Cracking in brickwork where extension meets building, SUBSIDENCE??

[HKing]

Hi,

I am a new member here, in the process of buying a 3 bed 2 storey 1970's house and have noticed cracking in the masonry where the rear (single storey) extension meets the building. The cracks are stepped and go through both the bricks and the mortar. The extension itself is around 15 years old and done before the current vendors bought the house.

However, approx 3.5 years ago, the current occupants removed a load bearing wall (which ran in line with where the extension starts). A 5.77m RSJ was installed in its place, along with another smaller 2.29m RSJ bolted onto the centre of this RSJ (perpendicular, to form kind of a T-shape structure).

We have carried out a level 3 RICS building survey, however their only advice was to monitor the cracks for 6 months using digital calliper - Unfortunately we don't have this much time so I was hoping I could get some of your opinions on this. He also mentioned that he observed some of the insulation (using an acronym I forget) was also damaged behind the brickwork. He scared us by saying that remedial actions could be as far as underpinning needed if the cracks are progressive due to subsidence!? Thank you all in advance.

Photo of the cracking:

Snippet of the Surveyors summary:

Building plan for the structural works (removal of load bearing wall):

 

[^woody^]

Where are the cracks located on that floor plan?

 

[HKing]

Where are the cracks located on that floor plan?

The cracks appear to be directly under the RSJ. So the cracks start from approx 3/4 of the way up the side of the house, running up to where I imagine there RSJ sits, from there the cracks then further zig-zag diagonal up and to the right (ending by the pitched extension roof), if that makes sense? I will attach a rough drawing below...

 

[HKing]

The cracks appear to be directly under the RSJ. So the cracks start from approx 3/4 of the way up the side of the house, running up to where I imagine there RSJ sits, from there the cracks then further zig-zag diagonal up and to the right (ending by the pitched extension roof), if that makes sense? I will attach a rough drawing below...

View attachment 230919

Sorry, so to answer your question, it is where the rsj sits on the right hand side of that plan. (detached side of the house).

 

[HKing]

I also meant to say the cracking starts approx 1/4 of the way up the side of the property (not 3/4), sorry.

 

[^woody^]

There is a fan above the crack, and that fan can't be in line with the steel beam so the crack must be further along and not directly where the beam is, if so how much further out from the beam/original rear face of the house?

What about at the other side of the extension, any cracking there inside or out?

Is that crack in the photo much wider higher up or generally of even width?

Are there cracks to the internal plaster to ceiling and wall junctions anywhere else?

If a tiled floor, any cracks visible?

Is there a photo of the whole side elevation?

 

[HKing]

There is a fan above the crack, and that fan can't be in line with the steel beam so the crack must be further along and not directly where the beam is, if so how much further out from the beam/original rear face of the house?

What about at the other side of the extension, any cracking there inside or out?

Is that crack in the photo much wider higher up or generally of even width?

Are there cracks to the internal plaster to ceiling and wall junctions anywhere else?

If a tiled floor, any cracks visible?

Is there a photo of the whole side elevation?

Thanks for your reply -

No visible cracks on the other side of the extension, the outside is not visible as it's attached to next door house (the house is a semi).

The cracks seem to be generally even in width.

There are no cracks on the other side of this wall internally, but I suspect there may be plasterboard over the wall since it has a fancy kind of brick effect tiling (shown in picture below)

Picture showing the extended kitchen, the cracks are on the other side of the brick effect wall shown:

There are also some cracks in the bathroom above where the supporting wall was (I suspect due to poorly placed acros?):

I don't have any more photos of the side wall unfortunately but I managed to find a full side profile on google maps:

 

[^woody^]

What your surveyor should have mentioned is that extensions should not be tied into the house like that is, but should be tied with a metal tie that allows for movement of the extension - a flexible vertical joint.
This would mean that cracking like that is common when extensions are tied in like that, and although it's not the only possibility, he should have mentioned it being incorrectly built and a possible cause.

It's also a nonsense to advise some on-going monitoring for a crack in a home buyer's survey, when what you as a buyer want to know is whether to buy the place or not, and not that a crack needs to be monitored before any sort of opinion can be given.

But too many surveyors nowadays are either unable or unwilling to commit to any definite opinion, and will almost always shy away from telling you what you want, or more crucially what you need to know.

It comes down to assessing what cause is more likely than any other cause, and without making this an even longer post and going through all the reasoning, it seems that that crack is typical of horizontal movement and as such more likely to be related to contraction of the bricks, than anything else.
This is not a significant structural issue and a very easy and cheap repair.

• It's in the right place
• No movement joint
• Evenness of the crack
• Crack in just the external bricks.
• The mortar looks a very strong mix
• Looks like an old crack
• Crack largely following the mortar joints

It does not appear to be related to the beam (those cracks above it appear to be installation quality issues), although that’s not the say that the beam is OK – you need to do the normal checks to satisfy yourself that it was designed and installed correctly.

However, there may well be some other factor not mentioned here which means that some other cause then becomes more likely, and so you really need someone to re-survey and comment specifically on this. I think it’s worth pursuing, and whilst I doubt that anyone will actually put their neck on the line and say “this is the cause, 100% sure”, if they follow the correct reasoning process they will come up with a most probable cause, and then you will be in a better position to assess the risk.

Instruct a structural engineer, tell them to comment on the beam and the wall, and you don’t want any long term monitoring or investigation suggestions, just an assessment of possible and most probable causes, and remedies – and costs.

Tell them to take a ladder, a level and to knock the neighbour’s door for a look at that side

Then you can decide whether to negotiate a reduction in the selling price or walk away.

 

[HKing]

What your surveyor should have mentioned is that extensions should not be tied into the house like that is, but should be tied with a metal tie that allows for movement of the extension - a flexible vertical joint.
This would mean that cracking like that is common when extensions are tied in like that, and although it's not the only possibility, he should have mentioned it being incorrectly built and a possible cause.

It's also a nonsense to advise some on-going monitoring for a crack in a home buyer's survey, when what you as a buyer want to know is whether to buy the place or not, and not that a crack needs to be monitored before any sort of opinion can be given.

But too many surveyors nowadays are either unable or unwilling to commit to any definite opinion, and will almost always shy away from telling you what you want, or more crucially what you need to know.

It comes down to assessing what cause is more likely than any other cause, and without making this an even longer post and going through all the reasoning, it seems that that crack is typical of horizontal movement and as such more likely to be related to contraction of the bricks, than anything else.
This is not a significant structural issue and a very easy and cheap repair.

• It's in the right place
• No movement joint
• Evenness of the crack
• Crack in just the external bricks.
• The mortar looks a very strong mix
• Looks like an old crack
• Crack largely following the mortar joints

It does not appear to be related to the beam (those cracks above it appear to be installation quality issues), although that’s not the say that the beam is OK – you need to do the normal checks to satisfy yourself that it was designed and installed correctly.

However, there may well be some other factor not mentioned here which means that some other cause then becomes more likely, and so you really need someone to re-survey and comment specifically on this. I think it’s worth pursuing, and whilst I doubt that anyone will actually put their neck on the line and say “this is the cause, 100% sure”, if they follow the correct reasoning process they will come up with a most probable cause, and then you will be in a better position to assess the risk.

Instruct a structural engineer, tell them to comment on the beam and the wall, and you don’t want any long term monitoring or investigation suggestions, just an assessment of possible and most probable causes, and remedies – and costs.

Tell them to take a ladder, a level and to knock the neighbour’s door for a look at that side

Then you can decide whether to negotiate a reduction in the selling price or walk away.

Thank you Woody, this is a really thorough and logical response - quite refreshing to speak to someone with such an approach. I totally agree with your point regarding surveyors nowadays, I would have thought the title of the inspection being a 'homebuyers' survey should indicate that the survey is for the purposes of purchasing a home, therefore limited time to investigate!

I was worried at first because 'technically' the cracks do only begin from 1/4 of the way up the wall (which I was told may suggest rotation) and they do start off thinner at the bottom, but after half a metre or so from where they begin, the cracks are pretty much uniform in width the rest of the way up.

I'm not sure how you can tell how the extension is tied in? (but thanks for the heads up). I will certainly instruct a separate structural engineer to look into the points you made above in more detail. Many thanks again for your opinion, I've made a note of everything and will update when we've had a second opinion.

 

[^woody^]

I'm not sure how you can tell how the extension is tied in?

The bricks are toothed in, and this is inflexible as any addition to an established building will move.

Rotation of the extension or even any vertical movement of the rear extension foundation is a possibility and is not un common, but there would be several other visible factors which don't appear to be there. They may be on further inspection in which case that could become more probable. A very simple check is just looking along all the brick courses or checking with a long level all the way up the wall.

 

[HKing]

Just an update for those interested - I instructed a structural engineer to inspect and produce a report. The engineer came to the conclusion that it was due to the extension foundations settling (due to point loading downward force caused by RSJ). This uneven settling caused the cracking between the extension and the property. Thanks again for your guidance on this.

 

[jeds]

This looks like a case of somebody trying to be clever by toothing the extension into the existing building, when a flexible wall-starter joint would have been much more appropriate.

 

[timsterboss]

Hello, I was wondering if you managed to negotiate the price or pulled out ? We are in a similar situation and not sure what to do, thanks.