So it was no surprise that Forster, 34, and his partner, interior designer Paul Longman, wanted to put their stamp on their Rotherhithe flat by creating an additional floor. When they bought the sixth-floor home in a Nineties block in 2011 it was laid out on one floor, but had a timbered loft space big enough to make habitable. The flat as it stood was dull, dingy, divided and dated. Forster said it looked like a cheap rental.
"We got a few quotes, some were ridiculously expensive, some wouldn't even look because it was so high up," says Forster. But the quote submitted by surveyor Rob Woods won the couple's approval.
After lengthy discussions, Forster and Longman added two bedrooms with en suite bathrooms, plus a small veranda with a glass floor, through which you can see down into the flat. By moving the bedrooms upstairs, the floor below became one large livingdining room. Lots of skylights make the whole space very bright.
"Planners will want you to leave the existing roof," advises Woods. "This job took 12 weeks as it was a large loft, and we had to use scaffolding and a winch. A simple loft conversion might take eight weeks."
The verdict: "Rob and his team were open to all our suggestions and from day one it was so smooth," says Longman. "It has added a lot of light and space. We're so happy with it."
What it cost:
Flat in 2011: £367,000
Total spent including decorating: £130,000
Value now: £950,000
Loft conversion by Simply Loft at www.simplyloft.co.uk
Simply Loft's prices range from about £30,000 plus VAT for a small loft conversion to £90,000 plus VAT for a large one.
Will you need planning permission?
Whether you enlarge your home upwards, out at the back, sideways — or all three — above-ground extensions are the best and cheapest way to improve, bringing light, space, plus the unquantifiable aspect of joy into your life.
If you own a house that isn't in a conservation area, or listed, you can do some of these things without planning permission. Existing permitted development rights mean you can add a certain amount of extra space without it. These rights have been extended in the past few years so that larger extensions can be built without planning consent.
As architect Neil Dusheiko says, when you are building up to the party walls of a neighbour's property, you will also need party wall agreements. For this, you appoint a party wall surveyor and will likely have to pay for an independent one for your neighbour, too. "These surveyors are impartial," says Dusheiko.
"Their concern is looking after the wall. It is a very sound system."
In the case of lofts, if you own your house — again not listed and not in a conservation area — you will likely be able to extend up into the space, including putting dormers of a certain size at the back, without planning permission. However, for a flat, you will need those permissions.
You can't put dormers at the front without permission, and there are rules about how much volume you can add. Verandas and terraces always need permission, wherever they are.
This is a brief snapshot, but there is a really useful guide here.
Don't forget, you can always have a chat with local council planners, who are happy to give advice at the start of any project. Either ask them yourself, or your architect can do it for you.