Wrap Around Extensions

What it does to a terraced or semi detached ground floor

The old plan disappears entirely, which is the point and also the risk.

A standard terrace ground floor is a front room, a middle room, and a kitchen in the outrigger, connected by a hall and a series of doorways. Every room has one function and one window, and the whole arrangement was designed around a scullery and a coal fire.

A wrap around typically removes the outrigger side wall along its full length and the rear wall of the main house, so the middle room, the old kitchen and both new elements become one continuous space. You end up with a room that might be 6 metres wide and 7 metres deep, with the stairs and the front room still separate.

The gain is obvious. The risk is that a large open room with no structure to it is not automatically a good room. Three things need deciding at drawing stage rather than on site: where the noise from the kitchen ends and the sitting area begins, where the daylight comes from in the middle of a plan that is now deep, and whether the front of the house still has a door you can shut when someone wants quiet.

The layouts that work usually keep something. A part height wall, a change in ceiling level, a structural post left visible rather than boxed, or a step in the plan where the L turns. Rooms that are entirely undifferentiated tend to be used less than the drawings suggest.

The eight week determination, and what happens inside it

Eight weeks from validation, and validation is not the day you press send.

A householder planning application has a statutory determination period of eight weeks from the date the council validates it. Validation means the submission is complete: correct drawings at correct scales, a location plan, a site plan, the right fee and the right forms. An incomplete submission sits in a queue until it is fixed, and that time is yours, not the council’s.

Inside the eight weeks the application is publicised, neighbours are consulted, and a case officer assesses it against the local plan and national policy. On a wrap around the questions asked are usually the same ones: impact on the neighbouring property’s daylight and outlook, whether the depth alongside a shared boundary is overbearing, and whether the design sits comfortably with the existing house and the street.

Officers frequently apply a rule of thumb about how far an extension may project alongside a boundary before it is considered overbearing, judged from the neighbour’s window positions. That is where a wrap around gets tested hardest, because the side element runs along the boundary for its whole length.

Nobody can promise you an outcome, and anyone who does is selling something. What can be done is to design with the objections in mind: setting the depth back from the boundary at the far end, keeping the eaves low next door, and showing the daylight position honestly rather than hoping it is not noticed.

Two boundaries at once, and the Party Wall Act

A wrap around usually engages the Act on more than one section and against more than one neighbour.

The Party Wall etc. Act 1996 is not planning and it is not Building Regulations. It is a separate statutory process between you and your neighbours, and on a wrap around it is a certainty rather than a possibility.

Section 1 covers building on the line of junction, which is what you do when the side return goes right up to the boundary. Notice is one month.

Section 2 covers work to an existing party wall or party structure: cutting into it, raising it, taking bearing off it, cutting away projections. Notice is two months.

Section 6 covers excavation within three metres of a neighbouring structure to a depth below their foundations, and within six metres where a deeper foundation cuts a notional line drawn at 45 degrees from theirs. On Victorian terraces with shallow footings and a modern foundation at 900mm or more, section 6 is triggered almost every time. Notice is one month.

The wrap around difficulty is that the side element engages the boundary on one side while the rear element frequently engages a different neighbour on the other, or the rear boundary. Two neighbours, potentially three notices, and the periods run from service, not from when you would like to start.

Temporary support, in a space with no room in it

The riskiest days on the job, on the most confined site of any extension type.

While the two walls are out and before the frame is in, the house above is held up by needles and props. On a rear extension that happens on one line with a garden behind you and space to work. On a wrap around it happens on two lines at once, meeting at a corner, inside a side return that might be 1.8 metres wide, with the neighbour’s wall a hand’s width away.

The propping is designed rather than improvised: where the needles go, what they bear on at both ends, how the loads are shared, and what order the walls come out in. Props stood on a suspended floor that was never designed to take a point load do not do what they appear to be doing.

Sequencing matters more here than anywhere. In practice the pads go in first, then one line is propped and its beam installed and pinned up before the second line is touched. Doing both at once to save a week is where structures come down.

This is the phase where cutting corners does not produce a crack two summers later. It produces a collapse on the day.

Drainage, which is always exactly where you want to build

The side return is where the Victorian drainage runs. All of it.

On a terrace the soil stack, the gully, the rainwater downpipe and frequently a drain serving several houses all run down the side return, because that is where they were put in 1890 and nobody has moved them since. A wrap around builds over that entire run and then builds over the ground beyond it too.

A drain serving more than one property is a public sewer for these purposes, even where it sits entirely inside your garden. Building over it, or within three metres of it, requires a build over agreement from Anglian Water. That is a separate application on its own timescale, and it can require a CCTV survey of the run, a foundation designed to bridge the drain rather than load it, a change of position, or a diversion.

Inspection chambers cannot simply be built over and forgotten. Where a manhole falls inside the new footprint it is either relocated, which needs the water authority’s agreement where the run is public, or fitted with a sealed double sealed cover with access maintained and the chamber upgraded to suit being inside a building.

Surface water is the other half. A wrap around adds a large roof area and usually a new patio at the same time, and the run off has to go somewhere. Soakaways in clay perform poorly and need testing rather than assuming. On a terrace with no room for a soakaway the answer is usually a connection into the existing surface water system, which needs to be found and proved first.

We lift the covers and follow the falls at survey stage. It takes twenty minutes and it is the cheapest twenty minutes on the job.

The dark middle room, and designing it out

The most common regret, and it is entirely avoidable at drawing stage.

A wrap around covers the ground on two sides of the house. Any existing room that had a window onto the side return or onto the part of the garden now built over loses its daylight. On a terrace that is usually the middle room, which was already the darkest room in the house.

If the middle room is being absorbed into the new open plan space, that can be fine, provided the rooflights over the old wall line are there to replace what was lost. If it is staying as a separate room, a snug or a study or a downstairs bedroom, then it needs a source of light of its own and there are only three answers: a light well or open court left in the plan, a set back so part of the old wall stays external, or roof glazing over a section of the new roof that sits above it.

All three cost floor area or money. All three are cheap compared with living with a room nobody uses. This gets decided on the drawing, because after the roof is on there is no answer at all short of taking part of it off again.

Insulation, thermal bridging and how the room will feel

A cold extension is a room nobody uses, and it is entirely a specification decision.

Part L sets minimum values for the new walls, floor and roof, and current minimums are considerably better than the house you are attaching to. That produces an effect people do not expect: the new space is the warmest part of the house and the old rooms feel worse by comparison.

The floor is where corners get cut, because nobody sees it. Insulation under a ground bearing slab is cheap at the time and impossible to add afterwards without taking the floor up. Get the thickness right at specification stage.

Thermal bridging decides whether the extension performs the way the calculation says it will. The junctions that matter are wall to floor, around every opening, at the eaves, and on this job specifically around the steel frame. A steel post or beam passing from inside to outside is a direct path for heat and a guaranteed cold spot where condensation and then mould will appear. Steels get wrapped and the insulation line gets carried continuously past them. Insulated cavity closers around every opening, insulation carried down past the slab edge, continuity at the roof junction.

Heating is a design question rather than an afterthought. Adding 35 square metres of heated space means the existing boiler is serving a considerably larger load, which is worth checking rather than assuming on an older system. Underfloor heating suits an extension because the floor is being built from scratch anyway, and it pairs sensibly with a large glazed area where a radiator would have nowhere to go. If it is going in, it is decided before the slab, not after.

What a wrap around extension costs

The highest rate per square metre of the single storey types, for reasons that have little to do with the building.

Costs move with materials, labour and specification, so treat this as indicative at the review date at the foot of this page rather than as a quotation.

As a broad guide, a wrap around typically runs £2,600 to £3,500 per square metre for the shell and a standard finish. On a 32 square metre wrap around that is roughly £83,000 to £112,000 before the exclusions below. Difficult access, deep or piled foundations, wide structural spans, extensive glazing or a high specification push toward and past the upper end, and there is no ceiling on the last of those.

That range normally includes:

Two of the exclusions deserve a number rather than a mention. Party wall surveyor fees on a wrap around, where two neighbours are notified and at least one dissents, are real money and they are payable by you as the building owner. A build over agreement carries an application fee and often the cost of a CCTV survey. Neither is a reason to avoid the work. Both are a reason to know the figure before you commit rather than after.

The variables that move the total most, in order, are foundation depth, access, structural span at the corner, glazing specification and roof form. An identical extension on a mid terrace where everything comes through the hallway costs meaningfully more than one on a semi with a driveway, and that has nothing to do with the extension itself.

Which Colchester housing suits a wrap around

The stock that has a return to fill sits in specific parts of the city, and some of it is designated.

The classic candidate is the Victorian and Edwardian terrace with a rear outrigger and a narrow strip beside it. In Colchester that stock is concentrated in New Town and the streets running off Military Road and Magdalen Street, the roads off Maldon Road, and the pockets around Barrack Street and the station. Those houses are long and thin, and a wrap around is the only move that makes them wide and deep at once.

Interwar semi detached housing across the city has a different opportunity: a side passage or driveway rather than a return, and usually a rear projection of some kind. A wrap around there is more likely to be achievable within a sensible envelope, but building across the passage removes garden access permanently unless a route through the extension is designed in.

The Dutch Quarter and the historic core are a different exercise entirely. The property is older, often timber framed, frequently listed, and almost all within a conservation area. It is doable and it takes longer, with listed building consent as a separate decision. Lexden has substantial period property with generous plots, and much of it is designated too.

Wivenhoe has good terraced stock near the waterfront inside a conservation area. Brightlingsea and parts of Manningtree are similar. The villages north and west of the city, West Bergholt, Fordham, Dedham and the Colne valley, have a mix of period cottages, many of them in designated areas, and postwar housing where the rules are more straightforward. A bungalow wraps around more easily than any of them, with no first floor to build under.

On estate housing from the 1960s onward there is frequently no return to fill, because those plans were already square. If what you have is side access rather than a side return, the equivalent move is a rear plus side extension, which is the same construction with a more forgiving site.

How we do it

One contract, one contact, and the paperwork is our problem rather than yours.

Our team has 25+ years in the trade and comes out. On a wrap around the survey looks hard at five things: what the boundary walls are founded on, where every drain runs and who else uses it, what is above the two walls coming out, whether there is a tree within influencing distance, and how material will physically reach the back of the house.

Most people who call us already have drawings and permission and want a builder to price the work and build it. That is the ordinary job here, and we are glad to work to somebody else’s plans. Where the drawings do not exist yet, we bring in the technician who draws it and the structural engineer who calculates the frame and the foundations. We handle the party wall notices, manage the planning route, deal with Anglian Water where a build over agreement is needed, and notify Colchester City Council Building Control. We work as main contractor, so the trades answer to us and we answer to you.

Probuild Extensions Colchester is the extensions arm of Essex Probuild Ltd, company number 15979928. We carry £2m public liability cover, and everything is built to current Building Regulations. We notify Building Control, arrange the inspections and see the job through to the point where they issue your completion certificate. Our rating on Google is 4.6 from 10 reviews.

We are based in West Bergholt, about three miles north west of Colchester, and work across the city and roughly thirty miles around. The survey and the quotation cost nothing and there is no pressure afterwards.