There are three ways to add space to a Victorian terrace: infill the side return, extend across the rear, or convert the loft. Which one is right depends less on how much room you want and more on what you want the room to do — and the best extensions are the ones where you can't tell, standing in the finished kitchen, where the old house stops and the new work starts.
This is how we think about extension work, and what to expect if you're considering it.
What the house gives you
Most of the terraces we work on follow the same plan. Two rooms deep at the front, then a narrower back wing — the closet wing — holding the kitchen and, originally, the scullery. Beside that wing runs the side return: a strip of outside space two metres or so wide, put there by the Victorians to get light into the middle room and give access to the outside WC.
The WC is long gone. What's left, in most of these houses, is a narrow kitchen with one window and an alley you use for storing bikes. That geometry is why the side return infill became the standard East London extension: the space is already yours, it does very little, and filling it turns the worst room in the house into the best one.
The side return
Infilling the side return means taking down the wing's side wall, spanning the gap with steel, and building a new outside wall on the boundary line. The kitchen then runs the full width of the house. Done well, it changes how the whole ground floor works — which is why it's usually done together with a new kitchen rather than before one.
Three things decide how the project goes. The steelwork, which carries the back of the house while the wall comes out. The party wall, because the new wall sits on or near the boundary and your neighbour has rights that are dealt with by agreement before anyone lifts a tool. And the drainage, because the side return very often has a shared drain running down it, which means a build-over agreement with Thames Water before the slab goes in. None of this is difficult. All of it takes time, and a quote that hasn't allowed for it is a quote that hasn't understood the job.
On glazing: the fashion is a fully glazed roof, and we'll build one if it's the right call. But a solid, insulated roof with two or three well-placed rooflights usually gives calmer light, a room that's usable in August as well as January, and a ceiling you can actually light in the evening. Every choice intentional, not default.
Rear and wraparound
A rear extension pushes the back of the house into the garden across its full width. A wraparound does both — side return and rear together — and makes the largest room, at the largest cost, with the largest loss of garden.
The question we always put on the table: what does the garden lose? A terrace garden isn't big. Take three metres off it and you may find you've built a beautiful kitchen that looks out at a fence. Sometimes that trade is right. It should be made deliberately, on a drawing, before it's made in brick.
The loft
Lofts solve a different problem — bedrooms and a bathroom rather than living space. A dormer to the rear is usually the workable shape, and the decisive question is the stair: where it lands, and what you lose on the floor below to make it land there. If the stair costs you a bedroom to gain a bedroom, the loft isn't the answer.
Where new meets old
The junction is the work. Anyone can build a box on the back of a house; the craft is in making the box belong to it.
That means brick that matches — reclaimed London stocks or good handmade equivalents, laid in lime mortar where they meet the original walls, not hard cement that the old brick will lose an argument with. It means floor levels that run through without a step you'll curse for twenty years. It means skirting and cornice that continue rather than stop dead at the junction, and new openings with proportions the house would recognise. An extension shouldn't read as an addition. It should read as the house, continued.
It also means respecting what you find when the wall comes out. These houses are consistent, and the surprises are rarely surprises — we've written about what hides behind the walls and it applies doubly when you're removing one.
Planning and paperwork
Many side return and rear extensions fall under permitted development, which means no full planning application. Conservation Areas — and parts of E17 and the surrounding postcodes are covered by them — change the rules, and lofts and wraparounds usually need consent regardless. Then there are party wall agreements with one or both neighbours, and the build-over agreement if drains are involved. We set out separately what needs planning permission on a terrace, and what does not.
We sequence all of this before the start date is set, and the timeline we give you includes it. The timeline given is the timeline kept — which is only possible if the paperwork is done before the skip arrives.
Cost and timeline
A side return infill with a new kitchen, done to the standard we work to, is typically somewhere between £120,000 and £180,000 depending on the glazing, the kitchen itself and the finishes. Wraparounds run beyond that. On site, expect 14–20 weeks for a side return or rear extension, longer for a wraparound.
Those are honest ranges, not a price list — the number for your house comes as a written scope and a fixed price, and the price you sign is the price you pay. Our guide to what a renovation costs in East London sets out the ranges by project type.
When not to extend
Sometimes the room you want is already inside the house. A closet wing knock-through, a moved doorway, a rethought hallway — internal remodelling can give you the kitchen-diner you're picturing without building anything, at a fraction of the cost and disruption. If that's true of your house, we'll say so at the first consultation. Saying no to the wrong project early is the only way of saying yes to the right one properly — and that applies to projects we'd otherwise be paid to build.