Extensions and annexes to your house in Nieuwegein

For most people an extension is the cheapest way to get more room without moving house. You put a piece onto the house and the kitchen, the living room or the utility room gets exactly as much bigger as you build on. What people misjudge is rarely the extension itself. It is everything around it: the foundation that has to go into the ground, the hole that ends up in a load-bearing wall, and the room that turns out to need laying out again afterwards. I build on site, from the groundwork to the last skirting board, and across that whole run you deal with one person.

Annexe or extension, what is the difference

In conversation the two words get used interchangeably and usually I do not correct that, because the plan is the same: more floor area. For the work it does matter.

With an extension you enlarge a room that is already there. The back wall gets opened up, the new space becomes part of the room that was there, and you walk into it without a step. With an annexe you put a space against the house that stays its own. Its own roof, often its own door, sometimes its own use such as a store, a study or a utility room. The existing wall can then largely stay standing.

That difference lands straight in the budget. With an extension you take out a piece of load-bearing wall, and then a steel beam nearly always goes in to take over what that wall was carrying. With an annexe that stays closed, it does not have to. It is the clearest example of a choice that looks small on paper and is large in the cost.

Back, side or front

An extension at the back of the house

Extending happens most often at the back, and with reason. The back wall is the wall the streetscape notices nothing of, the garden gives room to work, and the rooms that sit against it are exactly the rooms people find too small.

Two things I point out beforehand. The garden gets smaller, and that sounds obvious until you are standing there with a tape measure. And the deeper the extension, the darker the old middle of the room becomes, because the daylight that used to come in through the back wall now has further to travel. That can be solved, but it is a design question and not a detail for afterwards.

Access counts for more here than people think. If there is a side gate that sand, concrete and window frames can come through, the work runs smoothly. If everything has to go through the house, or over the roof with a crane, the same work costs more time and more protecting of what is already there.

An extension at the side of the house

At the side it works if there is ground beside the house, so on an end-terrace, a semi-detached or a detached house. Here the boundary line and the building envelope lead, and those two are not up for negotiation.

The building difference with the back sits in the roof. A side extension often ties into an existing sloping roof surface rather than onto a straight wall, and that junction is the point where leaks start if the work is done sloppily. On top of that a side wall is usually visible from the street, so the outside finish counts here for looks as well, and that runs through the facade cladding.

An extension at the front of the house

Extending at the front of a house is the rarest version and the most regulated. The front elevation sets the streetscape, so councils look harder at it, and the front garden is often too shallow for a proper room. In practice it therefore usually ends up not as a full-width extension but as a shallower widening of the hall or the entrance, or a bay window.

I would rather say up front that there is a chance of objection than have you find out during the application. If it gets stuck with the council, the answer is nearly always that the same square metres are fine at the back.

An extension for the kitchen or for the living room

The kitchen in the extension

This is one of the most common reasons to build. The kitchen shifts into the new space, and where it stood a dining table or a seating area comes. In building terms it means the pipework has to come along. Water, waste, electrics, and with an island those connections run through the floor.

That is why I want to know the kitchen layout before the floor is closed up. A waste pipe has to run on a fall and that fall has to come from somewhere, so the height of the floor build-up hangs off where the sink goes. Anyone who works that out after the pour ends up hacking it back out later. If there is going to be a floor running through from old to new, the flatness of the existing floor matters just as much as that of the new one, and that falls under flooring and tiling.

Extending the living room

With a living room extension nearly everything turns on light and on glass. The more glass in the new back wall, the more the extension feels like the garden carried on rather than a box stuck on the end. At the same time glass is the part that pushes the price up fastest, and a wide set of sliding doors asks for a heavier lintel and a foundation that carries it.

If you want to bring the daylight in from above instead of only from behind, you end up at a skylight or a glass extension. That is a story of its own with choices of its own, and it sits on the page about sunrooms and skylights.

A timber annexe

A timber annexe is built up as a timber frame instead of as brickwork. It is lighter, which means the foundation sometimes does not have to be as heavy, it insulates well with a relatively thin wall build-up, and it stands weathertight sooner.

The honest downside sits on the outside. A timber extension or annexe stands or falls on the detailing around the junctions and on the facade finish. Where timber stays wet for long and cannot dry, it goes, and that is not a fault in the material but a fault in the building. Ventilation behind the boarding, the right overhang and a well thought out roof edge profile do more for the lifespan there than any brand of stain. If you want to really see that timber look, wood facade cladding belongs with it, along with the maintenance that comes with it.

Prefab or built on site

A prefab extension is made in the factory and set on site. That goes fast and it is a decent product, but it starts from fixed sizes and from a wall that stands straight. Existing houses rarely are. Walls lean, floors are not level and the existing foundation is not always where you expect it.

So I build on site. I measure the wall as it actually stands, and the new structure follows that dimension instead of the other way around. That costs a bit more time in the build, and it saves the kind of filler pieces and lines of sealant you keep looking at afterwards. If the work runs further than the extension alone, for instance because the whole ground floor gets laid out again, that falls under a complete renovation and I plan it as one job.

What makes an extension dearer or cheaper

How much an extension costs hangs off a handful of choices.

The foundation

Everything starts under the ground, and that is straight away the item with the most uncertainty. How much load the ground carries, how deep the foundation has to go and how the new foundation joins the existing one are three questions you only fully know the answer to once the ground is open. Where the subsoil is soft, this becomes the heaviest part of the budget, even though you will see nothing of it afterwards.

The roof

A flat roof is simpler and therefore kinder than a roof that gets tied into the existing one. If a skylight goes in it, that brings not only the glazing but also the structure around it and the detailing that keeps it watertight. The rainwater run-off is a choice as well, because the water that used to fall on your garden now falls on a roof and has to go somewhere. The roofing itself is a trade of its own, and you will find that at roofing and roof renovation.

How much glass goes in

A wall with a wide set of sliding doors is a different wall from one with a door and two windows. More glass means a heavier lintel, more weight on the foundation and dearer glazing. It is also the choice you steer the look with the most, so this is the item where shifting the budget pays off most.

Whether the kitchen moves with it

If the kitchen stays where it is, the extension is shell plus finish. If it moves along, pipework, waste, electrics and ventilation come with it, plus work in the existing house to get those services to their new spot. That is not a small extra.

Whether a steel beam has to go in

As soon as the wall being opened up is carrying load, a steel beam goes in. That means a structural engineer doing the calculation, steel ordered to size, and a moment when that steel has to get inside. If there is no side access, a beam goes through the house or over the roof with a crane, and that is a day with a completely different character from the days before it. I plan that up front and tell you in good time what it asks of you.

Why a price per square metre says little

A figure per square metre is a handy sum and a poor way to compare extensions. The dearest parts do not scale with the floor area. A foundation, an opening with a beam, a set of sliding doors and the junction with the existing house cost roughly the same whether you put up a modest or a generous extension. Spread those fixed items over few square metres and the price per metre comes out high.

How it goes

You send me a message with what you want and a few photos of the wall and the room behind it. I usually reply the same day and come and look. On that visit I measure up, look at the structure and walk you through the choices that do the most to the price. After that you get a quote per item, with the uncertainties named honestly rather than tucked out of sight.

I work out of Nieuwegein and for this work I come to the surrounding towns too, such as Utrecht. I am not a building firm with a planner and a site manager, so I can only stand in one place at a time. The advantage of that is that on an extension, where groundwork, brickwork, carpentry, roof and finishing touch each other daily, you never have to work out who promised what.