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The Ultimate Guide to Home Completion Certificates

As you build your new home, certain aspects of its construction and performance need to be approved by different building industry professionals, such as structural warranty providers, registered electricians and commissioning engineers.

Organising these certificates and the paper work that goes with them gathers pace as the completion date nears, but don’t get so caught up in last-minute construction details that you fail to obtain these approvals: your local building control will not issue a completion certificate until you have them all.

Structural Warranty

If you obtained a 10-year structural warranty scheme to secure a mortgage for your self-build project, the policy issuer will provide a completion certificate after the final inspections are done. This building defects insurance document (also called latent defects insurance), along with the Building Control Completion Certificate, needs to be kept in a secure location, as you can use it to claim a VAT rebate.

Electrical safety

When your home is hooked up to the power grid and the first and second fix have been completed, you will need a final certificate from an electrician registered under the Part P scheme. They will test the circuits and produce the certificate if the results are satisfactory.

Air pressure

During the planning or early stages of your build energy efficiency calculations will have been worked out including an air tightness value. A result lower than 15 will need to be verified after completion by a member of the Air Tightness Testing and Measurement Association, who will carry out the test and certify the result.

During the test, a portable seal will be placed over your new home’s front door and air from a large fan will be sent into the house to create a pressure of 50 Pa (pascals). The reduction of air pressure via leakage is timed to work out the actual air tightness value.

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The home’s designer should of already assigned an air leakage rate using DER calculations. If the test shows a higher result, the insulation will have to be improved to make the higher rate acceptable, or gaps will have to be sealed to improve the air tightness.

SAP rating

A Standard Assessment Procedure, known as a SAP rating, will have been worked out during the design of your new build property. SAP is designed to provide a rating of the overall energy efficiency of a building. It takes into account a number of factors including space, water heating, ventilation and lighting.

This calculation must be verified on the finished building before a final certificate can be produced. If any changes were made to the home specification after the initial test was done, the SAP calculation should be redone to ensure an accurate target figure.

Fuel storage

Self-builders in rural locations often used stored gas or oil, requiring a certificate from a recognized authority, such as OFTEC for oil and CORGI for gas.

Chimney and open flue certificates

If the home has a working fireplace and chimney, it will require testing. A core ball test will verify that the flues are not blocked, and a smoke test, which consists of smoke pellets being placed in a sealed-off fireplace, will expose any flue leaks.

Benchmark certificates

New boilers come with blank certificates that need to be completed by the installing and commissioning engineer. If the boiler is gas-powered, the engineer’s CORGI membership number should be added.


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