Clients often ask me how much their proposed building or extension is going to cost them. This is never an easy question to answer, if indeed an Architect should answer it at all. Strictly speaking, I am not qualified to give detailed cost advice to people, for that you need a Quantity Surveyor. I can tell you that, from experience, house extensions around Edinburgh tend to costs between £1000 and £1500 per square meter. A builder whom I regularly work with tells me his extensions work out around £1200 per square meter. This changes over time and I keep an updated guide to the cost of typical house extensions on my website. While these figures are useful, remember they are based on a number of assumptions:1. The building is "typical", that is its one or two storeys, timber frame, masonry external walls (rendered or exposed brick) with a slate or tile roof. As my builder friend told me recently, "it costs more for Architectural extras", by which I think he meant large areas of glass, timber cladding and metal roofs.2. The site is conveniently located, not in the middle of nowhere or on the side of mountain (sloped sites are tricky to build on). City centre sites also pose challenges. The ideal site, from a builders perspective, is semi-rural or suburban.3. If its an extension or internal alteration, is the building listed or in a conservation area? if so it can cost more as specialist trades and materials may need to be used, like real lead and slate, lath and plaster, cut stone etc.
People appreciate being given something like a rule of thumb to work with but they often need more. I have two clients at present who want to conduct a preliminary tender process based only on planning drawings, something unheard of a few years ago. In normal economic conditions, a builder will engage in a tender process if they think they stand a realistic chance of getting the job. Tendering on planning drawings means there isn't any detailed construction information, this usually comes during the Building Warrant phase. There is also the risk of time delay, the builder knows that if we only have Planning drawings then we still need to go through the Building warrant process and that could take 2-4 months for a house extension. In that time, building material prices and labour costs may increase and his original tender estimate will be under-priced.
Despite these risks, I am having no trouble finding builders who want to bid for these projects.
The only thing left to worry about then, is my fee.