How Much Will My Extension Cost?

Before we start any building project we provide the customer with a detailed costed schedule. This is worked up by referring to detailed working drawings and by consulting at length with the customer. Often customers will not have decided exactly what they want so we will insert a provisional sum into our schedule which will be our best guess at the cost of what we think you are likely to want. This happens a lot when we are pricing extension that are being built to house kitchens or bathrooms. Often the customer wants a price for the building work before the kitchen or bath room has been chosen. Beware of quotes and estimates with low provisional costs. Putting low Provisions in, is a tactic used to keep your price below that of your competitors. Some contractors will not include any provisional sums at all which will keep their price low. So it is important to understand exactly what has been included in quotations when comparing them. Our priced schedules are laid out in a way that we hope makes this as easy as possible. Below is an example of a priced schedule. It has not been completed to save space. It is not unusual for these

So it is important to understand exactly what has been included in quotations when comparing them. Our priced schedules are laid out in a way that we hope makes this as easy as possible.

Below is an example of a priced schedule. It has not been completed to save space. It is not unusual for these schedules to run to 3 or 4 pages. The figures have been made up and are for illustration purposes only. We have continued with a list of headings to give you an idea of the level of detail we include in our prices. Putting time and effort in at this stage reduces the need for variations or “extras” to an absolute minimum.

Doughty Construction Quotation

Meterage rates and Budget Costs

Many people apply meterage rates to construction a popular one is that it costs £1000/m². This has been in use for as long as I can remember and many factors have pushed this figure higher. Slowly this figure has started to be adjusted by some people. I spoke to an architect recently who uses a figure of £1200/m².

So for a single storey extension that’s 4m x 6m = 24m² at the the architects figures 24 x 1200 = £28800

What about two stories?
Another rule of thumb is to add 50% for a first floor so:

For 4m x 3m two storey extension
28800 = 50% = £43200

What can effect this rule of thumb

Assess can be a large consideration, an example of this is, can large quantities of materials be dropped close to where operatives are working. Or does access allow for labour saving plant and machinery. If foundations need to be excavated by hand this could have a considerable effect on price. How far does spoil need to be barrowed before it can be removed? The list goes on.

Ground work is exceptionally difficult to price as you cannot see what you will be working with. We always recommend several trial holes, they cost money but if the ground is not what you expect you will be very glad that you have checked. Broadly we expect to find sound ground at about a meter if this is not the case it can affect the sort of foundations required.

Foundations can vary dramatically, on most domestic extensions the general assumption tends to be that strip or trench fill foundations will be used and that sound ground is found after one meter of excavation. Foundations will need to be deeper if building adjacent to a cellar. Trees can also affect the depth of foundations as can drains. Your extension may require a different sort of foundation, possibly a raft foundation or pilling. Your architect or structural will advise you on which you may need. The type of foundation required will have an effect on the cost of the work.

Level of Finish We have installed £4000 worth of lights in a bathroom. The bathroom could have been illuminated with a £15 IP44 light fitting. Clearly on domestic building projects the meterage rate will be substantially effected should the customer specify high cost fixtures fittings and finishes. Customers may or may not wish to consider compromises to manage building projects within a budget.

Scale of a project will make a difference to meterage rates. Smaller projects tend to have higher meterage rates due to economies of scale achieved on larger projects.

Hopefully you can see why even the most experienced estimator or quantity surveyor can get it wrong. When was the last time you heard of a large construction project coming in on time and on budget?
Wembley stadium?
The channel tunnel?

If only they had employed Doughty Construction!!

This highlights why it is important to get a quotation as opposed to an estimate and a good contract. How can you help the estimator work accurately? Plan your project think about exactly what you need, what you want and what would be nice. Consider what your budget may be.

What is Not Generally Included in meterage rates

Demolition of out buildings or part of the existing property may be required this would be considered an additional cost in these circumstances.

Professional and application fees, will vary from between 5 and 20% of the final cost of the project

Kitchens and Bathrooms can vary hugely in price and if you are building your extension to house a new bathroom or kitchen its cost will increase the meterage rate.

Steel work is not always the huge expense people think it will be, the insertion of small steels can be straight forward. However if you want to knock the corner out of your house, or want a four meter opening for bi fold doors, there will be cost implications.

VAT is something builders tend not to consider when talking about price. One of the reasons for this is that there are several VAT bandings that construction work falls under. New builds are zero rated, certain remodels fall under the 5% band. The bad news is that in all likely hood your extension will attract 20%. Beware builders who do not charge VAT. The VAT threshold as of April 2015 is £82,000 you do not need to do many extensions to hit that, and you want an experienced contractor.

So for a single storey extension that’s 4m x 6m = 24m²
24 x 1200 = £28800
Plus £5760
VAT £34560
Professional fees £3456
Total £38160

At the moment the cost of building is increasing faster than inflation. This is not because wages are increase dramatically or that companies are making more money. It is more as a result of the improving standards required by the building regulations. Among other things the thermal performance of new property has increased dramatically. Health and safety requirements have quite rightly been tighten up and are continually being tweaked. Also people’s expectations and standard of living tend to increase. More people want, underfloor heating, large bi fold doors etc.

At Doughty Construction we tend not to use meterage rates for anything other than budget costings. Even then we would consider among other things the level of finish required, what the extensions was to house, whether any demolition was required.