Flat roofs have a specific set of challenges when it comes to repairing or replacing them. Unlike a pitched roof, shingles and most metals and tiles aren’t viable. It has been done, but they’re not made for these types of roofs, and it doesn’t work out well most of the time. This leaves people with flat roofs two basic options, a built-up roof (BUR), or one of the membrane approaches brought about by more modern sciences.
The question is, with the cost of some options, and the difficulty of removing others, which is going to be more viable and cost-effective when the time comes? Should you replace or repair a commercial flat roof?
Today, we’re going to go over a brief refresher of how flat roof materials work, the symptoms of a roof needing attention, and the pros and cons of replacing versus repairing. It’s a different beast than sloped or pitched roofs. The same problems do happen, but for different reasons.
Built-Up Roof (BUR)
BUR is the oldest way to do a flat roof short of exposed adobe or wood. It’s been around since the Victorian era at least, though it’s arguable that an ancestral form of it has existed much longer, with tarred roofs.
It’s built by introducing layers of tar/asphalt, fiber (often fiberglass, though felt originally). It is topped with crushed stone, river rock, artificial mulch, lava rock, or crushed shell. Modernly, it usually comes in rolls of pre-sandwiched asphalt and fiberglass or felt. It’s either applied with heat, a chemical activator, or via self-adhesion, heat being the oldest and most common way to do it.
Membrane roofs vary pretty wildly in chemical composition, the most common being a polyvinyl chloride base (PVC or vinyl), though several other synthetics of similar nature also exist. These are more or less a solid singular sheet of material, usually self-adhesive though some use an applied “cement.”
Often, these are topped with loose gravel or something similar for aesthetic and extra protection, though some advise against this. Membrane roofs are newer, they do theoretically last longer, and they can be easier to install in some cases. They’re costlier though, more difficult to repair, and a real hassle to take off if you want to install a new roof from the ground up.
So, when do you need to address your flat roof? First and foremost, it’s always a good idea to have your roof checked out semiannually if you can, just to be safe. You can often catch problems before they can get terribly out of hand and minimize the scope of repair, and thus the cost. For commercial structures, inspections like this happen more often by law in most places. Sometimes, however, problems can be missed, or problems can spring up right after an inspection – this happens all the time.
Below are some common symptoms of potential roof problems.
Your Roof is Old
If you have BUR, your roof may be too old after about 50 years, sometimes less. For membrane, it could be 25-100 years (membrane hasn’t entirely hit the point where it’s aging that much quite yet). When a roof gets old, the seals break down, and it just becomes bad at doing its job, leading to other problems on this list.
If your roof is nearing or past its expected lifespan, it’s time to replace it.
You Have Leaks
Water damage is no joke. It can cause mold, decaying sheetrock, rusted or rotted infrastructure, electrical fires, and much more. A leak is a sign of punctures or compromised seams, flashing or sealing on your roof, which at the very least means you need to do repairs.
Leaks will spread and multiply with time, and molds can achieve toxic levels before you notice them. Do note that, especially in a commercial location, black mold is a serious problem. It can be incredibly dangerous to children, the elderly, and the infirm. It can even cause lasting health problems in healthy adults.
Your Energy Bills are High
Leaks don’t just come in the form of invading water. Air can escape through compromised seams, decayed insulation, and the like as well. This means you’re letting the heat out in winter and letting the air conditioning out in summer. You’ll notice this if your bills have been higher for no apparent reason.
Visible damage should be spotted in inspections, but if it’s a recent problem, maybe not. Visible damage on a flat roof tends to take the form of seams coming apart, flashing undoing itself, or blisters forming under the sheets of material.
If the roof isn’t particularly old, and this kind of damage is caught quickly, you can usually repair it.
Tear-Away vs. Roofing Over
Before you assume that a roof replacement is just too much, and you want to patch a bad roof that shouldn’t be patched, let’s point out that there are two types of roof replacement. Tear-away, or tear-off, roofs are where the existing roof is torn down to brass tacks, and a new roof built up.
This process is a challenge with a lot of flat roofs. The adhered membrane or asphalt layers have to be torn up, and it’s a lot of work, sometimes requiring reheating to make it malleable enough to achieve. That said, this is the more expensive solution to roof replacement, be it flat or sloped.
The other solution is to patch the seal issues and so forth on the existing layer, do necessary repairs to blisters, and then lay over a new layer of membrane or BUR sheeting. When it comes to membrane, this isn’t as tried and true as with BUR. Roofing over has its limits, and you are, ultimately, just prolonging a tear-away someone will someday have to do.
Repair or Replace?
How bad is the damage, and how old is the roof? If it’s not past its expected lifespan or very close to it, and the damage is manageable, you can repair it. Membrane, and even more so with BUR, are easy materials to repair compared to some sloped roof shingle styles. It generally involves cutting blisters and reapplying adhesive and caulk. Opening seams need more tar and sealant on them, and flashing can be replaced easily enough.
So, if the damage seems localized, and your roofing professional suggests repairing it, do so. But, if it’s old, bite the bullet and replace it. If the damage is really bad and spreading, bite the bullet, and replace it.
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