3 Westgate Street, Southery.

PE38 0PA. United Kingdom.

studio@anthony-johnson-engineering.co.uk:

Telephone

01945 660504

An Engineering Practice:

Based in the Heart of the Fens, North of Cambridge, Anthony-Johnson offers Structural, Geotechnical, Civil and Environmental Engineering services to Homeowners, Architects, Builders and Businesses in Wisbech, Kings Lynn, Downham Market, Thetford and surrounding areas

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Buyers Survey

Last week, I was asked to carry out yet another Structural survey. Having completed the survey, I didn’t think it was worth repeating myself and putting anything up on the examples page. There were a few cracks to the property which certainly weren’t of concern.

One of the cracks, top the underside of a window followed a plane of weakness in the brickwork, where builders had inadvertently lined up bed joints vertically. The same crack appeared around brickwork to the top of the window.

However (and this is a big however), whilst visiting an event in Whittlesea, I happened upon a long freestanding wall (about 30 meters long) which had a vertical crack that had propagated the entire height of the wall.

That got me thinking- Had the addition of a new UPVC window on a South Westerly facing wall inadvertently introduced a plane of weakness in the wall itself, allowing a restraint crack to develop? This form of cracking is typical in a wall 30 meters in length but not very common in a detached bungalow.

It’s the reason why Building regulations specify the need for vertical movement joints in long walls- to allow for expansion and contraction due to changes in temperature!. However, the size of the opening for the window and the changing of the window frame to UPVC as opposed to timber could have caused restraint in the wall so that as it expanded and contracted, the weakest point in the wall failed. The issue with that hypothesis was that the crack was nearly 800mm from the edge of the window frame. However, it did happen to coincide with an internal partition that was in turn restrained by the chimney breast and a line of weakness in the brickwork itself.

Either way, the vertical alignment of mortar joints (see image right) clearly points to a vertical plane of weakness in the masonry. As can be seen in the image, a bed joint, one course down from the window cill is poorly pointed and this line of mortar has cracked and spalled. The crack runs horizontally right under the entire window and then down the wall. Thankfully in this instance, it’s clear from the brickwork below the Damp Proof Course (the bottom course is Engineering Bricks with DPC over) that there hasn’t been any movement in the foundations, meaning that this can be easily rectified with little extra cost.