Check which documents each contractor received
A lower quotation does not establish that a contractor can deliver the same work for less. Before comparing totals, check whether every company priced the same information: project version, quantities, specifications and clarifications. Different issue dates can conceal a substantial change. Record what was sent and share answers that alter the requested scope with all the companies involved.
If the design remains preliminary, treat the figures as information appropriate to that level of definition. An approximation based on a few plans is not equivalent to a detailed quotation based on a complete document package. Ask which assumptions each contractor used. Your first task is to understand the work actually being priced, before deciding whether the financial result is competitive or sufficiently clear to support an appointment and a properly understood construction agreement.
Align work sections, units and quantities
Prepare a table using the reference work items, with a column for each quotation. Check description, unit, quantity, rate and subtotal. Where a contractor groups several tasks into one amount, request a breakdown that makes the included work identifiable. Do not force an equivalence between an item priced by area and an all-in amount without clarifying what each covers.
Flag differences in quantities for checking against the project information. A smaller quantity may reflect a different measurement approach or an omission rather than a cheaper rate. Avoid independently correcting technical quantities without professional confirmation. Your comparison table should locate questions: why an item is absent, where a task is included and what explains a discrepancy. Keep the answers with the relevant quotation so that later comparisons retain their context and do not rely on memory.
Look for gaps at the edges of each package
Differences often emerge at interfaces: who prepares a substrate, removes waste, finishes a junction or connects equipment. Read the notes as carefully as the financial summary. Where relevant, ask about temporary protection, access equipment, transport, supporting tasks and reinstatement of affected elements. Do not assume every item is needed for your project or that a general description automatically includes it.
Identify client-supplied products and separately appointed work too. For each interface, record who supplies, who installs and who checks compatibility. Buying an item separately may introduce coordination that has no named owner yet. Close scope gaps before adding totals, because assigning an imagined cost to an exclusion does not establish who will actually do the work or under which conditions. A clear boundary is more useful than a superficially complete spreadsheet.
Check specifications and proposed alternatives
Items with the same name may offer different products or performance. Read their technical descriptions and ask contractors to identify alternatives wherever they depart from the requested specification. Comparing brands alone is insufficient: establish whether the project requirements are maintained and what the substitution means for use, maintenance, compatibility or appearance.
Take those alternatives to the technical team for assessment. A saving should not be accepted simply because a catalogue describes a product as equivalent. Ask the quotation to distinguish the specified solution from the proposed variant, including the price difference and associated conditions. If a selection remains open, request an explanation of the provisional pricing basis and how it will be adjusted later. An allowance without an agreed adjustment method can make the eventual comparison difficult and leave uncertainty about what the stated total will actually buy.
Read the conditions attached to the figure
Check quotation validity, how taxes are presented, payment arrangements and the proposed process for variations. Ask what information the contractor needs to organise its programme and which dependencies it recognises: access, selections, deliveries or earlier work. An indicative date is different from a commitment still dependent on unresolved conditions, so make those conditions visible in the discussion.
Compare how progress will be evidenced and additional work documented. A proposed modification should be traceable to an identifiable request and valuation. Spain’s Building Act distinguishes the contractor from other participants in the building process; a construction quotation does not establish that every technical service is included. Discuss the allocation of responsibilities and appropriate contract documentation with the relevant professionals, especially where separate contractors or suppliers are involved. This helps turn a price comparison into an understandable description of the work being offered.
Request clarified offers on a common basis
Send each company numbered questions and request a response incorporated into its proposal. Use a common reference where a clarification affects all quotations. Retain the initial offer, questions and final version, while identifying exactly which version you are comparing. Record unresolved matters instead of hiding them inside an adjusted figure that no contractor has accepted.
The final comparison should explain price, scope, exclusions, alternatives and significant conditions. It may reveal that the work needs further definition before a sound choice is possible. That is useful information because it exposes a gap before appointment. To prepare a discussion with F5, summarise the project stage and the differences you do not understand, without sending unnecessary confidential documents. Our guide to recording layout changes can help organise modifications that emerge while contractors are preparing or clarifying their offers.
Projects and next steps
Sources and references
Published: 25 October 2026. Requirements and documents must be checked for each property and proposed intervention.