January 20, 2023

How much does a side infill extension cost?

Written by Rebecca Clayton

A cost guide to side infill extensions

Side infill (or side return) extensions are a great way to open up unused spaces and utilise natural light. Side infill extensions are typically seen in Victorian and period terraced properties where extending to the redundant alleyway at the side creates more useable living space without encroaching on the rear garden. 

A glass side infill extension can seem costly, however, the common alternative is dark, unused storage areas or completely wasted space. But how much might an addition like this cost?

The starting price for a glass extension of this nature would be approximately £10,000 for a simple glazed link, or for a small glazed area. When considering costs, do bear in mind that due to the bespoke nature of glass structures, it is not simple to provide generic estimated costs for glass structures.  Firstly, updates to Building Regulations in line with the government standards to ensure best thermal performance can push the costs.  Secondly, the cost of raw materials can fluctuate during economic and political volatility.  Lastly, factors such as the design, size, shape of the glazing panels, location etc. can all have an impact on overall costs.

It is increasingly popular to incorporate a window or door into the glass structure to open up living spaces and improve access to the rear of the property, particularly those with a garden. Adding a window or door may also allow the property to benefit from the maximum natural light throughout, bridging the gap between indoor and outdoor living. The cost of incorporating a window or door into the structure would vary dependant on models and sizes desired, as a cost guide, the glass for this would take the price closer to £15,000.

Chandos refurbishment wanted to increase the height for maximum light into the new kitchen diner space.  This sidefill extension included casement windows and doors with structural up and over roof glazing. The cost of this project in 2020 was just under £20,000.

As far as planning permission goes, providing it’s a considered extension at the rear or side of a property, your glass extension shouldn’t require anything different than a regular extension would.

For further information on glass sidefill extensions please contact the team at email: hello@iqglassuk.com.