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

3 years ago

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.

Featured Answer

Rowland

3 years 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!!

best

Rowland

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Comments (11)

Frank
3 years ago
last modified: 3 years 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
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Rachael Kendrick
Original Author
3 years 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
Architects
3 years ago
last modified: 3 years 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.
Rachael Kendrick thanked Architects
PRO
Room-by-Room (UK) Ltd
3 years ago
Hello Rachael,

Congratulation

I recently designed a roof terrace for a client in Hertfordshire. The main issue that we had was with overlooking the neighbours properties. This was complex and time consuming to resolve taking almost 12 months to get the planning approval.

Can I assume that the proposed scaffolding will include a temporary roof covering to ensure the structure remains watertight when the roof comes off? If so the scaffolding legs will probably be positioned on land that you may not own. Therefore as the intended work is not maintenance but new construction a party wall surveyor may need to be employed to deal with this aspect. Bearing in mind that you will be responsible for the cost of all the agreements, this could be quite a cost just on paperwork and fees.

You should also consider how you intend to insulate the new flat roof deck for the roof terrace. May I suggest that you take a look at vacuum insulation with a tapered roof insulation over to create a warm deck roof which removes the need to ventilate a cold deck flat roof. The main PIR insulation manufacturers will provide a free u-value calculation for building regulations approval, obviously using their vacuum insulation products. An EPDM can be adhered to the insulation and the finished then the product of your choice fitted onto pedestals.

The balustrade will also need to be considered in this equation and in particular how it is fixed to the roof.

I suggest that a realistic budget for this proposal is £15,000 - £20,000

Best wishes

Andrew
Rachael Kendrick thanked Room-by-Room (UK) Ltd
paintchartpolly
3 years ago
Ive just jumped onto this thread and have read with interest out of curiosity. I love a roof terrace but did wonder how much value would be added to the property? Would they claw back their investment? I appreciate it's probably going to be a home for some years and therefore it's also about pleasure and experience whilst they live there, but I am curious about whether this makes a property more valuable if put on the open market by the amount it costs to do the works?
PRO
Room-by-Room (UK) Ltd
3 years ago
That's a very interesting comment. May I suggest that probably the most reliable source for this would be a local estate agent. If I was looking at similar properties to buy and one had a small private roof terrace but was £20,000 more expensive, I know exactly which one I would buy. What would you do?
paintchartpolly
3 years ago
I would go for the property without the terrace and add my own value. At least I could shop around, get quotes, and chose the exact roof terrace to my taste!
Rachael Kendrick
Original Author
3 years ago
Ha, you're handier than I! I definitely would have paid more for our place if it had any kind of outdoor area.
Harry Mossman
2 years ago
Hi Rachel, this is a great post :)... did you end up doing this, we are in exactly the same situation in SE London, keen to know who you spoke with about it, may be able to share war stories , good/bad contractors.

We have been quoted 1500 just for the architect to draw up plans and get us to a point where we can bring builders in.. anyone know if this is normal?

Best

Harry
daniscp
last year
I would say £1,500 for the architect drawings is actually reasonable based on the quotes I got last year for the same type of works.

Unclear as to the building costs and timeline as well. Budgeting £15k and 1 month at the moment.

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

Rowland

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

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