Extra work and provisional sums: the two lines in a quote that change the price

Extra work: anything that wasn't in the quote

It happens in two ways. You want something extra, such as a socket by the kitchen island, a different tap or an extra light, or your builder runs into something, such as pipes that run differently than expected, a wall that isn't straight or rotten wood behind old panelling. Each item on its own is small, but together they add up, which is why extra work is the best-known reason a renovation ends up costing more than the quote.

Keeping extra work under control

• Agree the price before the work is done, not afterwards on the final invoice.
• Get it in writing. A message or an email with the work and the price is enough to look back on later.
• Keep a list with a date, a description and an amount for each agreement. Then the final bill won't be a shock and you can check it.
• Ask about the time, too. An extra socket is an hour, but a different layout can mean days.

Read what your contract says about extra work before you sign. Many contracts require it to be agreed first, and in some countries the law asks builders to warn you before something costs more. Even so, an agreement in writing is far nicer than arguing afterwards about what was said.

Provisional sums: an amount that can still change

You'll often see provisional sums for things you still have to choose, such as tiles, bathroom fittings and kitchen appliances. Your builder can't price those exactly yet and puts in an amount instead. Choose something more expensive and you pay the difference, choose something cheaper and you get it back.

A worked example

Your quote has a provisional sum for tiles of €1,500. You choose tiles that come to €2,100 in total. You pay €600 extra.

That's fair, but the risk is a provisional sum that's too low. If it's based on the cheapest tiles in the catalogue, the extra cost is already certain the moment you sign, and the quote looks cheaper than it is.

Ask with every quote

• Which provisional sums it contains. Sometimes they're listed separately and sometimes tucked into a line.
• What each amount is based on: which tiles, which toilet, which brand of tap.
• How the difference is settled. Is there a surcharge on top of any overrun, and is an underrun actually paid back?

If you're comparing quotes from different builders, put the provisional sums side by side. A quote with low provisional sums isn't cheaper, just less finished.

Keep it all in one place

The hard part of extra work and provisional sums isn't the sums but keeping track: the agreement about the socket is in a message, the tile price in an email and the quote in a PDF somewhere in your downloads.

In PLOTT you add the estimated cost and what you've actually spent to each task. You see per budget what's still available, and the quotes are kept with your project instead of in your inbox.