There is considerable interest in the provision of rooftop housing developments (RTD) to help alleviate the housing crisis – agent Knight Frank estimates that 40,000 homes could be built on top of existing buildings in Central London alone – however a seminar by Pellings the London and South East based integrated design, property and construction consultancy, warned that careful planning is required.
Nigel Goddard of Pellings and one of the speakers at the seminar emphasises this point: “Following the Mayor of London’s support of rooftop developments and the recently published NPPF guidelines stating that planning authorities support well designed and appropriately scaled RTDs, there is a clear opportunity to create more residential units on top of existing housing.
“But it is not like building on a cleared site. You can think of RTD as a new build project with its foundations many metres in the air and as the extension of an existing building, and the solution requires skills and experience from both perspectives,” he adds.
Pellings has analysed the challenges RTDs face and developed hybrid solutions for what is in effect a hybrid problem. Goddard who has been leading an RTD programme for a London Authority at Pellings has created a 10-point plan for social housing landlords considering rooftop housing includes:
Identifying key drivers: condition of the existing building, housing need, airspace opportunities and S.106 obligations.
Initial viability studies: undertake water, drainage, gas, and electricity surveys and capacity of lifts, parking, play and landscaping areas and tenure mix.
Occupancy issues: Leaseholder and tenancy positions including statutory consultation, service charge issues, loss of amenity, and increased noise.
Technical validation: These include Health and Safety, means of escape, sustainability studies and energy performance.
Planning and statutory issues: including space standards, wheelchair access, floor-to-ceiling heights and apartment orientation.
System selection: consider the most appropriate system whether off- or on-site construction methods.
Contracts and procurement: Consider design and build and contractor selection.
Technical specifications: Use NBS/NHBC and other guidance, avoid over innovation; insure good M&E integration by using BIM.
Guarantees: be clear on the guarantee requirements and engage early.
Cost and risk: Develop a full elemental cost plan and costed risk register with evaluated risk reduction/mitigation measures at all stages of the design and works procurement for the project.
Goddard concluded: “Rooftop development can surely make a meaningful contribution to the supply of housing but a considered and structured framework for assessing the viability of a project is required by those who understand the pitfalls as well as the potential benefits.”