Internal and External Cracks in 8 year old single storey extension - due to pile-driving?

melb

hi there i will try to keep this short and to the point,

We had a single storey rear extension built in 2017/2018 and K-Rendered externally along with bi-folds and windows supplied and fitted by well known reputable company.  Everything was completed to our satisfaction.

A construction site is ongoing at a lower level, canal side, very near our house (1990s built detached) only probably 30 to 40 yards away but at about the same depth if that makes sense. We are at the top of an old quarry and the site is at the bottom.

When pile-driving took place in summer 2023 our floor was vibrating, ornaments were rattling and I informed the PR man at the construction company that I was putting him on notice that any damage to our house we would be in touch. He had been round as building started and said get in touch if any problems.

We then started to notice cracks inside and outside the extension and these have worsened in the last couple of years.  The cracks are at most about 2-3 mm wide so not horrendous but they are only on the side nearest to the construction site.

A representative visited shortly after the pile driving and told us to monitor it and then a second person came out in January and has finally sent us his findings which are that basically it's nothing to do with them.

This is his report

Following my inspection, I can confirm that I found no evidence of structural damage attributable to the nearby site works. However, I did observe signs of damp within both the extension and the connecting hallway, as well as visible wear to the mastic and render on the external window reveals above the crack in the render that you highlighted.

In my professional opinion, the issues raised appear to be related to general wear and tear, possible water ingress at the junction between the original property and the newer extension, and typical shrinkage around plasterboard joints. These are common in properties of this type and age and are not indicative of any external impact from piling or site activity.

Given the nature of the issues, I would recommend contacting the contractor or builder responsible for the extension works. The areas in question appear to require routine maintenance and cosmetic repair, rather than structural intervention.

There is a small area of damp but this is nowhere near any of the cracks.  it is just above a skirting board in the original part of the house and in the extension on walls adjoining a shower room where parts of the grouting have failed.

Sorry for the length and would appreciate people's comments - obviously photos would help but I do not know how to do this.

many thanks

stuart45

You need an independent survey. 

Section62

melb said:

...
We then started to notice cracks inside and outside the extension and these have worsened in the last couple of years.  The cracks are at most about 2-3 mm wide so not horrendous but they are only on the side nearest to the construction site.
...

What kind of piling was it?  Some form of bank protection (e.g. sheet piles) or something structural (like bridge foundations)?

'30 to 40 yards' away ought to be enough that the risk of damage was minimal, assuming the extension foundations were adequate and the piling was for a relatively light duty purpose.

That the cracks have "worsened in the last couple of years" would suggest to me that there might be some other factor involved.  Structural damage from piling is probably more likely to hapen immediately (or at most very soon after) the piling operation takes place.  Worsening of the cracks over time might be assumed to imply ongoing movement of the ground, but with no obvious mechanism for the long-finished piling operation to be the cause.

Being at the 'top' of an old (how old?) quarry would potentially be a risk factor for movement, depending on what was being quarried and how long ago it stopped.  It might be plausible that some instability in the quarry excavation was re-energised by vibrations from the piling, and having started moving, the movement has continued despite the initiating activity coming to an end.

However, as stuart45 says, you need to get an independent report - ideally with some movement monitoring in the garden / at the quarry edge to see whether there is a movement over a wider area, or if it is limited to the extension itself.

Ectophile

We've had a lot of weather in the last few years.  That includes a wet summer last year, and a dry one this year.  Depending on your foundations and soil type, then that could be enough to cause movement.

Unless you get your own structural surveyor, you may never know.