No. 1 | No surprises.
How much does a house extension cost in Bath 2024?
How can you help manage the costs involved with my project?
One of the first conversations your architect should have with you, usually the first time you meet at the initial consultation, is about your budget. They should ask what you want to invest in the project and discuss this in relation to your brief, or what you want to achieve.
Sometimes you might not have a fixed figure, but there will usually be a number which causes a sharp intake of breath, and you may have a ceiling of the property value to consider.
We provide project cost plans for all projects, and can work with a figure you already have in mind, or provide options based on square meter rates.
When detailed cost information is required prior to builder’s pricing (tender), we work with a quantity surveyor who is trained in pricing construction and has access to industry data.
Why have build costs gone up?
Building costs have risen dramatically over the last few years, initially caused by shortages during the pandemic, and then exacerbated by inflation.
But even after the effects of the pandemic subsided other economic factors have kept prices high and it’s doubtful that prices will revert to previous levels:
1.The Russia-Ukraine conflict has resulted in severe shortages of materials and fuel.
2. Brexit has contributed to shipping delays, decreased availability of foreign workers, and a widening gap between exports and imports (trade deficit).
3. Persistent high demand allows builders and suppliers to command higher prices.
How much should I budget for VAT and fees?
In addition to the construction cost, your budget will also usually need to cover:
Design fees (architect, structural engineer, interior designer, garden designer)
Measured surveys
Drainage surveys
Local authority planning approval fee
Building control approval fee
Other consultancy fees (e.g. party wall surveyor, planning consultant, historic building specialist, ecologist, mechanical and electrical engineer)
Contingency (especially important on work to existing homes)
VAT on all of the above
Client supply items (things traditionally not supplied by the builder, for example special light fittings, tiles, floor finishes, kitchens, sanitary wear).
When estimating high level budgets, we assume these items will account for approximately 30% of your budget, with 70% remaining for the net build cost.
We break down each project individually as part of our services.
House Extension Budget
How much does an extension cost per square metre?
Because an extension is usually modest in scale, many assume that this type of project will be low in cost. However, there are fewer economies of scale in smaller projects, therefore the cost per square metre is comparatively high.
Building in Bath is similar in cost to London, as unfortunately we do not have the advantage of labour availability of the capital.
The following building costs per square meter are based on data from Build Partner for 2024, and are based on a mid-spec or standard finish.
Cost of building a ground floor rear extension (by region)
Low benchmark | Smaller builders are generally lower cost but less specialised and with low project management function; good for low/mid-spec projects and tight budgets.
Mid benchmark | Medium-sized builders offer a balanced mix of cost-effectiveness and specialisation, good for mid-range projects for effective execution within moderate budgets.
High benchmark | Larger builders generally have a higher cost base but can handle a wide variety of specialist tasks; good for mid/high-spec projects and project management.
Cost of building a Ground-Floor Rear extension (By Region)
Average Cost Per Sq Metre (excl. VAT)
South West
low £2,559, mid £2,792, high £3,064
London
low £2,897, mid £3,269, high £3,607
So what budget do I need to allow for?
A typical rear extension in Bath is
20 square meters
so this equates to a total build cost range (excluding VAT) of £56,000 and £64,000, averaged at £60,000.
An extension project rarely stands in isolation though; an additional cost will apply for works to the adjoining room which is often the kitchen. This will likely require fitting new kitchen units and appliances, along with a reasonably intensive refurbishment, we may estimate a rate of £2,500 per square metre for the existing room. Assuming a size of 20 square meters, this results in an additional £50,000. So, in total, this gives an estimate build cost before VAT and fees of
£110,000
+ VAT and project costs
With the build cost making up approximately 70% of the total, we would estimate this project requires an overall budget of:
£160,000
Where should you make savings on your project?
Find out which corners you can cut to make savings in our next post. Go there now.