Subsidence without external cracks?

20 Dec 2016
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United Kingdom

I recently bought a house. After moving here, it was discovered there was tree root damage to the drains which I had fixed.

There were quite a few internal hairline cracks so before buying it I got a building survey done which found no evidence of movement.

However, since discovering the problem with the drains I am concerned the surveyor may have missed the significance of the cracks.

There are no external cracks. Is it possible to have subsidence without any external cracks being visible?
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If the internal cracks were present for the mortgage survey then what did the surveyor say about them - if anything?
Most houses have cracks and most cracks are insignificant - from the limited information you post I should imagine that your cracks are not significant.
dijc, Good evening.

OK so there was some root penetration of the drains, how far from the property was this intrusion located? Did the drains back up? was there a CCTV survey undertaken? and more importantly were there any cracks or displaced joints found, and repaired?

In general terms, a leaky drain can occasion Subsidence but [there is generally a but?] a lot of factors involved such as soil conditions, distance of drain defect from the property, severity of the drain damage Etc. Etc. Etc.

As for hairline cracking, occurs all over the place, plasterboard cracking? skim coat of plaster cracking?

Turning to internal wall plaster cracks but no external wall cracks? in the face of previous posts, yes it can occur but [there is generally a BUT?] the last one I surveyed was a Glasgow Tenement ground floor flat, where for many years the internally sited communal waste stack had leaked, this in turn massively softened the ground below the internal main load bearing wall founds to the extent that there was a localised Subsidence event affecting the two main internal load bearing walls. there was no damage to the external walls, and no damage to the other walls just 2M distant from the main event?

Bottom line, a drain defect has to be in close proximity to the damage, and the leak has had to be on-going for a long period of time, combined with ground conditions and ground types. after all Sand will react differently to say a loamy soil, or clay?

As an aside from the information you have provided, you do not appear to have a Subsidence event on your hands.

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Drains with roots in don't tend to leak very much unless they block up. If they do block the water can escape further up from open joints or more often from between a gully pot and its hopper.

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