Connect a site layout to a transparent development pro forma

Price a saved layout, not an unrelated area estimate

Open Layout & pro forma for the selected saved scheme and find Does this option pencil? This estimate belongs to that site layout; the separate Residential costs & returns view belongs to the residential model. Building construction uses the modeled gross floor area; an area-based sale or rental assumption uses the modeled net floor area. For countable programs, an appropriate home or room basis may be available. Check both the revenue mode and measurement basis before entering a number.

A different layout can change several cost drivers at once. A larger building may also need more circulation, a longer road or a different parking program. Copying only the original construction subtotal into a larger option hides those changes. PARCIC remeasures the supported geometric scope for the selected concept before applying its entered prices.

Separate measured scope from an allowance

The site estimate distinguishes building area, paved surfaces, placed parking and road-centerline length. Paved area is measured as a non-overlapping union of roads, stalls and circulation. A per-space marking rate covers markings; a road-infrastructure rate needs to exclude paving already priced by area.

Earthwork, utility runs and drainage quantities are unavailable in this concept model. Their costs are explicit allowances rather than measured takeoffs. Add the applicable permits, demolition, offsite works or other scope under a clearly described allowance, and record what the quoted rate includes. An empty cost means unpriced, not free.

A deliberate zero can be a valid reviewed assumption, but it needs a reason. For example, entering zero for a road line because no road exists in that option differs from entering zero for unknown utility upgrades. The first follows the measured scope; the second could conceal a material project cost.

A worked comparison that stops at the right conclusion

The fictional table holds teaching rates constant while changing two layouts. Building work is $250 per gross sq ft, paving $8 per paved sq ft, stall marking $100 per placed space and additional road infrastructure $100 per centerline foot. These are arithmetic assumptions, not contractor quotes or local market evidence.

Option B adds $514,200 across these four lines. That is a useful design-cost difference, not a complete development-cost difference or a return. Neither option includes land, closing, allowances, soft costs, contingency, carrying or disposition costs in this table. If utility scope remains unknown, preserve that missing input rather than choosing the option with the more attractive incomplete margin.

Complete the revenue and schedule assumptions

For a sale case, record the price basis and disposition costs. For a rental case, review the month or year basis, vacancy, operating costs, holding period and exit capitalization assumption. A hotel case uses room-night pricing and entered occupancy. These are different income models; a price copied from another building type may not have a valid basis.

Timing matters as well as total cost. The layout model includes predevelopment, construction and hold periods, a carrying allowance and monthly unlevered cash flows. Prices and schedules remain user assumptions. A complete output is a conditional, nominal-USD, pre-tax, unlevered comparison; it does not model a lender’s debt structure, tax effects, grants, rent growth or price appreciation.

Required unpriced inputs and unresolved layout blockers withhold dependent returns. An unresolved parking target should not be hidden by filling every cost field. Likewise, a complete financial form cannot establish permitted use, utility capacity or a construction delivery commitment. Review the evidence and the model limitations alongside any metric.

Test what would change your decision

Begin with one documented set of assumptions, then change a material driver: a contractor’s revised scope, a lower supported sale price, a different unit mix or a longer predevelopment period. Record which input changed and compare the same output basis. If several inputs change together, explain the scenario rather than presenting it as a measured market forecast.

The GAO Cost Estimating and Assessment Guide identifies scope, schedule, technical baseline, assumptions, data, sensitivity analysis and updates as components of reliable estimating. Those general principles support the discipline of keeping an estimate traceable; the guide is not a local construction price source or an endorsement of PARCIC.

Use the worksheet to connect each consequential rate to a quote or observation date. Ask whether two allowances overlap, whether operating expenses include the intended scope and whether the schedule is supported. The next useful action may be obtaining one missing quote instead of calculating another precise-looking return.

Keep the comparison attached to its version

Save or discard draft changes before switching schemes. Saved financial results carry the linked concept receipt and calculation version. Changing the building type can require new pricing assumptions; changing geometry requires supported quantities and outputs to be recalculated. A stale result is not a valid comparison simply because it was once saved.

Where schemes have the same building type, you can apply saved assumptions across them while each layout is priced from its own quantities. Review each option’s blockers and missing inputs. Use the saved report or available exports to communicate the version, assumptions and unresolved scope, then have your project team check the complete property-specific case before commitment.

Official references

• U.S. GAO: Cost Estimating and Assessment Guide

  General estimating discipline covering scope, assumptions, data, sensitivity and updates. It supplies no property-specific rates and does not validate a PARCIC output.

  Reference retrieved 2026-10-18. This date does not establish a rule’s effective date or a property’s eligibility.