How Much Will It Cost? 

Regardless of the size of the job, it is worth bearing in mind: 
 
Builders will price jobs in different ways. When comparing costs, make sure you know what has been included so that you can make a fair comparison. 
 
The more detailed you can be about what you want, the more accurate a price your builder can give. A builder can put a ballpark figure on initial ideas, but a more detailed brief and architect’s scaled drawings help the builder understand what you are hoping to achieve. 
 
Ask your builder what they have included in their quote. Some may price just the basics while others will provide more realistic total costs. 
 
A fixed price isn’t always the best price. It is relatively easy to work out a fixed cost for the fabric of an extension but internal alterations, intricate flooring or a bespoke kitchen can be harder to cost. Drainage or foundations can be complicated by unforeseen issues. In preparing a fixed price, a builder may overestimate the cost to cover any risk. Alternatively, ask for budget figures on certain items that can be reviewed as the work progresses. 
 
Don’t choose a contractor purely based on price. Trust and professionalism are priceless! 
 
It is very difficult to put a standard price on any building work. Which? magazine (January 2021) suggests a small single storey extension can cost upwards of £30k whilst a 2 storey extension would start at £75k but location, scale, complexity and specification all affect the cost e.g. a kitchen extension will cost more than an office or playroom. 
 
As well as any structural costs, you should check whether your builder has included: 
Upgrading electrics or heating system if necessary 
Kitchen/bathroom fittings 
Landscaping/external works 
Flooring and decoration 
VAT 
 
In addition to build costs, you will need to consider: 
Architect/designer fees 
Structural engineer fees 
Planning permission costs 
Building control fees 
Contingency to cover any works to attend to unforeseen issues. (10% is usually recommended) 
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