Roofing

How to Read a Roof Replacement Estimate, Line by Line

A roof bid is mostly labor and disposal, and the line items that stay vague are exactly the ones that turn into a change order halfway through the tear-off.

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Roofing is priced by the square, which is 100 square feet of roof surface. A common single-story ranch is roughly 20 to 25 squares once you account for pitch and overhangs. Knowing the square count is the first step to comparing bids, because a contractor who measured 28 squares and one who measured 22 are not quoting the same roof, and one of them is wrong.

Tear-off and disposal

Tear-off is usually broken out separately, and it should be. A single layer of three-tab asphalt comes off far faster than two layers, and two layers means twice the dumpster. If your bid says "tear off existing roofing" with no layer count, ask what the estimator assumed and what happens if a second layer turns up. A good contractor will name a per-square adder in advance. A bad one will discover it on day one and hand you a number when the roof is already open.

Steep pitch and height matter too. Anything above roughly 7:12 needs staging and slows a crew noticeably, and a third story adds handling time. These are legitimate line items, not padding.

Decking: the line item that becomes a change order

Nobody can see the sheathing until the old roof is off, so decking replacement is always conditional. What separates a fair contract from a bad one is whether the conditional price is written down. You want a stated allowance, for example the first two sheets included, and a stated per-sheet price after that, with the sheet size and thickness named. Without that, "decking replaced as needed at market rate" is an open checkbook.

Ask what they will do about plank decking with gaps, which is common in older homes, and whether the shingle manufacturer's warranty requires overlay sheathing in that case. It often does.

Underlayment, ice barrier and drip edge

Synthetic underlayment has largely replaced felt and is worth having: it tears less, walks better wet, and can be left exposed longer if weather interrupts the job. Felt at 15 pound weight is the cheap option and shows up in low bids.

Ice and water shield is a self-adhering membrane at eaves, valleys and penetrations. In cold climates code typically requires it to extend to a point 24 inches inside the exterior wall line, which on a low slope roof can mean two courses, not one. Valleys and around chimneys and skylights deserve it in any climate. If a bid does not mention valleys, that is a gap.

Drip edge is inexpensive metal at the eaves and rakes that keeps water off the fascia. It is required by current code in most jurisdictions, and its absence from a bid is a reliable sign that the estimator is writing to a price rather than to the roof.

Ventilation is part of the roof, not an upgrade

Shingle warranties are conditioned on adequate attic ventilation, and inadequate ventilation is the most common reason a roof ages early. The usual target is one square foot of net free vent area per 150 square feet of attic floor, split roughly evenly between intake at the soffits and exhaust at the ridge. A ridge vent installed over blocked soffits does almost nothing. Ask specifically whether the bid includes opening up intake, because that work happens from below and is often skipped.

Also watch for a bid that mixes exhaust types. Adding a ridge vent while leaving powered fans or box vents in place lets the ridge pull air from the other openings instead of from the soffits.

Warranty language

There are two warranties and they are not related. The material warranty comes from the shingle manufacturer and covers defects, prorated over time in most cases. The workmanship warranty comes from the contractor and covers installation. Manufacturer enhanced warranties, the ones that cover labor too, generally require a certified installer and a full system of that brand's underlayment, starter and ridge cap. If a bid advertises an enhanced warranty, the accessory line items should match the brand.

Comparing three bids fairly

Normalize on squares first, then check that all three include the same underlayment class, the same ice barrier coverage, drip edge, new pipe boots, new step flashing rather than reused, and a stated decking allowance. A bid that is 20 percent lower almost always differs on two or three of those items, and once you add them back the spread usually collapses. Ask for proof of general liability and workers compensation coverage in the contractor's name, and confirm who pulls the permit.