Renovation Cost Overruns & Scope Creep

Usually because they cover different things. One may include hacking and disposal, another may not; one may allow for waterproofing, another assumes the existing is sound; material allowances differ. This is why comparing headline totals is misleading. Ask each contractor for an itemised breakdown and compare the scopes rather than the numbers.

We will not publish a percentage, because it depends entirely on the property's age and how much of the work is behind walls and floors — a figure quoted here would be a guess dressed as advice. What we can say is that the older the property and the more hidden work involved, the more sense a contingency makes, and your quotation discussion is the right place to size it.

A variation is any agreed change to the original scope — an addition, a substitution or something discovered on site. They are a normal part of renovation and not in themselves a warning sign. What matters is the process: a variation should be described, priced and agreed before the work is done, not presented afterwards.

For work that is fully visible and well defined, a quotation can be very close to the final figure. Where the job involves opening up walls or floors, an honest answer is that the quotation covers known conditions and that anything found will be priced as a variation. Any contractor promising a fixed, unchangeable final figure for concealed work is making a promise they cannot see well enough to keep.

It is worth understanding why before deciding. Sometimes there is a legitimate reason. More often the low quotation has excluded something the others included — hacking, disposal, waterproofing, making good — which reappears later as an extra. Read the exclusions rather than the total.