Garage subsiding?

[Scratchface]

I have recently noticed cracks in the brickwork of my detached garage. They weren't there last summer when I replaced a couple of windows.
We live on the border of chalk and clay. Garage was well built with piers etc. in C1980s.
Work started on a housing development behind our garden this spring. In May a large concrete slab was laid 4m from the garage, the Council said it was for a container.

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• Scratchface
• 11 Aug 2014
• 1

Between the garage and the concrete slab is a hedgerow I planted 18 years ago comprising hazel, hawthorn and beech.
A surveyor friend has suggested monitoring the situation by taking photos which I have.
The biggest crack is about 20mm wide to the left of the door shown in the photo.

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• Scratchface
• 11 Aug 2014
• 1

The rear corner of the garage is 1.5m left of the door.

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• Scratchface
• 11 Aug 2014
• 1

Lintel is above the door and a window I replaced last summer.

I have left the hazel,hawthorn and beech trees grow to about 20ft to give a bit of privacy as new houses are being built just a couple of metres inside the boundary.

What are my options?
Thanks in advance.
Jim

 

[theprinceofdarkness]

I would say that the tree roots are sucking up water out of the clay, which is then shrinking. Also the roots go out a long way from the trees (there are tables for this), but a working distance would be their height.
The weight of the garage is going downwards, so unless some one has removed a lot of soil depth near to the garage it would not have any effect.
Frank

 

[Scratchface]

Thanks Frank,

As shown by the picture of the slab quite a depth of soil was excavated followed by a lot of vibration to compact the hardcore base.

Jim