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dos and donts for building a home extension marlow bucksDo's and Don'ts of the home extension build process on site with your builder - A clients guide to building a home extension


This guide assumes that you have now obtained or, about to obtain, an official contract start date in writing form your builder together with a mutually agreed payment schedule. It is assumed that you have completed your due diligence checks before engaging the builder.

You must also advise all the other builders who were unsuccessful in their tender - Please do not ignore them - They would appreciate being informed.

This guide assumes that CHP will not be engaged for the ‘Contract Administration’.


  • Do monitor the works & assess the work progress against the contract period. If you feel it is slipping through fault of the builder inform him immediately & back it up in writing if necessary. Record any explanation given.
  • Do check that the Building Inspector is monitoring the works at the required stages. Double check with the Inspector at his offices if there is any doubt.
  • Do obtain in writing any deviations or variation of works from the agreed drawings or Specification manual. Obtain costs (add or omit prices) for every variation BEFORE allowing the deviated works to proceed. If the builder wont do it - YOU MUST DO IT & get him to sign your letter/variation schedule.
  • Do schedule any days of missed work including those that are attributed to adverse weather conditions & those which were not.
  • Do Pay the second Building Regulations Inspection fee when required. The council will be sending you their invoice direct.
  • Do obtain the completion Certificate from the Council prior to issuing the final payment to your builder.
  • Do be patient with your builders contract trades. It is getting harder & harder to obtain decent trades that can perform on time. Many builders are at their ransom & a trade ‘walk-off’ the job half way through can be disastrous. Always give the benefit of the doubt first & any pressure required for the trades to perform must be sought through the builder - DO NOT APPROACH THE TRADES PERSON DIRECT - you do not have a contract with them - your builder does.
  • Do ensure that your builder is not installing works over the agreed boundary line with your neighbour.
  • Do always pay your builder direct the interim monies due as per your agreement & only in the form of a cheque. Do not pay in cash. Always obtain a receipt which is normally a signed copy of his invoice & should include any variation costs (add or omits) attributed. Do not leave the variations to be accumulated & settled at the end of the contract.
  • Do make sure that your builder is working in a safe & tidy environment. A messy site with clutter is a dangerous site. Also make sure that you are attending to the needs of your neighbour & keep them informed (e.g. access for scaffold). Having a good & attentive bedside manner with your neighbour will keep them sweet & stop any pent up feelings they may have getting out of control. You will also retain good neighbour relations at the end of the job. Thank them also with a crate of quality wine & appropriate ‘thank you’ card as soon as the builders have left.


  • Do not change the works on site or alter the specification during construction unless it is really unavoidable. It will be expensive in the form of abortive costs & extras.
  • Do not pay any monies up front or in advance of the works. Any expensive materials delivered to site awaiting installation (e.g. - new boiler) is reasonable to pay for PROVIDED you obtain a written receipt, the item has been stored correctly & safely & are fit for the purpose. If they get stolen prior to installation it is your responsibility.
  • Do not discuss any inferior workmanship issues or worries with the trades direct - Always go through your builder or main contractor first.
  • Do not be afraid to challenge your builder on any of his requests to alter the specified materials for example. Enquire to his reasoning. His motivation to do so is normally a cost or time saving rather than delays in obtaining the specified material. If there is a cost saving then ensure you advise him to provide you with a credit if you agree to the change.
  • Do not accept continuing excuses from your builder. After the initial benefit of the doubt has been given on your part explain quite clearly what you are expecting from him & what he is contracted to do. Obtain commitments from him to rectify any problems & YOU must then confirm them in writing to him requesting his signature on one of the copies.
  • Do not be afraid to contact CHP if you are under doubt or worries with regard to the contract or works on site. CHP can normally condone or endorse any builders action or inaction over the telephone once you have explained the situation.
  • Do not release all the money for the interim payments. It is quite acceptable to retain 5% retention. 2.5% is then released upon final completion & the remaining 2.5% released 6 months later after satisfactory completion of any snagging items (if any) that you may have encountered. This is fairly standard practice irrespective of what the builder may tell you. This area of payment terms should have already been discussed & agreed before engaging your builder.
  • Do not be tempted to be vindictive with any payments held on retention. All builders will experience problems - it is their honesty & commitment to overcome such problems you should be judging. If they are entitled to it - release it.
  • Do not be belligerent with your builder any on site problems encountered. This often just entrenches peoples opinions & actions. Try to take a pragmatic approach for each scenario that may arise. A successful build often entails all parties pulling together which often requires a bit of ‘give & take’ to ensure the project continues & remains on track. Any doubt on this issue contact CHP for his opinion.

I hope this short guide of the building period is of use to you & has answered your questions that you may have had. It may not be fully conclusive in content & is merely a memory jogger of some items. If it does not answer all of your questions, please do telephone my office & I will try to assist further. 


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