Send a set of drawings out for an estimate and you'll get back very different things depending on who measured it. Some come back as a single lump sum with no way to check it. Others come back broken down so you can see exactly where every pound sits. Only one of those is any use once you're on site.
So before you pay for one, or rely on one to price a tender, it helps to know what a building estimate should include. Not the presentation. The substance: what's measured, how it's priced and what's written down about the bits that couldn't be priced yet.
A number without a breakdown is just a guess with confidence
If an estimate can't show you labour, materials, preliminaries and overheads as separate lines, you've got no way to check it against your own pricing or push back on a figure that looks wrong. A total on its own might be right. You just can't tell.
A proper estimate breaks down against NRM2 so every line is traceable. That matters for three reasons. You can check it against the drawings. You can compare it with your own figures or a subcontractor's quote, item by item. And when something changes later, you can see exactly which lines it touches.
A lump sum gives you none of that. It's a number you have to take on trust, and trust isn't much use in a variation dispute.
What a building estimate should include, line by line
Whoever prepares it, a usable estimate should give you all of the following. If something's missing, ask for it before you rely on the figure.
- A list of drawings and revisions. Exactly which sheets were measured, so you know whether it matches the current set.
- Measured quantities. Every item with a quantity and a unit, organised by element, measured to NRM2.
- Rates you can see. A rate against each quantity, not just an element total.
- Labour, materials and plant split out. So you can tell where the money and the risk sit.
- Preliminaries priced separately. Site set-up, welfare, supervision and access, tied to a stated programme.
- Allowances labelled as allowances. Anything not yet designed, with a clear note of what it's for.
- Assumptions and exclusions. What was assumed where the drawings were silent, and what isn't priced at all.
That list is also a quick way to compare two estimates side by side. If one has all seven and the other has two, you already know which is worth more, whatever the totals say. For a closer look at the contents, what's actually in a proper cost estimate goes further.
If you can't check an estimate, you can't defend it. The breakdown is the part you're really paying for.
The drawings and specification decide the accuracy
An estimate built from a full set of drawings and a proper specification will always be tighter than one built from a rough sketch and a phone call. If the information going in is thin, the number coming out will be too, no matter how it's presented.
So send everything. Plans, elevations, sections, details, structural drawings, the specification, any surveys. If a document doesn't exist yet, say so, and expect it to show up in the estimate as an allowance or an exclusion. That's not the estimator being awkward. It's them being honest about what can and can't be measured.
Be wary of an estimate that comes back from thin information with no allowances and no exclusions at all. Either someone's made a lot of silent assumptions, or they haven't looked closely enough to notice what's missing.
Preliminary and detailed estimates serve different stages
Early in a job, before drawings are finished, a preliminary figure gives you a working number to plan around. It'll lean on allowances and broad element figures, and that's fine, as long as it says so.
Once drawings are locked down, a detailed estimate measured line by line replaces it. Knowing which one you're asking for, and which one you're being given, matters. A preliminary figure treated as a tender price is how people end up committed to a number that was never meant to carry that weight.
If you're not sure which you need, ask yourself what you'll do with it. Deciding whether a project is viable? A preliminary figure may do. Submitting a price you'll be held to? You need the detailed one.
It should stand up at tender and on site
A good estimate isn't just useful for pricing the job once. It should give you a structure you can keep referring back to when a variation comes in, when a client questions a cost, or when you're checking your own numbers against what was originally measured.
Speed matters as well, but not at the cost of accuracy. A quick estimate that's wrong costs you more than a slower one you can rely on. What you want is a measured breakdown back in time for your deadline, agreed at the start, rather than speed for its own sake.
The five-line test
When an estimate lands, pick five lines at random. For each one, can you find the drawing it came from, see how the quantity was worked out and understand the rate? If you can, the estimate will hold up. If you can't find the answer for even one or two, you're looking at a guess dressed as a breakdown. That, in the end, is what a building estimate should include: enough detail that any line can be checked by someone who wasn't there when it was priced.
Our construction estimating services measure every element from your drawings to NRM2, price it on current rates local to the job and set out the assumptions plainly. You can see the format in the sample estimate before sending anything.