Justifier une estimación par ses números generadores

Load the catalogo de conceptos exactly as it was awarded: every concepto with its clave, its unit, its contract quantity and its precio unitario. Do not tidy it, do not merge lines and do not renumber. The estimacion pays these lines and nothing else, so the catalogo is the only list a generador is allowed to point at.

Pourquoi: A generador written against an activity, a floor or a crew has nowhere to land, because the estimacion is settled concepto by concepto and the reviewer works down the catalogo. Renumbering is worse than measuring wrongly: a wrong volume is corrected in the next period, a renumbered catalogo makes every past estimacion unreadable against the current one.

Take the period off the drawings, subdivided the way the generador will show it: by eje, by nivel, by tramo or by whatever grid the works are actually built on. Record the sheet number and the revision each figure came from as you measure, not afterwards.

Pourquoi: Drawings are reissued mid job and the reviewer will be holding a different revision from the one you measured. A generador that names its sheet and revision can be rechecked in a minute; one that does not has to be measured again from scratch by somebody who was not there, and the volume that comes back is never the one you claimed.

For each concepto write the generador the reviewer will read: the location, the dimensions as measured, the arithmetic that turns them into a volume, and the total. Where the shape is not obvious, the croquis goes with it. Show the cumulative volume and the volume claimed this period side by side, because the estimacion pays the difference between two cumulative figures and not a figure of its own.

Pourquoi: The residencia de obra checks generadores, not totals, and it has fifteen days under article 54 LOPSRM to review and authorise before the twenty natural day payment period can start. A total with nothing behind it cannot be authorised inside those fifteen days even by somebody who believes you, so it comes back, and the period starts again with the next estimacion rather than with this one.

Where a generador covers work that was instructed, varied, accelerated or executed under a condition the contract did not foresee, cite the nota de bitacora that recorded it. The bitacora de obra is the instrument of communication between the parties under the reglamento of the LOPSRM, so the note is not a memory aid, it is the paper the instruction lives on.

Pourquoi: At the finiquito the question is almost never whether the work was built. It is whether it was ordered, by whom and on what date, and a generador that cannot name its nota is a volume the reviewer has no way to accept without taking your word for it. Nobody signs a finiquito on somebody's word.

Where a generador runs past the contract quantity, or measures something the catalogo does not carry at all, lift it out of the estimacion and raise it as a concepto extraordinario or fuera de catalogo, with its own precio unitario integrated the way the reglamento requires and its own authorisation. Put it back into an estimacion only once it has been authorised.

Pourquoi: An extraordinario carried quietly inside an ordinary line is the most common reason a Mexican finiquito does not close. It passes while nobody is looking at that concepto, it fails at the audit that reads the catalogo against the paid volumes, and by then the work is a year old and the people who agreed it verbally have moved on.

Carry each generador total onto its concepto line, price it at the awarded precio unitario, and hand the estimacion over as one package: the lines, the generadores, the croquis, the photographs and the test results the specification calls for. Record the date you presented it, separately from the date it is authorised.

Pourquoi: Two different dates drive two different obligations under article 54 LOPSRM, and keeping only one of them is how a contractor loses an argument it was winning. The presentation date is what shows you met the cut-off; the authorisation date is what starts the twenty natural days for payment. Written down as they happen, both are facts. Reconstructed later, both are claims.