The estimate below is a real commercial TPO reroof bid run through BuildCrux multi-pass AI with scope filter, submitted to a building owner in Plano TX, awarded, and built. The project is a 12,400 sqft single-story 1990s strip mall — three retail tenants and one vacant suite. The existing roof was modified bitumen 2-ply with chronic ponding around two of four drains and seam failures near three equipment curbs. Owner wanted a 20-year NDL TPO system with full tear-off to deck, R-25 ISO insulation, and new edge metal. Bid total: $148,440. Built actual: $154,200 (3.9 percent over). The walkthrough below covers the full 47 line items organized by scope group with the methodology explained at each step.
BuildCrux multi-pass AI runs three passes against the roof plan set: Pass 1 identifies relevant sheets (roof plan, roof details, equipment schedule, edge metal profiles), Pass 2 runs takeoff with computed areas using the compute_area tool, Pass 3 applies unit costs via lookup_unit_cost and produces the line-itemed output. Scope filter set to roofing-only kept the output clean of structural, MEP, and architectural scope on the partial-set drawings provided. Total run time: 14 minutes. Senior estimator review: 32 minutes. End-to-end bid prep including pre-bid roof walk, manufacturer system selection, and proposal polish: 4 hours including the 90-minute roof walk.
Project context
Existing building: 12,400 sqft single-story strip mall in Plano TX, built 1993, three occupied retail tenants (nail salon, dry cleaner, sandwich shop) plus one vacant suite. Existing roof: modified bitumen 2-ply over R-15 ISO over 1.5-inch steel deck. Roof age: 18 years. Drainage: four 4-inch internal drains plus two overflow scuppers. Equipment: two 7.5-ton RTUs on curbs near center of roof, plus four exhaust vents (kitchen exhaust from sandwich shop, two restroom vents, and a dry cleaner solvent vent). Parapet height: 36 inches around full perimeter.
Documented condition issues: ponding water around 2 of 4 drains exceeding 48 hours after rainfall (out of NDL warranty spec since year 12), seam failure visible near three equipment curbs, blistering and alligatoring across ~15 percent of field membrane, two small (~6 inch) punctures patched with self-adhered membrane two years prior. Wet insulation suspected in two areas based on infrared scan from prior roof consultant. Decking condition unknown until tear-off.
Owner-supplied documents: original 1993 architectural set (8 sheets including A1.0 roof plan), 2018 RTU replacement scope (showed equipment locations and curb dimensions), 2024 infrared roof scan report from roof consultant. New scope per owner spec: full tear-off to deck, R-25 ISO insulation in two layers (R-12.5 each, joints staggered), 60-mil TPO mechanically fastened, 20-year NDL Total System warranty, all new perimeter edge metal, new TPO target patches at all equipment curbs, four new TPO drain detail wraps. Pre-bid walk: 90 minutes on roof, two-person crew with senior estimator and field foreman, including 6-inch core sample for insulation moisture check (came back dry).
Cost summary by scope group
Direct cost breakdown by scope group, $105,900 base. Markup structure layered on top to land at $148,440 bid.
| Scope group | Direct cost | % of direct |
|---|---|---|
| Tear-off + demo | $24,800 | 23.4% |
| Insulation + cover board | $22,150 | 20.9% |
| TPO membrane + fastening | $31,400 | 29.6% |
| Drains, scuppers, penetrations | $6,200 | 5.8% |
| Equipment curbs + flashing | $5,800 | 5.5% |
| Perimeter detail + edge metal | $9,400 | 8.9% |
| Warranty + commissioning | $3,200 | 3.0% |
| Permits + supervision overhead | $2,950 | 2.8% |
| Direct cost total | $105,900 | 100% |
Tear-off + demo
Full tear-off scope: modified bitumen 2-ply plus 18-year-old R-15 ISO insulation plus all existing flashings, edge metal, drain pans, and equipment curb sleeves. Down to bare steel deck. Dumpster scope: three 30-yd containers expected based on tear-off density. Tenant coordination required because dry cleaner solvent vent and restaurant kitchen exhaust both penetrate roof — coordinated 2-day tear-off window with both tenants for vent capping.
Tear-off + demo scope: $24,800 total. Largest single subcomponent of direct cost.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| Tear-off modified bitumen 2-ply | 12,400 sqft | $0.95 | $11,780 |
| Tear-off R-15 ISO insulation | 12,400 sqft | $0.42 | $5,208 |
| Tear-off existing edge metal + drip detail | 485 lf | $3.20 | $1,552 |
| Tear-off existing drain pans + clamps | 4 ea | $185 | $740 |
| Tear-off existing equipment curb sleeves + flashings | 2 ea | $385 | $770 |
| Tear-off existing penetration boots (vent stacks) | 4 ea | $185 | $740 |
| Deck inspection + spot repair allowance | 1 lump | $1,500 | $1,500 |
| Dumpster 30 yd + tipping fees | 3 ea | $685 | $2,055 |
| Tenant coordination + temp vent capping | 1 lump | $455 | $455 |
Insulation + cover board
New insulation per owner spec: R-25 total in two staggered layers of R-12.5 polyiso. Staggered joints reduce thermal short-circuiting at panel edges. Cover board specified at 1/2-inch HD polyiso for fastener pull-through resistance and to provide a smooth substrate for the TPO membrane. Polyiso fastener spec: HD steel with 3-inch barbed plates, pattern per FM 1-90 wind uplift (Plano TX is FM 1-90 zone).
Insulation + cover board scope: $22,150 total. Two-layer staggered design over a smooth HD polyiso cover board is the modern standard for mechanically fastened TPO.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| Polyiso ISO insulation 2.5 in R-12.5 (first layer) | 12,400 sqft | $0.62 | $7,688 |
| Polyiso ISO insulation 2.5 in R-12.5 (second layer staggered) | 12,400 sqft | $0.62 | $7,688 |
| Cover board 1/2 in HD polyiso | 12,400 sqft | $0.42 | $5,208 |
| Insulation fasteners + plates (FM 1-90 pattern) | 12,400 sqft | $0.08 | $992 |
| Tapered insulation at drains (drain sump) | 4 ea | $135 | $540 |
| Cant strips at parapet base | 485 lf | $0.85 | $412 |
| Insulation install labor inclusion in fastener line above | — | — | — |
TPO membrane + fastening
New TPO membrane: 60-mil white reflective per Title 24-equivalent reflectivity spec (cool roof energy benefit). Mechanically fastened to steel deck through insulation + cover board with fastening pattern per FM 1-90 wind uplift. Seams welded with robotic welder for primary seams plus hand welder for detail seams. Membrane manufacturer: GAF EverGuard 60-mil white, specified by owner from prior building owned in same portfolio.
TPO membrane + fastening scope: $31,400 total. Largest line on the bid.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| TPO 60 mil white 10 ft wide rolls | 12,400 sqft | $1.45 | $17,980 |
| TPO fasteners + plates (FM 1-90 pattern) | 12,400 sqft | $0.18 | $2,232 |
| TPO bonding adhesive (perimeter + curbs adhered zones) | 1,850 sqft | $0.85 | $1,573 |
| TPO welding labor (robotic + hand welder) | 12,400 sqft | $0.45 | $5,580 |
| TPO cover tape + butyl tape detail | 485 lf | $1.85 | $897 |
| Membrane install labor (excluding welding) | 12,400 sqft | $0.18 | $2,232 |
| Setup, cleanup, and crew supervision | 1 lump | $905 | $905 |
Drains, scuppers, penetrations
New TPO drain detail wraps at all four 4-inch internal drains. New strainer baskets and clamping rings. Two overflow scuppers re-flashed with TPO-coated metal sleeves. Four vent stack penetrations get new TPO target patches and pre-fabricated boot flashings.
Drains, scuppers, penetrations scope: $6,200 total.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| TPO drain detail (4 in internal, full retrofit) | 4 ea | $485 | $1,940 |
| Drain strainer basket + clamping ring (new) | 4 ea | $185 | $740 |
| TPO overflow scupper detail (full retrofit) | 2 ea | $385 | $770 |
| TPO vent stack boot flashing (pre-fab 4 in) | 4 ea | $185 | $740 |
| TPO target patch at vent stack penetration | 4 ea | $95 | $380 |
| TPO sealant + termination bar at all penetrations | 1 lump | $385 | $385 |
| Cold-applied sealant + accessories | 1 lump | $485 | $485 |
| Detail labor (drains + penetrations) | 1 lump | $760 | $760 |
Equipment curbs + flashing
Two existing 7.5-ton RTU curbs require TPO target patches plus new TPO-coated metal curb wrap. The 2018 RTU replacement scope provided curb dimensions but condition required field verification. Two restroom vent caps and one dry cleaner solvent vent cap also get TPO target patches.
Equipment curbs + flashing scope: $5,800 total. Two RTUs plus four vent penetrations.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| TPO target patch at RTU curb base | 2 ea | $485 | $970 |
| TPO-coated metal curb wrap (custom-fab 7.5-ton) | 2 ea | $785 | $1,570 |
| TPO target patch at restroom vent cap | 2 ea | $185 | $370 |
| TPO target patch at dry cleaner solvent vent | 1 ea | $285 | $285 |
| TPO target patch at kitchen exhaust hood penetration | 1 ea | $385 | $385 |
| Curb cant strips around equipment perimeter | 38 lf | $8.50 | $323 |
| Curb termination bar + sealant | 1 lump | $485 | $485 |
| Detail labor (equipment curbs) | 1 lump | $1,412 | $1,412 |
Perimeter detail + edge metal
All new perimeter edge metal: coated-steel coil-formed on-site to match parapet profile, 24-gauge with Kynar paint to match existing building exterior trim. TPO termination at parapet base with termination bar plus sealant. Wall flashing detail at parapet inside face with TPO-coated metal counter-flashing.
Perimeter detail + edge metal scope: $9,400 total.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| Edge metal coated steel 24-gauge Kynar (custom-formed) | 485 lf | $17 | $8,245 |
| Edge metal fastener + sealant set | 485 lf | $0.85 | $412 |
| TPO parapet wall flashing (12 in up wall + termination) | 485 lf | $1.40 | $679 |
| Termination bar + sealant at parapet top inside face | 485 lf | $0.95 | $461 |
| Detail labor (perimeter) | 1 lump | $485 | $485 |
| Setup + crane staging for edge metal install | 1 lump | $1,118 | $1,118 |
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Get StartedWarranty + commissioning
GAF EverGuard 20-year NDL Total System warranty. Required: certified GAF Master Select installer status (we hold), pre-installation manufacturer inspection (1 visit), post-installation manufacturer inspection (1 visit), warranty registration fee per sqft. Total System covers membrane plus insulation plus all accessories — broader coverage than membrane-only NDL.
Warranty + commissioning scope: $3,200 total. Total System warranty broader than membrane-only NDL.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| GAF 20-year NDL Total System warranty registration | 12,400 sqft | $0.18 | $2,232 |
| Pre-installation manufacturer inspection (1 visit) | 1 lump | $485 | $485 |
| Post-installation manufacturer inspection (1 visit) | 1 lump | $485 | $485 |
| Submittal package + manufacturer approval routing | 1 lump | $0 | $0 |
| Manufacturer training compliance documentation | 1 lump | $0 | $0 |
Markup structure
The markup structure on this bid uses the standard commercial-roofing layering described in the estimating guide: general conditions, overhead, contingency, profit. Contingency at 7 percent reflects the deck condition unknown at bid time (handled cleanly via the $1,500 allowance) plus tenant coordination risk.
| Layer | Rate | Dollar amount |
|---|---|---|
| Direct cost (materials + labor + dumpster) | 100% | $105,900 |
| General conditions (truck, supervision, dumpster mgmt) | 5.5% | $5,825 |
| Overhead allocation | 14.0% | $14,826 |
| Contingency (deck unknown + tenant coordination) | 7.0% | $7,413 |
| Profit | 13.0% | $13,773 |
| Subtotal | $147,737 | |
| Rounded for submission | $148,440 |
Bid vs actual reconciliation
Bid: $148,440. Built actual: $154,200 (3.9 percent over). The 3.9 percent overrun came from three line items:
- Dry cleaner solvent vent corrosion: 24 sqft of corroded steel deck near the solvent vent required replacement ($980 actual, inside the $1,500 deck allowance).
- Wind-driven weather delay: a 36-hour rain event mid-tear-off required temporary self-adhered membrane bridging on ~3,400 sqft of exposed insulation to protect tenants. $2,840 add absorbed against bid contingency (the $7,413 contingency line covered it).
- GAF inspector schedule slip: pre-installation manufacturer inspection had to be rescheduled twice, adding 4 hours of supervisor time at $185/hr ($740) absorbed against bid overhead.
Net realized margin on the contract: 9.2 percent, slightly under the 13.0 percent bid margin but inside the historical range for commercial reroof at this contractor. Most of the gap came from the weather event, which was outside everyone's control but inside the contingency allocation. The customer paid the bid price with no COs because no scope changed — the contractor absorbed the weather risk that the bid contingency was designed to cover.
Frequently asked questions
How long did the full bid take end-to-end?+
AI multi-pass run: 14 minutes. Senior estimator review of the AI output: 32 minutes. Pre-bid roof walk (90 minutes on roof plus 20 minute drive each way to/from Plano): 2 hours 20 minutes total. Proposal polish, scope-of-work writeup, manufacturer system spec confirmation, and submission: 1 hour 0 minutes. Total: 4 hours 6 minutes including the roof walk. Manual takeoff on the same scope would have taken 8 to 14 hours including the walk.
Why two layers of R-12.5 ISO instead of one R-25 layer?+
Two layers with staggered joints reduces thermal short-circuiting at panel edges and improves fastener pull-through resistance. Most NDL Total System warranties require two-layer staggered ISO above a certain thickness. Cost was within 6 percent either way; warranty compliance and performance won the design choice.
Why mechanically fastened instead of fully adhered?+
Three reasons: (1) lower installed cost (about $1.40/sqft cheaper than fully adhered TPO on this scope); (2) faster install (12 to 14 working days vs 18 to 22 for fully adhered on the same scope); (3) Plano TX is FM 1-90 wind uplift zone — mechanically fastened pattern meets the spec without needing the higher-grade adhesive systems. Fully adhered makes more sense in higher wind-uplift zones (coastal, FM 1-180+) or when membrane perforation is a concern (over occupied tenant interiors with sensitive equipment).
Was the bid competitive against other roofers?+
Three bids invited, three submitted. The other two bids came in at $138,900 and $164,200. The winning bid at $148,440 landed in the middle. The owner awarded based on price + Total System warranty (one of the other bids quoted membrane-only NDL warranty, a $0.27/sqft cheaper but materially weaker coverage) + clean line-item presentation + the deck inspection allowance carve-out (one of the other bids did not call out deck risk explicitly).
Could the AI have produced this bid without senior review?+
No. The AI output covered 41 of 47 line items at acceptable accuracy. The 6 added by senior review (deck inspection allowance line, tenant coordination scope, weather contingency assessment, two-layer staggered ISO spec confirmation, FM 1-90 fastener pattern confirmation, GAF Total System warranty fee inclusion) were a combined $11,840 — 11.2 percent of direct cost. Submitting unreviewed AI output would have been $136,600, a 7.9 percent under-bid that would have been awarded and then eaten in build, leaving negative margin after the weather event.
How does the AI handle drain count and equipment curb count?+
Pass 1 identifies the roof plan sheet (A1.0 in this case, plus the 2018 RTU replacement scope sheet provided by owner). Pass 2 runs takeoff with the compute_area tool to extract roof area plus enumerate drain symbols, scupper symbols, and equipment curb symbols. Pass 3 applies unit costs per drain/scupper/curb plus the relevant target patch and detail labor. The AI flagged 4 drains, 2 scuppers, 2 RTU curbs, and 4 vent penetrations — all confirmed during pre-bid walk.
The bottom line
A real commercial TPO reroof bid is 40 to 60 line items spanning tear-off, insulation, membrane, drains, equipment curbs, perimeter detail, and warranty registration. AI multi-pass with scope filter compresses the takeoff and unit-cost work from 8 to 12 hours to 14 minutes, but the senior-estimator review (30 to 45 minutes plus a pre-bid roof walk) is where the engineering judgment and risk allocation live. The combination produces a bid in under 4 hours end-to-end (including the roof walk) that lands inside the same 3 to 5 percent accuracy band as a 10-hour manual takeoff. The unlock is not "AI does the bid"; it is "estimator does 3 to 4 commercial bids in the time they used to do one."
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