Bay Window movement, 1930's house.

Phil4432

Evening all,

This really has been a source of worry for me, so any help would be much appreciated.
First off all, I know that 30's Bay Windows are just going to move at some point. We are on clay.

What I'm really, really keen to avoid is underpinning, which could devalue the house.
This house was bought in late '14, and the survey at the time highlighted a fine crack to the Bay Window. The report said that differential settlement could occur over a period of years due to its construction. The crack was plastered/painted so no ingress nor damp. It corresponded to an internal crack in the upstairs bay window, which has changed little in the last 7 years.

However I recently noticed at the start of September, that the crack had opened to around .5mm. Looking at it today, its expanded to 1mm. I put a 6cm strip of paper in the crack, it went in all the way.

I know .5mm expansion in 2.5 months isn't loads and we've had a very dry summer. But clearly something has changed, as this wasn't happening in the previous 7 years we've been here.

Any thoughts on this really appreciated.

Update, a surveyor said its not much to worry about and most probably signifies movement following the dry summer and then rain, as opposed to subsidence.

He recommended looking into the Helifix method to remedy. 

Bigphil1474

We had subsidence on our bay a few years ago. Ours was a sudden movement caused by a leaking drain.

Not sure what the pictures are supposed to show, but was commenting as our insurance company had to monitor the movement for about a year before doing any repairs. To monitor, put a mark either side of the crack, say 100mm apart. Measure the gap every week, and see if there's any change. If it's not moving, it could just be the fix that needs redoing. Others may know more.