What is a bill of quantities?

How it works in Ireland

A bill of quantities breaks a build into items such as excavation, blockwork, roofing and electrics, each with a measured quantity. Builders put a rate against every line, so you can compare tenders item by item instead of comparing one lump sum with another.

Not every project uses one. The RIAI standard forms include a contract designed to be used without quantities, where there is no itemised bill. In that case the price rests on drawings and a specification, which makes it more important that those are complete.

On the money side, a lender’s self-build conditions can include a quantity surveyor’s costings that show the full cost of the build. Check what your own lender asks for, since the requirement and its format depend on the product.

What to ask

Ask your architect whether the project needs a bill of quantities or whether drawings and a specification are enough. If a quantity surveyor is involved, ask what they will produce, what it costs and whether it can feed your stage payments. Ask each builder how provisional sums and allowances are handled, since these are the lines most likely to change the final price.

Make sure every tenderer prices the same documents. Otherwise a cheap tender may only reflect something left out.

A common mistake

Comparing tenders with different scopes. Three prices are only comparable if each builder has priced the same items. A bill of quantities is one way to make sure they have, and a written scope with clear allowances is another.

Keep the final bill with your build records. If a variation or a dispute comes up later, an itemised list of what was priced is far easier to argue from than a single lump sum, and your lender or quantity surveyor may want to see it when checking a stage payment against the work done.