July 2023
Frequently Asked Questions
Following the public meeting on the 29th June 2023 and email communication over recent weeks we wanted to set out answers to the most common questions here. This covers questions relating to Phase One, Phase Two, demolition plans as well as other, wider issues relating to Darwin Green.
If you have a question not covered here, please get in touch by using info@darwingreenconstruction.co.uk
Phase 1
General
Is my home at risk of foundation failure?
No. The issues affecting Phase Two properties are not found at Phase One and we are confident that there are no quality concerns. We appointed Cundall and Simpsons TWC, both expert independent engineers, to conduct thorough investigations into the design and NHBC inspections of homes built in Phase One. These reports confirm that the design issues affecting Phase Two properties are not found at Phase One and there are no quality concerns.
In addition, to offer further reassurance, we have decided to provide homeowners in Phase One with a 15-year structural warranty for each property which will commence on expiry of the 10-year NHBC structural warranty, meaning that each home has the benefit of structural warranty cover for 25 years.
When and how did you become aware of the issue?
In recent months, as part of our regular quality checks, we identified some early signs of foundation stress at a small number of Phase Two properties. We immediately halted construction and appointed third party engineers to conduct a thorough investigation, which identified issues with the design of foundations of Phase Two properties.
Independent review
Can an independent review be done of the foundation designs?
We are prepared to fund (to a reasonable amount to be approved) a further independent review of foundation designs for Phase One, to an agreed scope by an appropriately qualified and accredited engineer. We have provided two independent reviews to date but recognise that residents may want to appoint their own engineers and we are happy to suggest accredited engineering companies if helpful.
Can an independent suitably qualified and experienced building inspector review the photographic records of the plot by plot checks and inspections of excavations of the as built foundations?
The two independent engineering reports that were undertaken by Cundall and Simpson TWC were rigorous and included reviews of the NHBC inspections records as well as the foundation designs which confirmed there are no concerns on Phase One. However, we understand that residents may want a further review and we are prepared to help with funding, to a reasonable amount. As outlined in the public meeting, we do not produce as-built drawings as we build to the designs.
Foundation designs
Can Phase One customers have a copy of the foundation design for their own home?
We have provided diagrams setting out the foundation designs for the homes on Phase One. As we have stated these have been subject to two independent engineering reviews, which have highlighted the fundamental differences known between Phase One and Phase Two foundation designs. NHBC is happy to provide inspection records for Phase One completions. All of the homes were signed off by building control including a structural warranty – which we are extending. We don’t hold “as built” drawings.
Can you provide evidence-based reassurance that the as built foundations were constructed as specified?
We do not produce as built drawings as we build to the designs. Two independent engineers have confirmed that there are no issues with foundations on Phase One. All of the homes were signed off by the NHBC, who can provide inspection records, along with a structural warranty – which we are extending to 25 years for added reassurance.
Can you explain why there appears to be differences between the minimum foundation depths of 0.9m or 1m? Please clarify why the 0.9m depth was considered to be appropriate?
The two numbers are for River Terrace Deposits and Gault Clay respectively, which are medium and high volume change potential. Hence the two values. If foundations were within a significant thickness of River Terrace Deposits, the lower value can be adopted.
Were there any building regulations changed during 2012 & 2021?
There were no regulation changes that affected the approach to foundation or sub structure design.
Reviews undertaken by Cundall and Simpson TWC
Did Cundall review the as built design as well as the design proposals?
No. Cundalls, an independent and expert engineering consultancy, reviewed the foundation designs plus the extensive inspection reports from the NHBC. They confirmed that there were no concerns with the foundations on Phase One.
Reading the description of the different designs for Phase One and Phase Two on page 4 of the Simpson report, it appears that it is not the foundation as such that has caused the problem on Phase Two. Instead it is the method by which the flooring has been installed above it (in-situ suspended concrete slabs on Phase Two as opposed to suspended precast beam and block ground floor system on Phase One). In the case of Phase Two, this has not allowed for the expected “heave” in the soil which has resulted in damage to the buildings. Can you confirm whether the concrete foundations themselves below this flooring installation (trench fill specifications) are also different between the two designs (in terms of materials used and installation), and if, so how?
This is correct – we have used foundation as shorthand covering both the foundation and flooring design. The actual foundation design solutions across the two phases are similar, with bearing depths influenced by local geotechnical data, influence of existing and proposed landscaping. As both Cundell and Simpson TWC highlighted, the design was suitable for Phase One and therefore are confident that there are no concerns.
Can you re-issue the Cundall Report with the typo of 300m, changed to 300mm?
This has now been done and can be viewed here.
Will you provide the documents referred to in the engineers’ reports?
We listed these documents to show the breadth and rigour of both Cundalls’ and Simpson TWC’s investigation and that their conclusions were based on a range of evidence. However, we aren’t planning to provide them more widely. All relevant information from these documents has been included in their reports, which we have shared with residents and are available on our website.
Section 1.1 of the report states that; “It is assumed that the designs have been constructed as shown on the information provided”. Please could you confirm whether or not the houses were all constructed as per these designs? On a related note there is consistent use in the report of the term “foundation design”. Please confirm if this term means the foundations as built or the foundations as proposed.
The foundations were all built to the designs and regularly inspected through our quality assurance processes and by the NHBC, with the homes signed off when complete by building control. For added reassurance, we are also extending the warranty for residents living on Phase One to 25 years.
Page 100 of the PDF and a home buyer’s report shows that the whole of Phase One and Phase Two is at moderate risk of subsidence.
We have experience of building more than half a million homes across England, Scotland and Wales over the last 65 years and this report would be no different to many other areas of the country. We have phase/site specific geotechnical survey for Darwin Green, which does not raise any specific risk associated with subsidence. We are confident that the geotechnical data received on the back of the trial pits, boreholes etc concludes the gault and river terrace deposits encountered on site provide sufficient bearing capacity for the foundation solutions designed.
NHBC
Who are the NHBC and what is their role?
The NHBC are the UK’s leading independent provider of warranty and insurance for new-built homes. They offer the Buildmark policy, which includes a 10 year structural warranty, for around 1.5 million homes across the UK. To sell homes covered by Buildmark, registered builders and developers must comply with the requirements set out in the NHBC Standards. More information is available on the NHBC website: https://www.nhbc.co.uk/
You say there were more than 1,700 NHBC checks of homes on Phase One, what did they consist of?
Every home we build is regularly inspected by the NHBC, who provide building control and warranty services. On Phase One, there were more than 1,700 physical inspections of the homes, demonstrating the rigour and level of quality assurance that goes into building a new home. A home will not be signed by the NHBC as complete, which is required for the ten-year structural warranty, unless the NHBC is comfortable that the home meets the required standards.
Can I have the NHBC Inspection log for my home?
We understand that you may want to see the NHBC inspection logs for your home. To make this easier, we can help supply plot specific inspection logs to homeowners. Please contact Vicki Hart on vicki.hart@bdwhomes.co.uk to make this request.
NHBC approved the various stage inspections and the initial plans on Phase Two, does that mean that the checks were not carried out correctly or an error was made in approving the design?
No home on Phase Two had been signed off as complete by the NHBC. The issues were caused by the foundation designs for Phase Two, which were identified by our quality assurance checks as early signs of foundation stress became visible. As soon as this was noticed construction was halted immediately to allow us to investigate further.
There is a publicly available NHBC form covering heave precautions, which sets out information to be supplied on the foundations. Is this available on a plot by plot basis?
This relates to the various NHBC standards which are readily available on the NHBC website. The designs are produced based on geotechnical data, this is then used as the basis for the structural designs which is cross referenced to NHBC standards, interrogated by their engineers to then get to a position that these are accepted. There is considerable information that is produced as part of the detailed design package. This is produced by structural engineers, civil engineers, architects, specialist suppliers and is cross checked, coordinated by the technical team and submitted to NHBC for their acceptance. There has been no sign of stress or failure on Phase One and two independent engineering firms have confirmed there are no concerns. If anybody wants a copy of the NHBC standards that are available on the website please request from Vicki Hart.
Warranty
Is the extended warranty backed by an external body?
As added reassurance, we have decided to offer customers on Phase One an additional 15 year structural warranty on top of the cover provided by the NHBC. This will be provided by Barratt Developments PLC and will take the total cover to 25 years, remaining with the property throughout the term. Further details will be sent out to customers next week (week commencing 17 July).
Will the extended warranty provide an extension of the NHBC cover or just foundations?
It will provide a 15 year extension to the NHBC cover. Further details will be provided next week (week commencing 17 July).
Other
A detailed report was carried out following reports of cracks in the garden of Beagle Road in August 2022. While that point was resolved at the time, why were similar inspections not carried out on Falmouth Avenue?
Although the ground conditions are similar, the homes that front Beagle Road and back onto the Phase Two are in direct influence of the hawthorn hedge (note foundation designs have been designed and built to include adequate heave protection). The influence of the hawthorn hedge coupled with the gault clay was the primary issue for cracking in the gardens. It is worth noting that although some ground movement has occurred (and been recognised through the further Site InvestigationsI) to the rear gardens, the fact that this has not translated into any issues with the building structure should provide assurances that the substructure has been designed appropriately for the ground conditions.
We’ve noticed cracks in the Block C cycle store, what is the cause of this?
The cracks in the cycle store are generally vertical and pass through blocks as well as joints. The cracks are consistent with shrinkage cracks and do not indicate any structural movement.
Phase 2
How did this happen?
Investigations are ongoing and as you would expect we may be taking legal action so we can’t speculate at this stage however there was a fundamental problem with the designs of the foundations on Phase Two at Darwin Green. As soon as we identified some early signs of foundation stress at a small number of Phase Two properties, we halted construction and appointed third party engineers to conduct a thorough investigation, which identified those issues with the design of foundations. We are sorry for the impact that this has had on our customers and wider community.
How are you supporting the customers who had reserved properties?
We are in close contact with our customers. We have given those affected the option to either cancel with a refund of costs to-date, or to continue with their reservation with a commitment that we would meet any additional costs they incur as a result of the delay. We are pleased that a significant number have confirmed they wish to proceed with their purchase, either of the property they had reserved or elsewhere at Darwin Green. Any customers can get in touch with Will Phair, Sales Director, william.phair@bdwhomes.co.uk, should they have any questions or concerns.
Will residents of Phase Two get an extended warranty?
Whilst the designs will be different when Phase Two has been re-built, we thought that the suggestion made at the public meeting for all Phase Two customers continuing with their purchase to receive the extended 25-year warranty was a very good one. We will be writing to customers with more detail on the warranty soon.
Will you consider using local authority building control for Phase Two?
Yes, we are considering our options, and we will update again shortly.
We understand from conversations with Cambridge City Council that the investigations into Phase Two failure are still ongoing?
We can confirm that the Council’s investigations are complete. Two independent reviews have also been undertaken by third-party engineers, confirming that the issues were caused by the design of the properties on Phase Two. However, we understand that residents may want to conduct their own investigation, and we are willing to fund (amount to be agreed) a further independent review.
Demolition and re-construction
When will we know more about the demolition plans?
We will be sharing more details on how we will demolish and remediate the homes soon, but we are working closely with the local authority to ensure that the approach and method minimises any impact on you and your neighbours. We will share these plans with you and will share actions before they happen.
Do you need planning permission to demolish and rebuild the homes on Phase Two?
We are still working through our plans with the local authority, which we will share as soon as they are available. This will include whether planning permission is required. However, we are committed to minimising any impact on the wider community and the environment, and will keep neighbours and residents fully informed on these plans and as work starts.
When will demolition start?
We are still working on the plans and will let you know the detail as soon as possible. In order to develop the right approach, and agree our plans with the local authority, we expect it to take at least another month before we will be able to communicate the details of our demolition strategy. However, we will communicate fully and ensure the approach minimises any impact on you and the wider environment.
Will you be recycling materials from your demolition?
Yes, wherever possible, we will recycle materials from the demolition. We are the UK’s leading national sustainable housebuilder, and so we will do all we can to ensure the demolition is done in as a sustainable way as possible.
Can we keep all construction traffic away from residential areas?
All construction traffic is being directed to access from the A14 end of the site.
Will you consider compensation for Phase One customers for the demolition nuisance?
Our focus is to limit and mitigate the nuisance for existing residents as we work with the local authority to put in place the demolition strategy. It is too early to talk about compensation at this stage.
Darwin Green
Community infrastructure
Can the ditch be cleared behind Woodlark Road and the levels on this area of the site be checked?
The work started on w/c 10th July and will be completed as soon as possible.
Can the MUGA be opened?
We understand residents’ frustration and we have committed to open the MUGA by the 4th August.
Who can I contact about these issues?
We have appointed Operations Director Adrian Jarman to oversee the demolition and construction at Darwin Green. As well as Phase Two work, he will be the main point of contact and Project Manager for Darwin Green ensuring that issues like the ditch at Woodlark Road are resolved quickly. Please contact info@darwingreenconstruction.co.uk. With any questions or issues, or you can contact Adrian directly on adrian.jarman@barratthomes.co.uk.