What other consultants may be required for your house extension.
Sometimes the home owner or their building design agent may have to engage the
services of external consultants usually required to compile specialist reports to support their Planning or
Building Regulations applications in order to gain an approval.
Here is a list of the more common situations that may require the home owner to spend extra money on these
FLOOD RISK ASSESSMENT - If your property is within a defined flood risk area (river, sea or
rain water run off) then the Environment Agency (EA) will be consulted. Sometime they require a flood risk
assessment to be completed in accordance with PPG25. Other times, the EA deem home extension work to be low
risk and they simply do not have the resources to comment on every single home owner extension scheme.
Alternatively your Local Planning Authority (LPA) may request a simplified flood risk assessment to be completed
irrespective of the EA's comments.
The Flood Risk Assessment to PPG25 standard can be technically challenging for some home extension designers and
there are specialists in this field who will gladly do this for a fee. When you have read one you will see
that it is yet another jargon filled navel gazing exercise in complete useless chaff that could be summarised into
3 paragraphs by most practically minded people. However, this does not satisfy most academics who have
control over your building scheme.
The simplified version of a flood risk assessment is easier to achieve and many Councils have worked
examples that you can follow and apply to your own scheme. In essence its all about identifying the flood
risk source and implementing workable and practical measures within he new build element to
eliminate or reduce the risk of damage, clean up and health and safety.
Therefore if you can have a raised ground floor level above the formal flood level, allow openings under
the ground floor to allow for the free flow of flood water, have electrical services that drop from the first
floor rather than at low level, have solid floors rather than timber, incorporate a dry access to the property for
means of escape, have a first floor as a refuge location etc. then incorporate it within your scheme. If some
of the items are not practical to incorporate then at least discuss it and state why it is not possible then
you have generally complied.
BAT REPORT - Sometimes your scheme may involve the removal of an old external building and if
bat roosts are known within your area then the Council will have a planning policy that seeks a specialist
report that it has been checked and that there are no bats as they are a protected species. There are
specialists that can do this for a fee. If they find bats you scheme can be denied. You may be
required to use the roof void of the extension to encourage bats.
DESIGN AND ACCESS STATEMENT - There is a government standard on what is to
be covered in a design and access statement which is for large development schemes. Most of the headings stated are
not relevant for domestic home extension work and each local planning authority (LPA) will have their minimum
requirements for what is to be covered.
Most house extension designers are well capable of writing a Design and Access statement to support your
planning application scheme but for some Councils and locations it may go outside of their expertise. If
an LPA has a large number of conservation areas and listed buildings, they will require a much higher level of
detail and discussion with their Design and Access statement and a recent government revised guidance on this
endorses a more 'ferensic approach' even for home extensions.
Essentially you have to identify any impact that your proposal may have on each of the Councils heritage assets
near the extension (listed buildings) And explain why it will not be an adverse impact affecting the listed
IMPACT AND / OR SUSTAINABILITY ASSESSMENT - Some councils require an 'impact or sustainability
assessment' for a house extension scheme and again most home extension designers are able to put into words some
'planning speak' that will satisfy the planners desire for jargon.
SAP ASSESSMENT / THERMAL EFFICIENCY REPORT - Some home extension schemes will have a net new
glazing area that will exceed 25% of the extension floor area. This means that you will have to obtain a heat
loss calculation from an approved SAP assessor who uses an approved piece of government endorsed software to prove
that your 'as designed building' is as efficient as a compliant 25% glazed extension. This often
means incorporating upgrades to the thermal efficiency of the building structure and replacing the outdated boiler
in mitigating for the extra less efficient glazing. This is required to support your Building Regulations
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