Price per m² vs fixed price for demolition: which suits your job?

What is the difference between a per m² price and a fixed price?

With a unit price, the quote states a rate per square metre (or per linear metre, per cubic metre, per load) and the final amount is the rate multiplied by the quantity actually executed and measured. With a fixed price (precio cerrado), the quote states one amount for a defined scope, and that amount stays the same unless the scope changes.

The difference is not only how the figure is written. It decides who carries the risk of quantities being larger than expected. Under unit rates, the owner pays for more metres if there are more; under a fixed price, the contractor absorbs it, as long as the extra work was within the described scope.

A side-by-side comparison

Neither column is free of friction. Unit prices shift the argument to measurement; fixed prices shift it to scope. Whichever you choose, the quality of the written description decides how smooth the job is.

When does a per m² price make sense?

Unit rates are the honest choice when the quantity is genuinely unknown or repetitive. Typical cases:

• Slabs and paving across a large plot where the area is known but the thickness and reinforcement vary.
• Interior strip-outs of floor and wall tiles, where the area is measurable but layers may be doubled under the visible finish; see interior demolition cost.
• Foundations that only become visible once the structure is down.
• Industrial floors and yards, often priced by area or volume of concrete; see industrial demolition cost.

The condition is an agreed measurement method: how and when the quantity is measured, who confirms it and how it is documented. From abroad, photos with a measuring tape or a short video of the uncovered element are a practical way to verify it.

When does a fixed price protect you better?

A fixed price works best when the whole scope can be seen and described before the machine arrives. A villa above ground with a known roof type, an outbuilding, a pool whose dimensions are on the plans, or a defined list of interior walls are good examples.

For an owner managing the project from another country, the main advantage is predictability: the budget is known, stage payments can be tied to visible milestones, and there is no need to supervise measurements. The price of that certainty is that the contractor builds a margin for normal variations into the figure, and that anything outside the written scope becomes a variation that has to be agreed. The guide stage payments and written contracts for demolition explains how to tie those payments to milestones.

The hybrid quote: fixed where it's known, unit rates where it isn't

Most of our quotes for whole properties use a hybrid structure, because most properties mix a visible part and an invisible one. The house above ground, the roof, the pool and the outbuildings are priced as a fixed amount; foundations, buried tanks or slab areas that cannot be measured beforehand are priced at a stated unit rate, with an estimated quantity for budgeting.

This gives you a firm figure for most of the work and a transparent rule for the rest. It avoids two bad outcomes: a fixed price inflated to cover worst-case foundations, and an open unit-rate contract where the total is unknown until the last day. The page demolition cost per m² shows how unit figures are built, and the house demolition cost page explains which parts of a house are usually fixed.

What about prices per load, per cubic metre or per day?

Square metres are not the only unit used in demolition. Depending on the work, a quote may use other units, each with its own logic:

• Per load or per skip for rubble removal, where the quantity is easier to count in trips than to measure in place.
• Per cubic metre for solid concrete elements, such as foundations, thick slabs or retaining walls, where thickness matters more than area.
• Per linear metre for walls and boundary fences of a fairly constant height.
• Per day of machine and crew, occasionally, for work whose scope cannot be defined at all in advance; this gives the owner the least certainty and should be the exception.

Whatever the unit, the same rule applies: it has to be clear what one unit includes, how many units are expected and how the final count is confirmed. A unit nobody can verify is not a price, it is an invitation to argue.

How to read either type of quote without getting caught out

Whichever model you are offered, a few questions reveal whether it is well written:

• For unit prices: what is the unit, how is it measured, at which stage, and what is the estimated quantity for budgeting?
• For fixed prices: what exactly is included, what is excluded, and how are variations priced if the scope changes?
• For both: is waste handling included in the rate or the fixed amount, and do you receive the delivery receipts?
• For both: is VAT shown separately, and which rate applies?

If one quote is per m² and another is fixed, convert them to the same basis before comparing: multiply the unit rate by a realistic quantity, and check whether the fixed price covers the same scope. Our demolition quote comparison checklist helps with that, and the quote request lets you ask for either structure. For slabs and foundations specifically, our sister site explains the technical side of slab and foundation demolition.