A commercial roof is bought once and lived with for two decades, usually by someone who inherited the decision from whoever signed the contract. The bids arrive looking similar, the square footage matches, the membrane brand is familiar, and the cheapest number wins.
The difference between those bids is rarely the membrane. It sits in the warranty language, in whether the old roof comes off, and in what happens on the building after year one.
The Warranty Offered Is Rarely the Warranty Assumed
“Twenty-year warranty” means almost nothing on its own. There are three very different products behind that phrase.
A material-only warranty replaces defective material and nothing else. Labour, tear-off, disposal and reinstallation stay with the building owner, which on a failed roof is most of the cost. A system warranty covers materials and the labour to repair them, usually runs fifteen to twenty years, and often carries a dollar cap tied to the original material cost. A No Dollar Limit warranty removes the cap entirely, with no proration as the roof ages.
Manufacturers do not hand out NDL coverage on request. It requires installation by a contractor certified by that specific manufacturer, a specified combination of products, and usually a final inspection by a manufacturer’s representative before the warranty is issued at all.
Read that again, because it decides the shortlist. The strongest coverage available on a roof is simply unavailable through an uncertified installer, no matter how good the price looks or how long they have been in business.
So the shortlist for commercial roofing in Denver, CO narrows itself: ask each bidder which manufacturers have certified them, for which systems, and verify it with the manufacturer rather than the salesperson. If a bidder cannot get an NDL warranty issued on the building, that answer is worth hearing before the contract is signed.
Tear-Off Versus Recover Is a Code Question
Owners often assume leaving the old roof in place is a budget decision. The building code frequently removes the choice.
A recover is not permitted where the existing roof already carries two or more applications of any type of roof covering. It is also barred where the existing roof is water soaked or deteriorated enough that it cannot serve as a base, and where the existing covering is slate, clay, cement or asbestos-cement tile. In those cases the work becomes a roof replacement, which by definition means removing every existing layer down to the deck.
There is a cost consequence that surprises people. Once above-deck insulation is removed during a replacement, what goes back has to meet current energy code R-values rather than whatever was acceptable when the building went up. A bid that quietly assumes a recover, on a roof that cannot legally take one, is not cheaper. It is incomplete.
Ask any bidder how many layers are up there now and how they confirmed it. Test cuts are the honest answer.
If Tile Is on the Table, the Structure Decides First
Tile is durable, handsome and extremely heavy, and weight is where the conversation has to start.
Concrete tile commonly runs 900 to 1,200 pounds per square, meaning per 100 square feet of roof. Clay usually falls between 600 and 1,000. Asphalt shingles sit around 225 to 350. On a building framed for shingles, switching to tile can add tens of thousands of pounds of dead load, which is a structural engineering question rather than a roofing one.
Concrete carries a second issue that rarely appears on a spec sheet: it absorbs a meaningful share of its own weight in water, so a soaked roof temporarily weighs more than the dry figure suggests.
None of this rules tile out, and buildings framed for it perform beautifully for decades. It does mean the order of operations is fixed. Anyone considering tile roofing in Denver should get the framing assessed before choosing a profile or a colour, because that assessment is the only step that cannot be corrected afterwards. A contractor who raises load capacity in the first conversation has done this before.
What Keeps the Warranty Alive After Year One
Most manufacturers require at least one documented professional inspection every year, and inspecting twice, spring and autumn, is the practical standard.
The bigger risk is other trades. An HVAC contractor cutting a new curb, a telecoms crew running conduit, a window cleaner anchoring to a parapet: any of these can create an unapproved penetration, and when a leak appears nearby, the manufacturer’s inspector finds it. Coverage disappears at that point, and no one remembers who made the cut.
The fix is a rule, not a product. Nobody touches the roof without the certified contractor being called first, and every visit gets documented. Worth asking at signing: is the warranty transferable if the building sells, and does the coverage prorate over time.
Questions That Separate the Bids
Which manufacturers have certified this contractor, and does the certification cover the exact system being quoted. Who performs the completion inspection, and is it a manufacturer representative. What is specifically excluded, particularly around ponding water and wind events. How many roof layers exist now, and how was that verified.
Answers to those five reveal more than any reference list will.
Conclusion: The Cheapest Bid Is Usually the Least Specific
A roofing proposal that names the warranty tier, states the tear-off scope, and explains how the deck was assessed is doing the buyer a favour, even when the number is higher than the one beside it.
Owners weighing options can put those questions to any contractor, including firms like Elite Construction, which handles commercial and specialty roofing alongside windows, doors and painting. A bidder who answers them clearly has thought about year fifteen. A bidder who cannot is quoting a price, not a roof.