stress cracks on glass in norfolk

11th May 2022

Five Reasons Why Windows Crack and Break

Let’s talk about broken windows… we’ve all been there from a tiny crack to a full on star break, whether that’s from accidentally kicking a ball too hard or due to bad weather. Here’s five reasons why windows crack and break.  

Stress cracks

One of the most common cracks in a window is stress cracks. Mainly caused by drastic changes in temperature, they usually start small near the edge of the window and then spread across the glass. If one part of the window is shaded and cold and the sun is directly shining on another part, this causes it to expand or shrink resulting in stress cracks. The bad news is these cracks can’t be 100% prevented but when replacing your windows it’s advisable to opt for glass features that suit the climate, such as thicker double-glazed glass to decrease the risk of cracks occurring again. Stress cracks can also form due to slamming the window shut too hard – so be gentle folks. 

Impact break

Ever had a football, tennis ball or even a golf ball smash through your window? This is an all too common problem many homeowners and even commercial property owners experience. As soon as you see the starburst pattern radiating outwards you know a full glass replacement is on the cards. When this happens, it’s important to clear up the loose shards of glass but do not attempt to remove the remaining broken glass left in the window frame by yourself. Wait for an emergency glazier to assess the damage and fix accordingly. 

Pressure cracks

A less common crack but no less important to sort out. Pressure cracks are usually seen in insulated glass or double-paned windows and caused by changes in pressure due to extreme weather or incorrect window installation. If there’s not enough room left around the window to allow for expansion and contraction, windows can become tight putting pressure on the glass which forms a curved crack in the shape of an hourglass. 

Bad weather – storms 

Storms are never good news for windows; tree branches, hail and general debris can cause some serious damage. It’s always a good idea to document the damage by taking some photos to submit along with your insurance claim. Then it’s up to an emergency glazier to assess the situation and, depending on the severity, advise whether the glass needs to be completely replaced or can be repaired. Storm damage is usually unavoidable by trimming nearby trees can reduce the risk in preparation for when the next storm brews.  


Something you hope to never experience, but unfortunately vandalism can occur on both commercial and domestic properties. In the event of such an incident your first point of call should be the police then an emergency glazier to secure the property. An assessment of the damage will be carried out and if the glass needs fully replacing or is made to order it will need boarding up in the interim. If any locks have been damaged, our sister company City Locks are also on hand 24/7 for emergency repairs and replacements. 

At Norwich Glass we understand the importance of sorting out window breakages quickly and carefully which is why we offer an emergency 24/7 glazier service. Cracks, whether big or small, will only get worse so don’t wait to sort them out. Our team is always on-hand for all your glazing needs, call us on 01603 431409 or email

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