One Row at the Eave May Not Be the Same Roof

Two roofing proposals can both include ice and water shield and still describe materially different work. One contractor may plan a single roll width along the eave. Another may extend the membrane far enough up the slope to reach beyond the exterior wall below. Those plans are not necessarily equivalent. Before choosing between the bids, ask each roofer to state where the membrane will be installed and how far it will extend.

This detail matters in St. Louis because winter temperatures regularly move above and below freezing. Snow or ice can melt on a warmer section of roof and refreeze near a colder eave. Water can then collect behind that ice and move under shingles. Shingles are designed to shed water moving down the roof. They are not a sealed surface against water moving uphill.

Ice and water shield is a self adhering membrane installed on the roof deck before the shingles. It seals more closely around fasteners than ordinary synthetic underlayment. It is commonly used at vulnerable locations such as eaves, valleys, roof to wall intersections, and around penetrations. Its presence in a material list does not tell you how much will be used or where it will go.

Roofer comparison

Start by finding the underlayment section in each proposal. Look for a specific membrane location, not merely the words ice and water shield. A useful scope might identify the eaves, valleys, chimney area, skylights, plumbing penetrations, and any low slope transition where the product is planned.

At the eave, ask how the contractor determines the upper edge of the membrane. A roll is commonly three feet wide, but three feet measured along the roof deck does not always reach three feet horizontally into the house. Roof pitch changes that relationship. A wide soffit also places the exterior wall farther back from the roof edge. On a house with a steep pitch or deep overhang, one course of membrane may stop above the soffit instead of reaching beyond the wall line.

That is why the phrase one row is incomplete. The useful measurement is where the membrane ends in relation to the exterior wall below. Many adopted residential code provisions use a point at least 24 inches inside the exterior wall line as the reference for an ice barrier. Local requirements and amendments can differ, and St. Louis County contains many separate municipal permit desks. The contractor should confirm the requirement for the address where the work will occur.

Compare valley language just as closely. A proposal that says membrane at valleys is clearer than one that lists a roll of membrane without assigning it to a location. Ask whether the valley membrane will run continuously from the bottom to the top and whether it will be installed directly on sound decking. If two roof planes meet above an addition, porch, or garage, make sure that valley is counted rather than treated as an incidental detail.

Roof to wall intersections deserve their own line. These are places where a sloped roof ends against siding, brick, or another wall. The membrane is not a substitute for step flashing, counterflashing, or kickout flashing. It is an added layer beneath those parts. A proposal should not use membrane language to avoid identifying the metal flashing work.

Also compare what happens after tear off. Self adhering membrane needs a suitable surface. Rotten decking, wide gaps, loose boards, dirt, and old fasteners can interfere with installation. Older St. Louis houses may have plank decking rather than sheet decking. The proposal should explain how unsuitable deck areas are identified and priced before new underlayment is installed.

Put the two bids into the same columns

• Eaves: Record the number of courses and the stated endpoint in relation to the exterior wall.
• Valleys: Count every valley and note whether membrane is specifically included.
• Walls and chimneys: Separate the membrane from the flashing work.
• Penetrations: List skylights, plumbing vents, attic vents, and other openings individually.
• Deck condition: Note the written rate or method for replacing unsuitable wood.
• Permit requirement: Identify which municipality will review the job and who will confirm its adopted rule.

This comparison can expose a price difference that initially looks like labor markup. One bidder may have included additional membrane courses, valley coverage, and deck preparation. The other may have entered one generic allowance. You cannot tell which scope fits the house until the quantities and locations are stated.

What it costs

The material itself is only part of the cost. Additional eave coverage requires more rolls, more cutting, and more installation time. Complex roofs require short pieces and careful fitting around corners. Valleys and wall intersections also slow the work because the crew must keep the membrane flat, overlap it correctly, and avoid trapping debris beneath it.

Ask for the membrane cost to remain inside the total roofing scope whenever the locations can be measured before work begins. Eave length, roof pitch, soffit depth, valleys, chimneys, and most penetrations can be observed during an inspection. A contractor should not need to wait for tear off to decide whether the house has four valleys or eight plumbing vents.

Deck repairs are different because concealed wood may not be visible until the old roof is removed. That uncertainty does not prevent comparison. Each bidder can state a unit price for sheet decking, plank replacement, or another defined repair method. The important point is that the rate and measurement method appear in writing before the roof is open.

Do not compare bids by the number of membrane rolls alone. Roll dimensions can differ, and waste varies with the roof layout. A quantity without a placement plan is hard to verify. Compare finished coverage instead. Ask each bidder to show the intended areas on a roof diagram or mark them on inspection photographs.

A lower price may be reasonable if the roof has short overhangs, few intersections, and no complicated valleys. A higher price may also be reasonable if the design needs a second eave course or extensive transition coverage. The homeowner needs the geometry behind the number, not a general statement that one system is better.

What to ask

1. Where exactly will self adhering membrane be installed? Ask the roofer to name every eave, valley, wall, chimney, skylight, and penetration included in the scope.
2. How far will it extend past the exterior wall line? This is more useful than asking whether the bid includes one row.
3. Did you account for the soffit depth and roof pitch? Both affect where a standard width ends.
4. Which permit office has authority over this address? A St. Louis mailing address does not identify the governing municipality. The roofer should confirm the adopted requirement with the correct desk.
5. Is the membrane installed directly on the decking? Ask how old underlayment, loose material, and unsuitable wood will be handled.
6. What flashing is included above the membrane? Step flashing, counterflashing, apron flashing, and kickout flashing should be identified separately where applicable.
7. How will I verify coverage before shingles hide it? Request photographs showing the eaves, valleys, and intersections after membrane installation and before the field shingles cover them.
8. What changes require my written approval? If additional membrane becomes necessary after tear off, the quantity, reason, and price should be recorded before that added work proceeds.

Photographs are especially useful because this layer disappears early in the installation. A wide photograph can establish the roof area, while closer photographs can show overlaps and the relationship between the membrane and wall line. Keep those images with the proposal, permit record, material information, and final invoice.

If one bidder cannot describe the membrane beyond saying it is included, ask for the scope to be revised. The revision does not need technical language or a long product description. It needs locations, coverage, and a method for handling unexpected decking. Those points let you compare the roof that will actually be built.

Keys Roofing can inspect the eaves, measure the overhang and pitch, count the valleys and penetrations, and put the proposed membrane coverage in writing. To schedule a roofing inspection in the greater St. Louis area, call (314) 220-2333.