How to select a house extension builder
This is probably the most complicated and riskiest process a home owner will have
in getting their home extension scheme completed. Up until now, your home extension scheme has remained in the
virtual world of drawings, specifications and council approvals.
Getting the scheme from paper to physical completing on site is the role of your builder and everything will be
down to him to complete this process successfully irrespective of whether you are engaging your ‘building designer’
to monitor the works during construction.
Therefore due diligence is now more important than ever if you are to make the right choice of home extension
builder. It is not an exact science and even a good well respected builder can be wrong footed by a simple
personality clash with the home owner client. It can often be a situation of ‘horses for courses’.
Here we list some tests and actions you can take to reduce your risk of employing the wrong builder. It may not
be fully concise or a definitive check list but it will help reduce the odds.
1 - Use the recommendations of your Building Design Agent.
A well experienced building design agent who has handled & prepared your scheme through the various
regulatory authorities will have built up their own schedule of known and trusted builders for price and quality
over the years. Again, it will be a matter of fitting the scheme complexity, their clients attitude, size and cost
of the works to the builders on their list. Not all builders will be suitable for all clients or schemes.
2 - Use your own source of family and friends for recommendations.
Any successful business relies on word of mouth recommendations. Their last client is usually their next job.
Therefore, put the word around with your friends and family that you are seeking their advise on builders that they
have employed in the recent past. A successful and long term reliable builder will have built up a good source of
3 - Use your own previous builder contacts
Many home owners embarking on a new home extension have often had previous building works completed and are
possibly very satisfied with a known builder and are tempted to utilise the services of that same builder which is
great. Should this situation occur, it is vital that the ‘preferred builder’ does not know that he is the
homeowners preferred choice otherwise you may not obtain the best value price for the works. Therefore, you must
ensure that you still form the usual tender to at least 3 builders.
Another approach for when a home owner wants to have a preferred builder is to arrange for a negotiated price
contract but this is only really possible if the home owner has a point of reference for determining the new price.
This is usually applicable if the home owner has had some recent similar works completed by the preferred builder
where a base price can be established and the client is generally good with managing and assessing time, labour and
4 - Use builders that belong to professional bodies
There are a number of professional institutions that builders can join or be members of and most have a code of
conduct. However, it must be remembered that they are a trade or profession organisations paid for by the builders
themselves so it is not exactly independent for you the consumer but that can be said of any professional body
really. They are nearly all paid for by their members.
This does give you some form of redress or formal avenue for complaint should things go wrong but most do not
offer an automatic financial recovery option for non-performance of failure of duty by the builder unless you have
pre-paid some form of insurance cover - and we all know how they can wriggle out of paying out monies when
However, if the Builder is genuine then he does run the risk of being bared from the professional institution
that may be a very important marketing tool or status image for him so it does have some use for you in the long
5 - Use of cold calling unknown builders from advertisements (the yellow pages lottery).
This really is the last resort and is riddled with possible problems. If you do go down this route then you must
complete a lot of additional due diligence checks over and above the normal regime. Check out previous clients (at
least 3 per builder), research their previous financial & company history, check their professional
institutions that they are indeed full members and ask the local Council Building Inspector for an opinion on who
you would like to engage.
6 - Golden rules and checks you should do before engaging your builder.
6.1 - Check out previous recent clients. Go see their work and speak to the builders previous clients. Ask about
cleanliness, quality of workmanship, reliability & contract period. Dig a little under the overall gloss. Its
amazing what issues & stories often lurk beneath the surface.
6.2 - Obtain copies of the builders insurances before you start on site. Most will have the usual 3 to 5 million
third party cover which does NOT cover you for errors or omissions by the builder. It simply covers third parties -
that’s it. Some builders pay for additional cover or have an all risks policy but this is expensive.
6.3 - Check out their professional bodies that they are in fact full members as stated.
6.4 - Obtain financial health checks on their finances & previous companies.
6.5 - Obtain their mission statement and ethics on employing trades.
6.6 - Agree payment terms - money paid for work completed only either at set agreed stages or at due timed
periods. Do not provide up front deposits & do not pay more per draw than what has been completed on site.
6.7 - Hold back a small retention on all payments. 5% is normal with 2.5% released upon practical completion.
Final 2.5% released 6 months later upon satisfactory making good of any defects. This needs to be part of your
6.8 - Agree to the formal contract to be used. There are many external building contracts
for small to medium sized works. The Federation of Master Builders (FMB) have a really good plain English contract
that is worth looking at rather than the more confusing JCT ones. Many builders for home extension schemes are
simply engaged on an exchange of letters between the builder & client referring to the Design Agents documents
but this is only relevant for when the home owner has engaged a professional building design agent right from the
start and they have prepared a good specification in association with the usual drawings.
6.9 - Agree a contract period for the works. There is machinery for enforcing the end date by using penalty
clauses or liquidated damages but this can be complicated & deemed an unfair contract if not done correctly and
often best avoided for smaller works. Expect delays due to the builder being let down by the weather and his
trades. A 12 week contract period will often end up 4 weeks late.
6.10 - Agree working hours, working days, material storage areas, parking, access, methods of scheduling,
agreeing and costing variations, locations of toilets etc.
6.11 - Check their VAT reference number is correct & that they are indeed registered for VAT.
NOTE: Assuming that you had previously engaged a professional building design agent for the preparation
of your plans & specifications for the construction scheme, you may find that all this is already included
within your design Agents documents. If you engage your Building Design Agent to handle the Contract Administration
during the works then this will form part of his duties.