Commercial Roofing in Mill Valley, CA

What Commercial Roofing Covers on a Low-Slope Building

Commercial roofing keeps flat and low-slope assemblies watertight on offices, retail shells, and multi-tenant properties. Membrane, seams, drainage, and the roof deck matter more here than shingle color. A crew that only hangs asphalt shingle is not equipped for this trade.

We begin with a roof asset survey: core cuts, moisture readings, and a slope check. That tells us whether the assembly can be refit, recoated, or has to come off entirely.

Low-slope systems we install

• TPO membrane is a heat-welded single-ply sheet that reflects sunlight and handles heavy rooftop equipment on restaurants and warehouses.
• EPDM is a rubber membrane with a long record against UV exposure and ponding water, and it flexes with an older roof deck.
• Modified bitumen is an asphalt-based cap sheet applied self-adhered or torched, and it is often the right match when we replace a built-up roof.
• PVC membrane resists kitchen grease and chemical exhaust, which is why it belongs over commercial kitchens.
• Built-up roof, or BUR, alternates roofing felt and bitumen in layers for buildings that want weight and redundancy.
• Standing-seam metal panel suits steeper commercial sections where a single-ply sheet would not shed water fast enough.
• Acrylic and silicone coating restores a sound modified bitumen or metal roof when the assembly still has life left in it.

Carlisle SynTec, GAF EverGuard, Firestone, Johns Manville, and Versico all make TPO and EPDM sheet we can spec. What decides performance is thickness, attachment, and the details at the edge.

Insulation, Parapet Detailing, and Ventilation

Insulation does two jobs here. It cuts cooling load, and it gives the membrane a flat surface to bond to. Wet insulation is the most common reason a commercial roof fails early, because water wicks sideways through the board and never shows on top.

Parapet walls need counter-flashing and coping that push water toward the drain. Without them, water seeps behind the membrane and rots the wood blocking at the wall base.

Ventilation matters too. Ridge vent, soffit vent, or an attic fan keeps the roof deck dry, so the substrate under the membrane does not decay from trapped moisture.

Components We Check on Every Commercial Roof

Most leaks land at a penetration or a transition, not in the middle of the field. These are the pieces we inspect, reseal, and repair before we quote anything.

• Step flashing, counter-flashing, and apron flashing seal where the roof meets a wall, while chimney flashing, pipe flashing, pipe boot, and vent boot handle the penetrations that leak first.
• Drip edge, eave, soffit, fascia, and rake protect the roof edge, which is where wind uplift starts and where salt air corrodes fasteners.
• Ridge cap, ridge vent, hip, and valley details control how water and air move across the roofline, which matters more on a gable than on a flat deck.
• Gutter and downspout runs carry runoff away, and a clogged scupper or blocked coping drain can back water under the membrane inside one storm.
• Sealant, caulk, mastic, and roof cement close small gaps, but they are a stopgap. A new flashing bead or a torched patch holds far longer.
• Vapor barrier, underlayment, synthetic underlayment, and ice-and-water shield sit under the finish layer to stop an ice dam from forcing water up the eave.
• Skylight, dormer, canopy, awning, and overhang all create transitions that need weatherproofing and real waterproofing detail, not just adhesive.
• Snow guard and anchor points keep snow from sliding and give our crew a safe tie-off on a mansard or gambrel section.
• Truss, rafter, joist, ridge beam, and purlin carry the load, while batten and counterbatten set the spacing under a metal panel roof.
• Plywood, OSB, and sheathing form the roof deck and the substrate for everything above. Rot, decay, or sag there means the decking comes out.
• Shingle, three-tab shingle, and architectural shingle held with ring-shank nails show up on the residential and mixed-use buildings we also service, along with wood shake, cedar shake, slate, clay tile, and concrete tile.
• Corrugated panel, tar paper, felt, tar, pitch, asphalt, and bitumen are legacy materials we still find, and a roof estimate has to account for removing them safely.

On shingle sections we set a starter course along the eave, run the field course straight up the rake, and keep staggered courses aligned so the exposure stays even.

Tools tell you who actually showed up: ladder, scaffold, and safety harness for access, roofing square for layout, an air compressor and nail gun for fasteners, a pry bar and roofing shovel for the tear-off, and a torch or roller for membrane work. We hand-check every nail and screw so nothing gets overdriven.

We stage a dumpster for debris in the lot and haul it out daily. A roofing contractor who leaves debris overnight is telling you something about how the job is run.

What the Local Climate Does to a Commercial Roof

Coastal fog and morning moisture keep a low-slope roof damp for hours after sunrise, which is exactly when seams begin to fail. Winter atmospheric rivers drop a season of rain in days, so drainage matters more than membrane thickness in February.

• High UV exposure erodes asphalt-based cap sheets faster than inland, so granule loss and alligatoring appear earlier than owners expect.
• Salt spray in the air corrodes metal flashings and fasteners, especially at the roofline and on buildings closer to the water.
• Wildfire smoke residue needs gentle cleaning rather than a pressure washer, which can strip a coating and open the seams underneath.

How We Tell Repair From Replacement

Not every wet roof needs a tear-off. When less than roughly a quarter of the surface is affected and the deck is sound, a targeted repair and a fresh coating will buy years. Past that point, patching becomes a cycle of returns.

• Granule loss and alligatoring on a modified bitumen cap sheet mean the surface is eroding and the bitumen below is oxidizing.
• Blisters, wrinkles, and delamination point to trapped moisture, where the membrane has peeled off the substrate and will keep tearing at the seams.
• Ponding water, cracking, and membrane splits trace back to inadequate slope or a clogged drain, and they will not fix themselves.
• Wet insulation found in core cuts, plus rot or decay in the deck, pushes the job toward full replacement.
• Corroded fasteners, exposed fastener heads, and spalling or flaking metal at the roofline show what salt air and UV degradation do over time.
• End-of-life wear arrives all at once on older systems, and a deck that begins to settle or sag flattens the slope so water stops moving.
• Interior water stains near roof edges, or a steady drip after rain, usually mean the leak sits at a flashing rather than overhead.

What Commercial Roofing Costs in Mill Valley

A recover, or overlay, costs less than a tear-off because you skip the dumpster haul and most deck repair. Once we open the roof, we know which one you actually need.

• Recover over a sound existing membrane: roughly $4 to $7 per square foot.
• Full tear-off with new insulation and TPO or EPDM: roughly $9 to $16 per square foot.
• Modified bitumen cap sheet replacement: roughly $7 to $12 per square foot.
• Targeted roof repair, flashing rebuilds, and coating: priced by the line item, typically a few hundred to a few thousand dollars.

Those are ranges, not quotes. Slope, access, tenant hours, and how much wet insulation comes out move the number more than anything else does.

Building Code, Permits, and Insurance Claims

California Building Code Chapter 15 requires roof coverings to meet a Class A or B fire classification, and structural additions or reroofs over 5,000 square feet usually need an engineered permit under CBC 1504. Title 24 also sets cool-roof reflectance values for low-slope commercial roofs.

We pull the permit and keep the inspection record, so a future buyer or insurer can find it. When storm damage is involved, we document the storm date, photograph the failure, and meet your adjuster on the rooftop.

Insurance claim assistance here means a line-item estimate that mirrors the adjuster's scope, supplemental claims when hidden damage shows up, and help with the proof of loss form before your claim deadline.

Warranty, Maintenance, and What Comes After the Install

Warranties on low-slope commercial systems run 15 to 30 years NDL, depending on membrane and attachment method. Maintenance keeps them valid, since most manufacturers want documented roof inspections and prompt repairs on record.

We recommend two visits a year: once after the winter rains, once before summer. We clear drains, reseal seams, recaulk flashings, and log the condition of every penetration with photos.

We renovate and maintain roofs across the county, and we will tell you plainly when the honest answer is to mend a small problem instead of selling you a new roof.

Questions we hear on almost every job

How long does a commercial roof replacement take? Most low-slope roofs run two to five days of field work, plus cure and inspection time. Tenant coordination, weather, and wet insulation removal stretch that window.

Can you work around our business hours? Yes. We phase the work by rooftop section and schedule the loud operations before you open or after you close.

Do you handle residential roofing too? We do, including shingle roofing, metal roofing, shingle repair, gutter installation, gutter repair, roof maintenance, and skylight installation for homes in the area.