How much is my extension/refurbishment/new build going to cost?

When it comes to building costs and professional fees one of the most frustrating things for Clients is that they find it difficult to get a clear answer.  How much will my building cost? The answer is unfortunately: it depends! For example are you thinking to go for a high specification or a low one?  What area of the UK do you live in?  Do you want your Architect to look after the project up to completion on site or would you rather risk higher costs and go to a Contractor after obtaining Planning permission? Will you change you mind during construction? These are only some of the issues that may affect how much your extension/refurbishment/new build is going to cost.

Estimating Building Costs (Please note that these figures are indicative and they are not intended to be anything more than a helpful guide).

It is very difficult to give an accurate cost per sqm of the building expense as there is no exact average to go by as every site is different: drainage positioning, access to site, site conditions, etc. But assuming that we have ‘normal conditions’ and assuming that the specification is ‘standard’ and that you do not make any changes during construction (which would immediately increase the cost and time of the project):

1)      Standard construction, no significant structural issues, standard specification

£1,500.00 per sqm

2)      Higher specification some structural or site related complexity

£1,700.00 per sqm

The two main problems in identifying building costs are that contractors can quote very differently from each other and the other problem is unexpected surprises during construction (i.e. an old drainage chamber or extra structure is discovered to be required only once the walls have been demolished etc.), which hopefully can be covered by the presence of a 10% contingency fund.

Your Architect can help you get a more accurate building cost:  if you employ your Architect to prepare a specification, a Scope of Works and detailed drawings your costs will be kept under control.

What is a Building Specification? Let’s say you have obtained Planning Permission and Building Control clearance for a small bathroom extension, the next step would be for us to prepare a Specification.  In a Specification we will help you make decision regarding for example the kind of wall tiles you want to use, or the kind of bathroom fittings you want and compile this in a document which will also give instructions as to regards the supplier you want to use and the way you want things done (example: you require a ceramic bead at every corner to give a higher standard of finishes!).  This will give the Contractor clear instructions as to what materials you want to use, and will enable him to price things more accurately and ensure you get exactly what you like (not some cheap tiles from the contractor’s best friend!).

What is a Scope of Works? In this document we will give a general description of the works, allowing the contractor to familiarize with the works before he gets stuck in the complexity of the specification.  We usually do the room by room on a big project and do an entry for floors, ceiling and wall treatment/demolition etc.  We also give an indication to what kind of electrical and mechanical system is to be used.  This is an important document and will again be used by the contractor to give a more accurate estimation of costs.

What is a detail design? Detail designs are important because they show the contractor how we want the construction of the building to look like.  So for example a detail of a flat roof will show the contractor what materials he is supposed to use.  For example, often bad Contractors, like to use cheap insulation that are inflammable and not made by natural materials becasue they know that the Client ‘would not know better’ without the guidance of an Architect!

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Once the Contractor has read the documents and looked at the detail design he will give a price for the works.  We will ensure that we get at least five contractor to price for the works and help you to make a decision as to which contractor to use and also ensure that he sticks to the price he has given by putting it in writing in a Contract.

Remember that an extension can add around 25% to the value of your property!