Spot the defect – bay windows

Bay windows are popular features in new homes and add considerable aesthetic appeal both inside and out. Yet constructing bay windows is a task that should not be taken lightly, putting extra demand on detailing and workmanship which can prove problematic to correct later on.

The image below shows the head of a full height PVCu bay window. Can you spot what’s wrong here?

Spot the defect - bay windows

Did you identify the problems here?

Instead of the window frame overlapping the vertical DPC present in the reveal, it is installed against the outer feature stone leaf (see the orange arrow in the image below), creating both a cold bridge and a path for moisture to reach the internal finishes where gaps in the damp proof course occur.

While a vertical DPC wrap has been incorporated over the exposed section of the outer leaf in an attempt to overcome lateral damp penetration, some of the outer leaf is still visible and no precautions are apparent to deal with the cold bridge.

Spot the defect - Bay windows 2

With an arrangement such as this, the plasterboard’s adhesive dab will be placed onto the DPC, which is an inappropriate substrate offering insufficient support to plasterboard.

This blog can help you spot – and avoid – some of the more common defects to bay windows.


Please Note: Every care was taken to ensure the information in this article was correct at the time of publication. Any written guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. However, for the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty technical manual.


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