Extensions. How to calculate build cost.

5 points to consider to determine how to calculate build cost.

Its worth spending a bit of time to carefully consider the fine details of your project and what you want to achieve. Getting your estimates wrong can be a disaster for your project and lead to falling out with your builder. follow these 5 principles and you should arrive on budget or close to it.

  1. Decide on your level of involvement.

Are you going to be doing certain works yourself and using sub-contractors for the rest? do you want to project manage the build but sub-contractors do the works? You can contract a builder and have subcontractors. Or you can hire a Main contractor to do all the works.

2. Determine  the size and shape of the extension.

Build cost increases when you build non standard construction methods. The cheapest construction will be a standard rectangular shape with rectangular windows. If you incorporate curves and non standard windows, like quarter arch, half arch, eyebrow windows, or frameless glass sliding doors, then prices rise.

3. Write down your budget.

With every build budget, you must add a contingency budget. Unfortunately more often than not, problems arise during a build which you hadn’t foreseen. This is not down to a lack of planning, but issues arising from having to relocate pipes or cables only discovered while digging footings, which may not have been accurately portrayed on any land registry documents. Maybe your boiler cannot handle the loading of extra radiators or under floor heating, so needs to be upgraded. Or, groundwater is higher than expected and new soak-away’s have to be built.

4. Be clear on the standard of finish you want.

Builders generally quote for ‘Standard finish’. You can opt for a ‘good’ finish or an ‘Excellent’ finish. As you know, You pay extra for quality. look at these examples of standard, good and excellent internal doors and see how one product affects price.


5. Getting Quotes from tradesmen

we at https://propertyspacesolutions.co.uk work in the south east around Buckinghamshire, Berkshire and Middlesex areas, so I will give you the guide price build costs for this area. So when you contact builders you will have a rough idea of what to expect.

If you want a Main contractor builder.

  Expect to receive quotes around £1600sqm for a standard finish build. £1800sqm for a good finish build and around £2000sqm for excellent finish build

The benefit of hiring a main contractor is, he is responsible for everything, he cannot levy blame on another tradesman. Therefore from a legal stand point its straight forward for you. He is also responsible for the timing of any sub-contractors arriving on site to do works in a schedule that doesn’t hinder other workers from doing their job. An example of this would be; The electrician needs to lay cable and finish before the carpenters fit the plasterboard. A delay of a day or two can mean carpenters or plasters are no longer available, as they will have scheduled in this work weeks in advance.

Builder and Subcontractors.

standard finish will be around £1400sqm Good finish £1600sqm and excellent finish around £1800sqm.

All sub-contractors and you project manage.

Standard finish will be around £1300sqm. Good finish around £1500sqm and excellent finish being around £1700sqm

DIY and sub-contractors.

Prices will be around £1200sqm for standard finish. £1300sqm for a good finish and £1600sqm for an ‘excellent finish’.

If you decide to be involved with project managing, this can involve ordering the materials or simply paying for the materials to be on site. the key challenge will be getting all the different contractors to complete their works within a specified time. To do this, you need a time contingency. This contingency needs to be factored into the outdoor trades like foundation works and bricklaying. These are weather dependant trades so factor in wet days or allowing for frost if doing a winter build.

Be sure to order your windows well in advance as many trades cannot start until the building is weather proof.

We at property space solutions Ltd offer a full build service. We hope we can assist you. Please contact us gary@propertyspacesolutions.co.uk for advice and an estimate.




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