How to bid roofing work as a subcontractor

What you are actually bidding

Settle the boundary before you measure anything. The roofing package lives in Division 07 Thermal and Moisture Protection, and on a commercial job it is split across sections that different subs can carry:

• 07 22 00 Roof and Deck Insulation. Polyiso, cover board, tapered fill. Sometimes yours, sometimes bought with the insulation or shell package.
• 07 50 00 Membrane Roofing. The low-slope waterproofing itself, whether that is membrane roofing in TPO, PVC or EPDM, or modified bitumen.
• 07 31 00 Shingles and Shakes on steep-slope work, plus underlayment, ice and water shield, starter and ridge.
• 07 62 00 Sheet Metal Flashing and Trim, 07 71 00 Roof Specialties (edge metal, coping, gravel stop) and 07 72 00 Roof Accessories (hatches, vents, walkway pads). Often a sheet metal sub's work, often yours.
• 07 27 00 Air Barriers. The wall air barrier has to terminate into your roof, and the transition detail is almost always drawn without naming who installs it.

Then the things that look like roofing and are not:

• The deck is not yours. Steel deck is 05 31 00 and wood sheathing is 06 16 00. You still care about it, because the fastener pull-out the manufacturer requires is a property of that deck, but you are not furnishing metal decking.
• Roof drains and overflows are plumbing. Plumbing furnishes and sets the drain body. You set the clamping ring, the target patch and the flashing. Overflow scuppers through the parapet get argued about every time, because the sleeve is sheet metal and the seal is yours.
• Curbs belong to whoever owns the equipment. Mechanical furnishes and sets the curb under an RTU, and you flash it. Same for pipe sleepers, conduit supports and every small penetration nobody drew.

Take a position on each of those in writing. A roofing bid that is silent on curb flashing, drain flashing and edge metal will be read as including all three.

Read the drawings for your sheets

• The roof plan gives you the outline, slope arrows, drain and scupper locations, crickets and the equipment layout. It gives you plan area, not roof area.
• Roof details and wall sections beat the roof plan. Base flashing height, coping, counter flashing and reglet, curb height, expansion joints and the air barrier tie-in are all in the details. The details carry more of your labour cost than the plan does.
• The specification is the assembly. Membrane type and thickness, attachment method (mechanically fastened, fully adhered, induction welded), cover board, vapour retarder, warranty term and the approved-installer requirement. The spec decides what you are pricing.
• Structural sheets tell you the deck type and gauge, which sets fastener type and pull-out, and whether the deck slopes or the insulation does.
• Mechanical and plumbing sheets carry the real penetration count. Count curbs, vents, drains and gas line supports off the M and P sheets, not off the roof plan, because the roof plan is usually drawn earlier and updated later.
• Envelope details tell you whether the parapet is your base flashing or the masonry sub's through-wall flashing. That one overlap shows up on nearly every job.

Getting the quantities right

Low-slope roofing is bid in square feet and in squares, one square being 100 sf. Steep slope is bid in squares too, but only after the slope conversion.

The obvious takeoff, plan area traced off the roof outline, misses four things:

1. The slope factor. Plan area is the footprint, not the surface. Roof pitch converts one to the other, and at 6:12 the slope factor is 1.118, so 1,000 sf of plan area is about 1,118 sf of roof. Take each pitch off separately. A job with 4:12 and 10:12 areas has two factors and two labour rates, and steep-slope areas also carry access and safety cost that low-slope does not.
2. Tapered insulation. Flat board is easy. Rigid insulation at a specified R-value converts from area to board count by panel size. Tapered fill to the drains does not. The board count comes off the manufacturer's tapered layout, it is driven by average thickness rather than the thickness at the low point, and that layout is usually not back before bid day. Carry it as a stated allowance with your assumed drain count and sump size written down.
3. Perimeter and corner uplift zones. The fastening pattern is not uniform. Field, perimeter and corner zones each have their own fastener density, and the corners are the densest. On a small footprint or a tall building the enhanced zones are a large share of the area, so a bid priced at the field rate across the whole roof is short on fasteners, plates and labour both. Measure the zones as separate areas rather than applying an average.
4. Everything that is not area. Base flashing, coping, edge metal, gutter, eave and fascia trim, reglet and expansion joint run in linear feet. Curbs, drains, vents, hatches and pitch pockets are each. Hips, valleys and ridges drive steep-slope waste and their own labour. These lines are where two roofing bids on the same building end up thousands apart.

On re-roof and recover work, add the quantity you cannot see. Take a test cut, write down the plies and the insulation you found, and state that as an assumption. Then price tear-off with a unit price per additional ply and per square of wet insulation, because you will find some.

The warranty writes the assembly

The gotcha that costs roofing subs the most money is treating the warranty as paperwork. It is not. A long-term no dollar limit manufacturer warranty dictates the components (approved cover board, approved fasteners at the approved density), the installer's certification status, a pre-job conference and a manufacturer inspection before the warranty issues. A material-only warranty on the same membrane is a different assembly at a different price. Read the warranty paragraph before you read the roof plan, price the roof it requires, and put the warranty term and type on the face of your proposal. Two roofing bids that look far apart are frequently two different warranties.

What the GC checks when leveling roofing bids

Bid leveling is the GC pushing every proposal onto one common scope so the numbers can be compared. Expect them to check:

• Squares carried, and whether you applied the slope factor to steep-slope areas.
• Warranty term and type, and whether you are an approved installer for the specified system.
• Insulation and cover board: in your number or in the shell package, and at what R-value.
• Tapered insulation: included, carried as an allowance, or excluded.
• Edge metal, coping and sheet metal: yours or the sheet metal sub's, item by item.
• Curb, drain and penetration flashing, and who furnishes the curbs.
• Tear-off and disposal, including your assumed ply count and who owns the dumpsters.
• Hoisting, access and phasing. Whether you are using the GC's crane or hoist, in what hours, and how many mobilizations you priced.
• Allowances and unit prices, so changes can be priced without re-bidding.

Anything you leave silent gets filled in with an assumption, and the assumption will not favour you.

Structure the proposal

A roofing proposal that survives leveling has five parts, in this order:

1. The number, with the squares carried, the membrane and thickness, the insulation R-value and the warranty term and type.
2. Inclusions, as items rather than a paragraph.
3. Exclusions, the same way. Deck and deck repair, roof drains and overflow bodies, equipment curbs, structural blocking, and any sheet metal you are not carrying.
4. Clarifications and assumptions. Tapered layout allowance, assumed ply count on tear-off, number of mobilizations, hoisting, temporary dry-in and night seals, weather and working hours, who provides the manufacturer inspection access.
5. Unit prices for the likely adds: per square of membrane, per square of wet insulation replacement, per linear foot of base flashing, per curb, per pitch pocket.

Price your markup on a cost you can defend line by line, and keep the takeoff that produced the squares. When the GC calls to level, the sub who can open the takeoff and show which sheet a quantity came from wins the conversation.

Where this fits

If you are on the other side of the table leveling roofing bids rather than submitting one, the same gaps read from the opposite seat. If you are running the takeoff itself, Ruh reads the drawing set, measures the scope, and prices the measured quantities against your own price book, with every line traceable back to the sheet it came from, which is what you need when a GC questions your squares.