What Affects House Extension Costs in West London

What drives the cost

The main parts of the design and site that can change a quote are:

• The size of the extension and whether it has one or more storeys.
• Ground conditions and the foundations needed.
• Structural steelwork and the work needed to open up existing walls.
• A flat roof or pitched roof, including its structure and finish.
• Glazing, including bi-fold doors and rooflights.
• The kitchen, bathroom and heating fit-out.
• Moving drainage, gas supplies and electrics.
• Site access and where materials can be stored safely.
• The standard of finishes chosen throughout.

Five costs homeowners often forget to budget for

• Design work and drawings.
• A structural engineer's calculations.
• Planning and building control fees.
• Party wall matters where they are relevant.
• Redecoration, flooring and landscaping after the main work.

Also think about whether you may need temporary living arrangements during the work.

Why quotes differ

Some quotes are itemised, while others give a single lump sum. Some use provisional allowances that can grow when the final choice or amount of work is known, while others are fixed. Specifications for windows, kitchens and finishes can also differ, even when the drawings look the same. Exclusions may vary too.

Compare quotes line by line. Check that each builder has allowed for the same work, materials and finish, and ask for anything unclear to be explained in writing.

We do not publish prices online because every property is different. We visit, measure up and send a free written quote.

R.A Developments offers a free site visit and an itemised written quote.