Low slope
Built-up and modified bitumen roofing
Multi-ply low-slope roofs, installed and repaired by manufacturer-licensed crews and kept working through scheduled inspection and maintenance.
Chapter 01
How a multi-ply roof ages: blisters, alligatoring, open laps and tired flashings
A built-up roof is made of layers: a base sheet, several plies of reinforcing felt set in bitumen, and a surfacing on top, either a flood coat with gravel or a granule-surfaced cap sheet. Modified bitumen follows the same multi-ply logic with polymer-modified sheets that are torched, mopped or cold-applied in laps. Both systems are redundant by design, which is why they last, and also why their failures are slow and easy to miss.
The surface goes first. Sun and weather dry out the top coat until it cracks in a pattern roofers call alligatoring, and granules wear off a cap sheet where water runs or foot traffic concentrates. Blisters come from moisture or air trapped between plies, and a blister that has been walked on can open into a leak. Laps that were not fully bonded show up as open edges and fishmouths that let water run between the layers.
The details give out before the field does. Base flashings at curbs, parapet walls and equipment stands are built from the same layers and take the most movement, so they split and pull away from the wall. Ponding adds to everything else, because standing water speeds up surface breakdown and sits against every lap and flashing long enough to find a way in.
Ballasted commercial roof with a rooftop unit, pipe stacks and a crane on the skyline
Installing and repairing built-up and modified bitumen: the inspection decides
A&M Roofing Services installs built-up roofs as part of its low-slope work and repairs and installs modified bitumen roofs, all from its base at 123 Tewksbury Street in Andover. Because the crews are also licensed installers for Carlisle, Firestone, Sika-Sarnafil, Johns Manville and Duro-Last, owners can compare a bitumen roof against single-ply on the same building and hear a straight answer about which one fits.
Whether to repair or replace comes from an on-roof inspection, not from a guess at the street. A&M's crews walk the roof and note drainage, roof traffic, weather damage and moisture infiltration. A roof with a few open laps and a tired flashing at one curb is a repair. A roof with wet insulation, widespread blistering or drains that cannot clear water needs a different conversation, and the inspection is what puts evidence behind it.
When a roof is installed, A&M's specially trained staff plan the job first, and the work is done to meet or exceed the manufacturer's specifications so it is covered by warranty. Every job is professionally planned and executed, which on a multi-ply roof means the plies, laps and flashings are built to the written details rather than to whatever the day allows.
Chapter 03
Keeping a bitumen roof working: debris, small repairs and a budget for what comes later
The cheapest year of a bitumen roof's life is the one where somebody clears the drains. A&M's maintenance packages include visual roof inspections of the membrane, flashings, sheet metal, drains and gutters, along with debris removal from drains, gutters, conductor heads and roof leaders, so water leaves the roof instead of waiting on it.
Small defects get repaired during the visit instead of being logged for later. A cracked flashing, an open lap or a patch of worn surfacing is a short repair when it is found early, and a ceiling stain when it is not. Survey documentation, meaning written reports, photo documentation and a roof plan, gives the owner a record of what was found and what was fixed.
The same packages include budgeting for major repairs or replacement, if it comes to that. A facility manager who can see the roof's condition on paper can plan capital spending a year ahead instead of reacting to a leak. If water is already coming in, emergency repair is available 24/7/365 at (978) 475-4500.
A&M Roofing Services is a licensed installer for Carlisle, Sika-Sarnafil, Firestone, Johns Manville and Duro-Last, and has roofed commercial buildings out of Andover since 1978.