What causes

Cracking around  bay windows?

There are several reasons that cracking around bay windows occurs, and this is often due to their original construction.

Bay windows were very popular in Georgian, Edwardian and Victorian houses, and building of the bay was often left until late on in the construction process so that the opening could be used for access.

Georgian properties tended to be built to a high standard with good quality materials, on foundations dug down to solid ground. However, Victorian properties were built faster, with cheaper materials, and the foundations were not always dug deep enough. Because the bay was often built late on, they were sometimes built on separate and less adequate foundations to the rest of the building and were not adequately tied in. This can lead to differential movement where the bay moves, but the rest of the building doesn’t.

This is particularly a problem in areas such as London, where the properties were built on clay soil. Clay soils are more vulnerable to subsidence because the soil shrinks when it is dry. Heave is also a problem because clay soils expand when they are wet.

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Vertical crack where bay window has detached from main structure
Bay window repair almost complete

Other factors

And what to look out for

Other factors affecting the soil can include:

  • Poor, blocked, or leaking drainage
  • Trees that are planted close to the property sucking up moisture during dry spells
  • The removal of trees and other vegetation

Warning signs to look out for include:

  • Vertical cracks in the external brickwork between the bay and the main structure
  • Internal cracks in plasterwork or distorted wallpaper
  • Windows sticking
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Method of

Bay window repair

Twin bands of helical bar are bonded into predetermined slots cut into the bed joints around the bay above and below the window, with the ends embedded in the front elevation. Lateral Restraint ‘Bow Ties’ are then driven into the joist ends via pilot holes in the masonry and low-level cracks are stitched with single helical bar crack stitches.

Colour-matched pointing mortar is then used to match with the existing mortar to provide as near an invisible repair as possible.

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Diagram showing bay window repair detail
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The Helifix method of

Bay Window Repair

How to Repair Bay Windows | Helifix UK

Call us for help with any of these

Common structural defects, issues and problems

Crack Repairs
Bay Window Repair
Concrete Repair
Micro Piles

Cavity Wall Tie Replacement
Movement Joints
Bridge Repairs & Maintenance
Conventional Piles

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To trust ASRS

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Free Quotation

We offer free site visits to both domestic and professional clients to assess the problem and propose the appropriate repair programme, tailored to suit the specific needs of the project.

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Helifix Approved

ASRS are approved installers of the Helibeam System, offering cost effective, non-disruptive and concealed solutions to all aspects of remedial masonry stabilisation.

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Skilled Workforce

Our skilled installation teams are trained and experienced in all aspects of masonry repair. They have been trained to the highest standard in every installation process to cover all H+S requirements.

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With most of our design and installation specifications we are proud to offer a 10yr indemnified guarantee on Helifix repairs and Micro Piling. We offer a 25yr guarantee for Wall Tie replacement.