed;
Gable Wall with outer leaf section removed.

It showed that bonded bead insulation had been used. I live in an area that the Agrement Certificate for bonded bead says is 'severely exposed' in terms of driving rain - and that under such circumstances, the product may be used IF the wall is rendered. The inference is that if the render is not watertight, the bead will conduct water as the bead itself is filling the cavity - and the whole point of the cavity is to prevent water ingress.

Secondly, a cable tie was exposed as part of that process - and found to have a complete mortar snot all along it from outer to inner leaf - acting as a cold bridge and definitely conducting water.

The bead itself was wet to the touch when we removed it.

My cause for concern right now is that I find it difficult to believe this is simply a rendering issue. Nobody - professional or otherwise - can explain to me how the wall could be rendered so badly as to result in uniform horizontal cracking like that (with the exception of that one instance of vertical cracking at the front of the house).
The only 'supposition' their engineer and my engineer could make was that the plasterers plastered the house in stages. This didn't sound plausible to me - and I asked a couple of plasterers if this was possible - they say it would never happen. I then managed to find someone who worked on the development as a labourer back then. He told me that they were plastered in one hit - as you would expect. It's important to note that these horizontal cracks are visible (to greater or lesser degrees) on ALL gable walls in this development of 30 houses. I asked him about the cracking and he believes its due to subsidence - as the complete site was filled and raised immediately before it was built on. He showed me the back of another house in the development - and pointed out an area where the ground has sloped away.

I have reason to believe that my own engineers views cant be trusted (due to professional links with the engineers the insurance company are using). Therefore, I'm trying to at least figure out as much as I can myself before engaging another professional.

Does anyone have any thoughts on specifically what type of damage this looks like? Does anyone have any ideas as to what steps I could take to investigate the actual cause at this point?

If it is subsidence, I have another difficulty in that the insurance policy includes this exclusion;

"Loss or damage caused by or consequent upon subsidence, heave or landslip unless such loss or damage is as a result of a defect in the design, workmanship, materials or components of the Structure of a Housing Unit."

The foundation is a raft foundation rather than strip foundation. Other than one small internal crack, there is no other evidence of cracking on any internal wall or floor surface.

If it is subsidence, the only way I can get this covered is to prove that the design of the raft (and my understanding is that a raft has to be engineered to suit the individual circumstances - and in this case, a site that was substantially backfilled) was inappropriate for site conditions.

Naturally, I will need professional help but before that, I need a better understanding of the scenario myself. I've already been led astray once already.

 

[^woody^]

How old is the house?
What is the construction?

Those cracks are not indicative of subsidence in any case.

 

[borderfox100]

How old is the house?
What is the construction?

Those cracks are not indicative of subsidence in any case.

House built in 2005/6 - so 10 years + built.

Construction is standard block - inner leaf - outer leaf with approx 100mm cavity filled completely with bonded bead insulation (not rigid insulation). Like this BUT outer leaf with same block as shown here for inner leaf. Rendered finish. Concrete raft foundation rather than strip foundation. The development site was raised considerably immediately prior to foundations going in.

If it's not subsidence, then what else can I investigate as regards what it is exactly? Can it still be an issue with the raft foundation? Someone suggested that it looked like a classic case of wall tie failure but the wall ties didn't look corroded (and they're only 10 years old) on the couple that were evident having taken out the section of outer leaf. I guess it could also be a case of badly placed wall ties or no ties in places - but would they have done this on EVERY house?

Bear in mind the whole time - that this appears on ALL gable walls in the estate - mine appears much worse simply because it takes the full force of high winds and driving rain.

 

[theprinceofdarkness]

A point not mentioned, is the render hollow in parts? If you put a ruler across a crack, has one side moved out? I do not believe that the whole rendering operation as done "in one hit", did they not stop for tea or lunch? How hot was the weather?
Its just that blocks should not change their shape and render when it has gone off should not either. So due to differential settlement of the materials, something has changed, was the render too hard and unable to cope with the mortar courses compressing? Theoretically it should be softer then the blocks and mortar.
Frank

 

[borderfox100]

A point not mentioned, is the render hollow in parts? If you put a ruler across a crack, has one side moved out? I do not believe that the whole rendering operation as done "in one hit", did they not stop for tea or lunch? How hot was the weather?
Its just that blocks should not change their shape and render when it has gone off should not either. So due to differential settlement of the materials, something has changed, was the render too hard and unable to cope with the mortar courses compressing? Theoretically it should be softer then the blocks and mortar.
Frank

I just did a recheck right now.

Pic1
Pic2
Pic3

Apologies - not the greatest of pics. I tried knocking each side of the crack, on the crack - didn't 'seem' hollow to me. I guess that's not the worst crack - the most blatant is at a height.
The second pic - there might be some difference between above and below the crack?...but it's subtle and didn't seem that noticeable to me (albeit mine being the untrained eye).

Here's the thing though. A row of 15 houses would have been plastered all more or less in the one 'job'. The other row of 15 would have been a good few weeks later. The same issue is evident each side. I mean - I know nothing about this sort of stuff (albeit I'm trying hard to understand!) but if it's due to work practice rather than something else, they did this the same way both times - on ALL houses?...or could there have been an issue with materials used?...or does the answer simply lie elsewhere?

 

[theprinceofdarkness]

If you think of a thick sheet of rubber that represents your block wall, then you paint it which represents your render. Now stretching the rubber would cause cracking of the paint, so have your walls got taller (not wider !!) or the render shrunk but only vertically? If you bend the rubber away from the paint, the paint would crack in straight lines, are the walls still plumb? You would not get the vertical cracks under the window. If you compressed your rubber wall, the surface would go all wavy with the paint cracking horizontally on the outside of the waves. Don't ask about the vertical window cracks. This is what I think has happened, if the rendering was all done in one hit, perhaps the blockwork was done in lumps. Each time they started, the first horizontal mortar course dried out too quickly, leaving horizontal areas of a different strength, now after 10 years these courses have shrunk by perhaps .1 mm, but enough to put excessive strain on the render which has cracked. But I would have thought that the render would be levered of the wall, and sound hollow.
Frank

 

[borderfox100]

If you think of a thick sheet of rubber that represents your block wall, then you paint it which represents your render. Now stretching the rubber would cause cracking of the paint, so have your walls got taller (not wider !!) or the render shrunk but only vertically? If you bend the rubber away from the paint, the paint would crack in straight lines, are the walls still plumb? You would not get the vertical cracks under the window. If you compressed your rubber wall, the surface would go all wavy with the paint cracking horizontally on the outside of the waves. Don't ask about the vertical window cracks. This is what I think has happened, if the rendering was all done in one hit, perhaps the blockwork was done in lumps. Each time they started, the first horizontal mortar course dried out too quickly, leaving horizontal areas of a different strength, now after 10 years these courses have shrunk by perhaps .1 mm, but enough to put excessive strain on the render which has cracked. But I would have thought that the render would be levered of the wall, and sound hollow.
Frank

I'm away from the house now - but will recheck again re. if walls are plumb (i'm pretty sure I checked before - but will recheck just to be sure).

I can see the logic in what you've explained above - thanks for the clarity of the explanation (makes it understandable to a non-builder type like me!). Notwithstanding that, would this not then be a very common problem for cavity wall /rendered finished constructions? The reason I ask is that it has so many people scratching their heads whenever I show them pics of it. I'd imagine that it would be quite normal to do the blockwork in several 'lifts'. In fact I (very briefly!!) laboured for a blocklaying crew back in the day. From what I recall, it would be normal to start/stop blocklaying.
I guess the mix could vary but then surely it would be a more common problem?

The source of the blocks themselves could have been changed but again, what's the likelihood of this having happened not only on the first row of 15 but again later on the 2nd row of 15?

 

[stuart45]

Always difficult to be accurate from a photograph, but there are a few common reasons for cracking. Wall tie rusting is one, but unlikely in your case as it was the old thick twist type ones which caused the problem. A sulphate attack can cause the joints to expand and crack render, especially where the wall is exposed.

 

[borderfox100]

A sulphate attack can cause the joints to expand and crack render, especially where the wall is exposed.

Is there any way I can investigate this to rule it in or out?

 

[stuart45]

You would have to cut some render away to look at the joints, and see if they are affected.

 

[^woody^]

Those cracks are not from foundation movement, or structural building movement and certainly not differential settlement of drying mortar joints - which is not even a possibility.

As the cracking affects every property, then it is either a workmanship issue - how the houses were constructed, and or a specification/material issue - poor or incompatible materials.

If you had not said that the houses were 10 years years old, I may have guessed at more like 110 years old. The render is shockingly bad, as are the cills and window surrounds, and the bargeboard is abysmal - those cuts! This might give a clue to the cracking - they were just poorly built.

From the limited images posted, the cracking seems random. Any sort of diagnosis should really look at all the properties to see if there is a pattern. I would not expect wall tie corrosion failure in modern times and in such a short time frame, but you never know. Checks would include if those cracks are on the same course as ties. If so, then the ties need to be looked at, in terms of the type, suitability and the quality of the work in building them in.

Shrinkage of the panels is possible, and the time of year when built, and the dampness of the blocks before being laid or afterwards could be a factor. As would mixing different blocks or bricks.

Some of the cracks are so close together, that it seems unlikely that stage plastering could be a cause. Not impossible, but just unlikely given the pattern.

Sulphate attack is possible, but should be unlikely in modern times. But if the cracks are widening over time,then sulphate expansion can cause this. The masonry would need to be sampled in a lab from a core sample, which would detect high sulphate content.

TBH, there are several possible causes, and I don't think that there are any more than already mentioned here. It does need a better investigation than what seems to have been done, and a comparison of all the properties and crack locations and some material sampling would be a start.

 

[stuart45]

If you had not said that the houses were 10 years years old, I may have guessed at more like 110 years old. The render is shockingly bad, as are the cills and window surrounds, and the bargeboard is abysmal - those cuts! This might give a clue to the cracking - they were just poorly built.
.

I would have thought older, especially as it looks like there is a Hopper head on the back wall.

 

[jeds]

This has none of the signs of subsidence or structural failure. My guess is poor materials, poor specification and poor workmanship. I would have the mortar analysed to make sure it is reasonable ratio of cement:sand, that the sand was clean and that it doesn't contain anything it shouldn't. Also the render; what material is it and is the mix correct? You appear to have some degree of water ingress and that shouldn't be the case in a 10 year old cavity wall. It may be inappropriate specification of the cavity fill or it may just be crap blockwork - or of course it could be a combination of the two. Unfortunately for you, cases where several factors combine to create a bigger issue are often difficult to pin down.

 

[borderfox100]

Thanks all for your contributions - it's certainly giving me food for thought in trying to get to the bottom of this enigma.

Struggling to get my mits on something that would act as a suitable straight edge. I ran a plumb line from the cill of the bathroom window on the gable wall down to ground level. Cill ledge was 60mm out from rendered finish. Set the end of the plumb line 60mm out from rendered finish at the bottom secured with a block. Even though line was taut, I find it very difficult to take an accurate reading - but when I hold the spirit level, at worst, the bubble may be veering towards or on the line (out of centre - indicating that the wall *might* be leaning outwards as it goes up). I;m not sure first of all if this is accurate and second of all even if it is, is it so much so that it's significant or insignificant. Perhaps I'd fare better with one of those in-line 'bubble' levels? That wasn't taken the full way up to the apex of the wall - nor was it thru an area of major cracking.

Those cracks are not from foundation movement, or structural building movement and certainly not differential settlement of drying mortar joints - which is not even a possibility.

Ok, well at least its good if that can be ruled out.

As the cracking affects every property, then it is either a workmanship issue - how the houses were constructed, and or a specification/material issue - poor or incompatible materials.
If you had not said that the houses were 10 years years old, I may have guessed at more like 110 years old. The render is shockingly bad, as are the cills and window surrounds, and the bargeboard is abysmal - those cuts! This might give a clue to the cracking - they were just poorly built.

I'll have to apologise in advance as you're dealing with a building ignoramus unfortunately

I assume you are referring to the left hand corner of the bargeboard on the gable wall - where cuts are visible. What is the effect of these cuts? Should they not be made or do they seem defective? What is the potential consequence of defect in this instance?
The same question re. the cills and window surrounds. How should they be? How do these relate to the cracking issue?

Those cracks are not from foundation movement, or structural building movement and certainly not differential settlement of drying mortar joints - which is not even a possibility.

Ok, well at least its good if that can be ruled out.

Any sort of diagnosis should really look at all the properties to see if there is a pattern.

Pics of other properties in the development.
Pic 1
Pic 2
Pic 3
Pic 4
Pic 5
Pic 6
Apologies for the quality - taken this evening in poor light - and I didn't really want to draw the attention of the neighbours! I could provide many more examples - this is just a selection - but it shows the EXACT same pattern. Mine is much worse for 2 reasons;
1. The main reason being that I'm at the end of the row - and my gable is taking a serious hit from winter winds/severe driving rain.
2. Some have painted over - I'm well overdue a paint job - but I wanted to monitor this situation - so wasn't and won't paint until the situation is resolved.

I would not expect wall tie corrosion failure in modern times and in such a short time frame, but you never know. Checks would include if those cracks are on the same course as ties. If so, then the ties need to be looked at, in terms of the type, suitability and the quality of the work in building them in.

Wall ties are quite young - just 10 years. One has been exposed (albeit not in a place where there was horizontal cracking - and it looked fine in terms of integrity => wall tie
Are there not ties on every row of blocks?

Shrinkage of the panels is possible, and the time of year when built, and the dampness of the blocks before being laid or afterwards could be a factor. As would mixing different blocks or bricks.

Shrinkage of the panels?...as in the blocks themselves?? Can this still be the culprit even though each row of houses were built a few weeks apart?

A sulphate attack can cause the joints to expand and crack render, especially where the wall is exposed.

Sulphate attack is possible, but should be unlikely in modern times. But if the cracks are widening over time,then sulphate expansion can cause this. The masonry would need to be sampled in a lab from a core sample, which would detect high sulphate content..

Well, I'm in Ireland - and this 'development' was built in the middle of a major building boom/housing bubble - they couldn't build them fast enough - and building regs were rubbish. As for oversight and inspection, a complete joke!
Added to that, the mention of sulphite....there have been major issues with pyrite and mica contamination - that has lead to some poor people with houses that are worthless. This tends to be regional and revolve around certain quarries/sources. There have been cases an hour from here. Problem was (the now defunct) developer was also in the quarry business(sand and gravel only) and was bringing in fill from places I simply don't know of. If it was an issue of that nature ...where to start? Test the blocks, test the raft material (and if I do that, I have to puncture the founds and the damp proof course) - sample the infill upon which the houses were built??
I definitely don't have the classic pyrite/mica contamination effect going on - i.e. crumbling blocks or internal cracking (there's virtually no internal cracking bar one small example) but I suppose it could still play a part if one single source of one element was contaminated?

My guess is poor materials, poor specification and poor workmanship. I would have the mortar analysed to make sure it is reasonable ratio of cement:sand, that the sand was clean and that it doesn't contain anything it shouldn't. Also the render; what material is it and is the mix correct?

There are a good few options for analysis of materials -and those tests are well expensive. Anyone care to prioritise them - and do so based on the following update also?

Since posting - after 9 months of fighting with the insurance company (structural insurance - not regular/annual house insurance), I upped the anti with them and told them I was adamant I was going legal with this. They now say they accept liability for my claim. They don't say specifically what remedial action they are proposing - but meeting on site to determine that. Now, here's my conundrum...

When I started out with this, I was thinking in terms of defective render. I'm worried that it may be more serious. If I accept what's on offer, you can be sure they will insist that this is a 'full and final settlement' with no come back. What I'm concerned about is that there's something more fundamental at play - and that wall (or walls) are not structurally sound.

In light of all of the above, what do people think I should check first in terms of testing, etc? What remedial action would you be satisfied with at this point? I'm assuming they will suggest re-render. IF theres no chance of that wall coming down - or the same thing repeating itself, I'd be happy enough with that...but what confidence can I have in that?
Should the bonded bead insulation stay (is it fit for purpose in this location/wall build up AND has it been contaminated due to the water ingress in any case) - or should I press for an alternative eg. rigid insulation and/or external insulation? How does the presence of mortar snots on the wall ties feed in to this scenario?

 

[jeds]

I think I'd remove a section of the internal leaf in a location where dampness is at its worst. Similar to the section in one of your photographs which I assume is external. This ought to tell you how the dampness is tracking across the cavity. Having said that, as long as you can rule out dampness coming down the cavity from above - i.e. from the roof eaves, we know it isn't leaping across thin air so it's either the wall ties or the cavity fill, or both. If it's the cavity fill it needs to be cleaned out. If it's the wall ties you can't clean them with the cavity fill in place so it still needs to go. Can you see where this is going? Next question is how easy will it be to remove the cavity fill? You are looking at cutting out blocks every X distance apart and raking the fill with a hook and vacc'ing it out. You knock the snots of the ties at the same time. No small job and depends how well the fill is bonded? After that you need to replace the cavity fill or have an alternative - like external wall insulation. What sort of money are they talking about. I don't think you'll get this done for less than £25k. Maybe more.