Extension costs: Wraparounds
Adrian Wild sets out costs for this type of addition
End-of-terrace and semi-detached houses, particularly those of the Victorian and Edwardian eras, often have space to the side of the property. In many cases this is little more than a dead, awkward alleyway. Adding a side-return extension can reclaim this unused zone. Combine it with a rear addition that wraps all the way around the property, and you’ll have the opportunity to maximise your home’s footprint.
For most homeowners the priority is to create a large, open-plan and multi-functional zone, such as a kitchen/ dining/living area. So single-storey wraparounds are more common than multi-storey versions. The impact of a wraparound can be considerable, completely altering the feel of the ground floor – so it offers the chance to revamp the connection between house and garden.
The indicative costs given here were generated by the Build It Estimating Service. They’re based on a single storey addition to a terraced property, suitable for a kitchen. The gross internal floor area (GIA) of the resulting space will be 25m2, including the existing section of the house that the extension is being wrapped around. Prices include all the infrastructure (including cooker and socket circuits, hot and cold water supply, and extension of the heating system).
As this is a terrace, there will inevitably be some access issues, so a labour allowance for hand digging has been factored into the calculations. Structural works to support the upper storey corner wall to open up the ground floor space has been included. Any further structural opening from the main property would be an additional cost – as would internal walls, flooring and the kitchen fit-out (all of which can vary significantly depending on specification). You’ll see that since there is relatively little roofing, a flat roof extension costs only slightly less than the two pitched examples.
Our standard specification is based on a brick and block extension with PVCU windows and standard patio doors. The flat roof would be in torch-on felt, while pitched versions are based on concrete tile.
The optimised spec demonstrates what you might expect to pay for upgrading the project. It’s based on stone and block construction, aluminium windows and bifold doors. The optimised flat roof option features a roof lantern and GRP roofing, while the pitched designs include a vaulted ceiling, rooflights and clay plain tile finish.
These prices take in the builder’s overheads and profit, as well as VAT. If you did the work DIY, you might save as much as 50% on total costs; but at the expense of your own time and the risk of missteps along the way. Potential additional costs include architect’s plans (if you’re taking this route), clearing the site and moving services (such as drainage).
Flat roof wraparound
A low-level flat roof addition is a good option in order to avoid impinging on views from the upstairs rooms of Victorian properties. Rooflights and lanterns can be incorporated into the structure to add wow factor and create a real sense of space, potentially assisting in providing daylight to the main body of the house as well as the extension.
Apex roof wraparound
This style has two roof slopes that come together at a ridge; so the wall is triangular at the top. An apex extension is as much about going up as out; the vaulted ceiling provides a spacious and impressive room. For maximum visual impact, windows can be stretched along the ridgeline of both roof elevations and extra glazing fitted above sliding doors.
Hip abutment wraparound
A hip roof has three sloping sides, all of equal pitch, descending from a ridge at the top. This style of extension can be designed so that the central ridge sits between upper storey windows, preserving vistas thanks to the angle of the slopes. The roof plane at the rear elevation also allows you to build further into the garden before views are compromised.