Can I Build a Terrace on My Roof?
The desire for extra outdoor space at home has probably never been greater. Could a roof terrace be the answer?
Whether you have an existing roof ripe for conversion or want to capitalise on your new extension’s flat surface, making it accessible from a room above, the idea of a roof terrace can be appealing. And if you have a suitable roof, it also seems like a no-brainer to fill it with plants and deckchairs.
Planning, however, can be tricky, and there are structural considerations, too. So is the idea worth pursuing? Three terrace-savvy professionals share their expertise.
Professional advice from: Stephen Fletcher of Stephen Fletcher Architects; Francesco Pierazzi of Francesco Pierazzi Architects; Marco Guarnieri of Guarnieri Architects; Calum Duncan of Calum Duncan Architects
Planning, however, can be tricky, and there are structural considerations, too. So is the idea worth pursuing? Three terrace-savvy professionals share their expertise.
Professional advice from: Stephen Fletcher of Stephen Fletcher Architects; Francesco Pierazzi of Francesco Pierazzi Architects; Marco Guarnieri of Guarnieri Architects; Calum Duncan of Calum Duncan Architects
How might a good architect be able to persuade the council and convert even a tricky roof?
“[It can be possible to get planning] by being imaginative and sometimes thinking outside the box,” Marco says. “The architect will need to prove to the council that there’s no impact on neighbours and that [the new terrace] sits well in the urban context.” That might sound tricky, but he adds, “We’ve managed this in conservation areas.
“A flat roof will lend itself best to be converted, but I think there’s a good roof terrace project for any roof,” he continues. “There’s no limit on what can be achieved from a design and engineering point of view. The main driving criteria are what can be achieved in planning and what the homeowner’s budget is.”
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“[It can be possible to get planning] by being imaginative and sometimes thinking outside the box,” Marco says. “The architect will need to prove to the council that there’s no impact on neighbours and that [the new terrace] sits well in the urban context.” That might sound tricky, but he adds, “We’ve managed this in conservation areas.
“A flat roof will lend itself best to be converted, but I think there’s a good roof terrace project for any roof,” he continues. “There’s no limit on what can be achieved from a design and engineering point of view. The main driving criteria are what can be achieved in planning and what the homeowner’s budget is.”
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Can I create a roof terrace on…
…my existing flat-roof outrigger on a Victorian terraced house?
With planning, yes, although Francesco explains, “The roof itself may need to be re-supported or strengthened to take the extra weight, and perhaps resurfaced with more suitable waterproofing materials.”
…my existing flat-roof outrigger on a Victorian terraced house?
With planning, yes, although Francesco explains, “The roof itself may need to be re-supported or strengthened to take the extra weight, and perhaps resurfaced with more suitable waterproofing materials.”
…my existing pitched-roof outrigger on a Victorian terraced house?
With the same proviso regarding permission, Francesco advises, “Possibly as an inset roof terrace.”
Read reviews of architects and building designers in your area in the Houzz Professionals Directory.
With the same proviso regarding permission, Francesco advises, “Possibly as an inset roof terrace.”
Read reviews of architects and building designers in your area in the Houzz Professionals Directory.
…my new flat-roof rear extension?
If the roof has permission to be used as a terrace, all the experts agree, then yes. This will almost certainly need to be part of the design and build from the start, though, due to the structural considerations, which are expanded upon below.
If the roof has permission to be used as a terrace, all the experts agree, then yes. This will almost certainly need to be part of the design and build from the start, though, due to the structural considerations, which are expanded upon below.
What are the costs to consider when converting an existing roof?
“This depends on the size, finishes and structural requirements,” Marco says. “It also depends on what additional work you need to do – ie, new access glazed doors, drainage and so on.
“Generally, professional fees for the design of a roof terrace may be between 15% and 20% of the construction cost,” he says.
“This depends on the size, finishes and structural requirements,” Marco says. “It also depends on what additional work you need to do – ie, new access glazed doors, drainage and so on.
“Generally, professional fees for the design of a roof terrace may be between 15% and 20% of the construction cost,” he says.
What are the structural requirements?
“Homeowners often don’t realise that turning a flat roof into a terrace is not a straightforward operation,” Marco says. “The roof is just a roof and, while you may get planning for it, you may need to adequately reinforce that roof to pass Building Control structural requirements.”
Francesco agrees. “The structure needs to be designed to take the extra loads a roof terrace calls for, which are by default greater than the design loads for a simple flat roof,” he says.
“The joists/RC [reinforced concrete] slab needs to be sized accordingly by the structural engineer,” Stephen says. “And, as well as the weight of people/plants/furniture, one needs to consider the weight of the flooring – for example, decking or paving.”
“Homeowners often don’t realise that turning a flat roof into a terrace is not a straightforward operation,” Marco says. “The roof is just a roof and, while you may get planning for it, you may need to adequately reinforce that roof to pass Building Control structural requirements.”
Francesco agrees. “The structure needs to be designed to take the extra loads a roof terrace calls for, which are by default greater than the design loads for a simple flat roof,” he says.
“The joists/RC [reinforced concrete] slab needs to be sized accordingly by the structural engineer,” Stephen says. “And, as well as the weight of people/plants/furniture, one needs to consider the weight of the flooring – for example, decking or paving.”
Any other considerations?
Stephen points out the requirements for balustrades, which need to be 1.1m high, and adds that French windows may require toughened safety glass.
“Sometimes, to achieve a flush internal/external threshold, one needs to consider the height of the flooring above the roof structure for waterproofing,” he says. “Decking and paving can be installed on pedestals (which are available in varying heights). These allow the drainage to run between the joints.”
Marco raises the issue of fire regulation requirements. “Adding a roof terrace to a home is like adding a room, so it needs to be considered in this context, too. The room from which you access the roof terrace becomes an ‘inner room’. The terrace [the ‘outer room’] on the roof extends the distance to the main exit from the building, which, in a terraced house, is the front door.” Fire exit access will be closely examined by Building Control.
Stephen points out the requirements for balustrades, which need to be 1.1m high, and adds that French windows may require toughened safety glass.
“Sometimes, to achieve a flush internal/external threshold, one needs to consider the height of the flooring above the roof structure for waterproofing,” he says. “Decking and paving can be installed on pedestals (which are available in varying heights). These allow the drainage to run between the joints.”
Marco raises the issue of fire regulation requirements. “Adding a roof terrace to a home is like adding a room, so it needs to be considered in this context, too. The room from which you access the roof terrace becomes an ‘inner room’. The terrace [the ‘outer room’] on the roof extends the distance to the main exit from the building, which, in a terraced house, is the front door.” Fire exit access will be closely examined by Building Control.
Marco also highlights something he says homeowners often miss: the additional opportunities that come with a roof terrace project.
“It’s not only about forming the terrace; in creating a larger opening to access the terrace, there will be additional benefits, such us brightening the interior and visually extending it onto the roof terrace.”
It’s a point well illustrated in this project by Calum Duncan Architects. Here, you can just see (through the window) the new doors that open onto the terrace from the kitchen, and imagine the transformation to that narrow space, especially during the the summer when they’d be open a lot of the time.
“It’s not only about forming the terrace; in creating a larger opening to access the terrace, there will be additional benefits, such us brightening the interior and visually extending it onto the roof terrace.”
It’s a point well illustrated in this project by Calum Duncan Architects. Here, you can just see (through the window) the new doors that open onto the terrace from the kitchen, and imagine the transformation to that narrow space, especially during the the summer when they’d be open a lot of the time.
Here’s the terrace as seen from below.
Tell us…
Do you have a roof terrace? Would you like one? Share your experiences and thoughts in the Comments.
Tell us…
Do you have a roof terrace? Would you like one? Share your experiences and thoughts in the Comments.
“The chances depend on the particular context of where you want to create it and the impact it will have on neighbours,” Marco Guarnieri says.
Stephen Fletcher expands. “If it’s close to neighbouring properties, the planners are unlikely to be amenable, due to potential overlooking and noise issues,” he says. “However, sometimes there’s already a precedent in the area with other adjacent roof terraces.”
Francesco Pierazzi adds that these nearby terraces would, of course, need to have been legally permitted in the first place, but that, in built-up areas such as London, the rules are much tighter.