Advice and costing for building a roof terrace on a pitched roof

Hello there. We recently purchased a lovely 3 bed flat over the top two floors of a terrace in SE London. Our landing looks out over the kitchen. Ideally we'd love to transform this into a roof terrace in the coming years. Obviously this would involve altering the roofline, as the existing roof is pitched, and adding a door to the landing. One of our neighbours with a similar terrace has done this with their roof. We're first time buyers and absolutely clueless, so at this stage I'd just like to feel out who we should be speaking to and how much we need to save.

Comments (4)

  • Rowland
    5 days ago

    hi Rachel,

    congratulations on your purchase!!

    in order to put the flat roof onto the potch you firstly will need to apply for planning permission. This consists of submitting drawings for the proposed roof terrace with details for balustrade to protect the edge.

    the planners will consult with neighboirs and assess the amount of overlook okk ng that the proposal creates, you may consider shielding the overlooking with screening as part of the application to avoid having the application rejected.

    once you have been through the painful planning approval the building work will consist of building up the walls and removing the pitched roof possibly renewing ceiling joists to the roof below and certainly adding straps to the joists and putting the new flat roof . you will also nee to add an access door to the newly created terrace.

    this is likely to cost you between 10k - 15k .

    Finally you will first and foremost seek the free holders permission. so there will be probably be costs associated with getting this permission in place unless you have a shared freehold, which makes the process a matter of seeking approval of your joint free holders.

    I hope this helps!!



    Rachael Kendrick thanked Rowland
  • Frank
    3 days ago
    last modified: 3 days ago

    hi Rachel,

    All that Rowland said, plus a little procedural hint once the "other" permissions (freeholder, and neighbour underneath that roof) are in and you work on your plans:

    Before jumping right in and submitting for planning permission, do a little research. This means a few things:

    1. Most councils will have planning applications online - they need to be publicly (re)viewable for a few weeks before decision anyway so others can comment. Often with a map or postcode search. Read them, in your area, find some that previously applied _successfully_ for the creation of a roof terrace. These give a good idea what the planning office focuses on. "because my neighbour has one" is not commonly seen sufficient, at least not in London.

    2. Read your council's planning policy documents, what these say about roof terraces, balconies or verandas. Note that even a blanket "... not permitted" only means "not being waved through without convincing reasons". But it is good to be aware what rules apply, particularly in areas of outstanding beauty, for listed buildings or in conservation areas.

    3. Again, most councils offer an informal consultation (~30mins phonecall) with a planning officer, to talk about "ideas". When you've done your research and have a good plan what you hope to build, arrange for that. Ask openly - what sort of thing has the council approved in the past, what would take care of the usual concerns, how can we improve things for the community. Get a feel for the type of project submission they see positively. This should give you an idea whether your plans should "sail through" or are more likely to face opposition.

    It's harder to appeal a refused application than it is to file a "more verbose" one in the first place.

    Rachael Kendrick thanked Frank
  • Rachael Kendrick
    Original Author
    2 days ago

    Thank you so much! This is great advice. That roof is actually over our kitchen, and we have 2/3 of the freehold of the building. I'll start doing my research now.

  • PRO
    6 hours ago
    last modified: 6 hours ago

    I agree with all the advice above and would add, when you have the plans, consider going to see your neighbours in person, (especially the one which will be most affected). Do this before the plans are submitted, or if you have a diplomatic architect, ask them to speak to your neighbours to just talk them through what you plan to do. It usually goes down better than the planning consultation letter just landing on their laps. If they ask, don't feel you have to agree to any concessions there and then, tell them that you don't have any expertise but "of course you can discuss it with your architect". Leave the architect to handle anything contentious as you want to remain on good terms with your neighbour and the architect won't have anything to loose as they don't have to live next door to them.

    When it comes to the building work, ensure that there is excellent insulation in the roof. There are now super thin insulations that are effective (if you need it to be thin) but go for more than the regs require. Also ensure that the roofing is done superbly, good flashing details, adequate falls etc as this is what lets down roof terraces. Ensure that there is power, water (power safely near the water for irrigation if that is what you are going to have) and if you need it check your internet signal and provide a booster (perhaps in the hall) if it is not good enough. This summer has shown that outside workspace can be a real benefit. When it comes to the finish material, consider Millboard (https://millboard.co.uk/samples) I used the 'enhanced grain' finish. I have used it on three jobs and I am very happy with this relatively lightweight, low maintenance, good quality (not cheap) product. Ensure that there is access to inspect the roof should you need to and clear leaves (it is amazing how many will find their way in-between even tiny gaps) You will probably need less light than you might think (consider your contribution to light pollution). Consider if you can have solar powered lights and water capture for watering plants and avoid outdoor speakers as these really will annoy your neighbours. I love roof terraces as they are usable for so much of the year, often warmer than a lower garden in the winter. Good luck with it. Regina.

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