Code for sustainable homes – hydrology reports towards sur1 and sur2

All new social housing schemes in England must have a Code for Sustainable Homes (CSH) rating. While many local authorities in England are requiring the Code for Sustainable Homes to be met as a condition of the planning for private housing schemes.

We assist Clients, Architects and others involved in projects to identify or design sustainable drainage and flood risk mitigation works and advise on compliance and performance against the categories Sur 1 (Surface Water Run-off) and Sur 2 (Flood Risk).

The Code for Sustainable Homes was introduced in 2008 and has had a mixed take up in the industry. 

The code for sustainable homes is the national standard for the sustainable design and construction of new homes. It aims to reduce carbon emissions and promote higher standards of sustainable design above the current minimum standards set out by the building regulations.

Sur1 and Sur2 Code for sustainable homes

How is a code for sustainable homes hydrology assessment – sur1 and sur2 priced?

Every site is unique, with specific challenges and opportunities. We look to work with you, to maximise your advantages through good design and advice. 

We don't quote "success rates" or "offer 2 for 1 deals" or "price match on a like for like basis" or other unprofessional practices more suitable for supermarkets, not a professional consultancy.

We will assume you want a professional service at a competitive price.

Sur 1: This is the Management of Surface Water runoff from the development

Mandatory Elements:
•    Statement from the appropriately qualified professional confirming that they are qualified in line with the Code definition. Such as Wilsham Consulting.
AND
•    The appropriately qualified professional’s report containing all information necessary to demonstrate compliance with the peak rate of run-off and volume of run-off requirements

The sur1 and sur2 report should include:
•    Areas of permeable and impermeable surfaces on the site pre- and post- development.
     Where the impermeable area has increased post development, the report should also include:
a)    Details of the permeability characteristics of the site pre- and post-development (e.g. infiltration tests etc where appropriate)
b)    Peak rates of run-off (l/s) calculations for the 1 year and 100 year events, pre- and post-development, including an allowance for climate change over the development lifetime
c)    Detailed documentary evidence showing the methods used to reduce the peak rate of run-off to pre-development rates.
d)    The pre- development volume of run-off (m3) for the 100 year 6 hour event.
e)    The additional volume of run-off (m3) for the 100 year 6 hour event caused by the development without mitigation measure.
f)    The additional volume of run-off (m3) with the proposed mitigation run-off (m3) .

Information to demonstrate that the hierarchical approach to reducing the additional volume of run-off was followed

1.    Information on the calculation methods used, as well as summary results

2.    A Flood Risk Assessment confirming the risk of flooding from all sources of flooding (this may be contained within the appropriately qualified professional’s report)

3.    Drawings showing the pre-development drainage for the site (natural or constructed).

4.    Drawings showing the proposed drainage solution, system failure flood flow routes, potential flood ponding levels and ground floor levels.

5.    Confirmation from the appropriately qualified professional that local drainage system failure would not cause an increase in the risk of flooding within dwellings either on or off site.

6.    The appropriately qualified professional’s report detailing the design specifications, calculations and drawings to support the awarding of the credit(s)

Sur1 and Sur 2 CSH

What is meant by an appropriately qualified professional?

A professional or team of professionals with the skills and experience to champion the use of SuDS within the overall design of the development at an early stage.

Clearly that rules out most, if not all – Clients, Architects, Structural Engineers, Builders and others involved with building projects.

Wilsham Consulting is one of the few and leading practices in the whole of the UK with the necessary experience. Our Director – Stephen Gibson is a UK expert, presenting at the last International Sustainable Urban Drainage Conference SUDsnet and advises on the drafting of CIRIA guidance on some water related issues (CIRIA C609).

•    The professional or team of professionals must be capable of understanding the site’s particular surface water management needs and opportunities.
•    They must have knowledge and experience in using SuDS-based solutions to influence the holistic design of a development’s drainage system and provide the robust hydraulic design calculations referred to in key guidance documents such as The SuDS manual (CIRIA C697, 2007) and Preliminary rainfall runoff management for developments (EA/DEFRA, 2007). 

Sur2 : A professionally produced Flood Risk Assessment

The aim is to promote housing development in low flood risk areas, or to take measures to reduce the impact of flooding on houses built in areas with a medium or high risk of flooding. The scale (and cost) of the FRA will depend on the scale of the development and the site specific risk.

Typically two credits are available for developments situated in EA defined Zone 1 – low annual probability of flooding (as defined in PPS25 Development and Flood Risk) and where the site-specific Flood Risk Assessment (FRA) indicates that there is low risk of flooding from all sources.

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