Medir un bill of quantities según ASMM 6

Write the basis down first: that the bill is measured to the Australian Standard Method of Measurement of Building Works, sixth edition, which departures from it the job needs and why, what the rates are deemed to include, and what the bill does not cover. Record the drawing revisions the measurement is being taken from in the same place.

Por que: The preambles are the part of the bill that is read only when there is a dispute, which is exactly why they have to be written when there is not. A tenderer who priced a rate on the assumption it excluded something the measurer assumed it included has not made an arithmetic mistake, and no amount of levelling afterwards recovers the difference.

Open the drawings on the measurement canvas, calibrate the scale against a figured dimension rather than a printed scale bar, and take the areas in square metres, the lengths in metres and the counts each trade section needs. Every measurement keeps the sheet number and the revision it came off.

Por que: A drawing is reissued on every live job, and the only measurements that survive a reissue are the ones you can find again. A quantity with no sheet behind it cannot be rechecked, so it has to be re-taken from scratch, and the second take-off never agrees with the first.

Set the waste allowance for each material on its own register, so the bill quantity stays the net quantity of finished work the standard asks for and the cutting, laps, returns and breakage are priced where they belong. Reinforcement laps, tile cutting and plasterboard offcuts all live here rather than in the measured area.

Por que: A quantity quietly grossed up for waste reads as a measurement and behaves as a rate, and nobody downstream can tell which it is. It also breaks the one thing a bill is for, because the next valuation measures the finished work on site and finds less of it than the bill said there would be.

Write each item with the description, the unit and the quantity the standard calls for, and group the items into the trade sections it organises the work by. Price them from the cost database or from your own rates. An Australian bill is measured by trade, and the elemental view of the same money is produced alongside it rather than instead of it.

Por que: The description is the contract between the measurer and the estimator. An item written loosely gets priced six different ways by six tenderers, and the levelling that follows is an argument about your own words rather than about their offers.

Put each provisional sum and each prime cost sum on the register as its own entry, with the amount, what it is meant to cover and the allowance for the builder's profit and attendance on it. Draw against them as the work is instructed and watch what is left.

Por que: A sum folded into a rate is a sum nobody can release and nobody can adjust, so the contract sum adjustment at the end becomes archaeology. Held openly, both sides read the same figure and the final account is arithmetic.

Run the bill through validation for the item left at zero, the unit that contradicts its own description, the quantity that no longer agrees with the take-off it came from and the trade section that was never measured at all. Fix what it reports and run it again until it comes back clean.

Por que: One bill goes to every tenderer at once, so one mistake is priced by all of them. Catching it while the document is still yours costs an hour; catching it after the tenders are in costs a re-tender or a variation on day one.