The questions everyone asks

It depends on five things: the depth and width, what the foundation demands, how much glass goes in, whether a roof light and underfloor heating are included, and whether you want a shell or a finished room. We do not put a figure on the site because a price without your address attached is worth nothing. But we do explain exactly where the money goes, and after one visit you get a price per element.

Per square metre, usually more than a ground-floor extension, because you are building on top of an existing house. The biggest variable is the existing structure: can the foundation carry the extra floor without work below, or not? That is also why the first visit matters more on a roof extension than on any other project.

On site, usually eight to twelve weeks, depending on size and level of finish. Preparation comes before that: design, structural calculations and, where needed, the permit procedure. That procedure usually takes the longest and it sits with the council, not with us.

Ten to fourteen weeks on site to move-in ready. The tense part (roof off, elements on, wind- and watertight) is often done within a week, because we work with prefabricated timber frame elements. The rest of the time goes into services, the staircase, the bathroom and the finish.

In most cases yes, in one of the two directions. What decides it is your house type, the foundation, the space on the plot and what the zoning plan allows. For an apartment, the owners’ association also has to agree. We check that for your address, and if the answer is no, you hear it from us before a euro has been spent.

Sometimes not, often yes. It depends on the depth, the height, the position on the plot and on your municipality’s zoning plan; in a protected townscape, extra rules apply. We look it up for your address and can handle the application. What we do not do is promise in advance that you need no permit or that one will be granted. That judgement belongs to the council.

Yes, and in an extension it is nearly always the sensible choice: a lot of glass and little wall for radiators. We build it into the floor construction and connect to your existing system. If your current boiler cannot carry it, that change is in the quote rather than turning up later as extra work.

Almost always. The question is more which: two, three or four panels, aluminium or uPVC, with a standard or a recessed threshold. That last one (doors you walk through with no step) has to be prepared in the shell, so it is a decision for the start and not for halfway through.

Yes, and it is one of the most requested elements. It does require the pipework, drainage and ventilation to be right from the first drawing. A bathroom squeezed in later becomes expensive and is rarely elegant. So mention it in the first conversation, even if you are still unsure.

Yes, and that is our standard: plastered, painted, floor laid, lighting connected, staircase fitted and the bathroom working. You can also choose wind- and watertight and do the rest yourself. The quote then states exactly where our responsibility ends.

With an extension, the rear wall usually comes out (partly) and a steel beam carries what sits above it. With a roof extension, a light timber frame structure goes on top of the existing walls. In both cases a structural engineer calculates what the existing foundation and walls can take. That calculation is not a formality, and you receive it with the paperwork.

You send a request or call. We reply within one business day and arrange a visit of about an hour. After that you receive, within five to ten business days, a quote built up per element, including what is not in it. If you want to leave something out or add something, you adjust it and see immediately what that does to the total.

Honestly: for a number of weeks, quite a lot. There is a skip, there is dust and there are people in the house. What we do about it: seal off the work area against dust, tidy up daily, give you a schedule per phase in advance, and keep the heaviest days (breaking through, or taking the roof off) short and agreed with you.