If your commercial building or older flat-roof structure still has a tar and gravel roof, you're probably starting to think about replacement options. These roofs were once standard across the South — especially here in Alabama — but times have changed. Materials have improved, building codes have evolved, and your options are now better than ever.
At Birmingham Roofs, we’re often asked: What’s the best way to replace a tar and gravel roof? And more importantly, Can you install a new roof system over the old one?
Let’s break it down.
Why Replace a Tar and Gravel Roof?
Tar and gravel roofs — also called built-up roofing (BUR) systems — were common for decades. They’re made up of multiple layers of asphalt and felt, topped with gravel for UV protection and fire resistance. But over time, they:
Get heavy and brittle
Trap moisture under the gravel
Become difficult to patch or diagnose leaks
Aren’t as energy-efficient as modern materials
And when it’s time for replacement, the question becomes: Do we have to tear the whole thing off?
Can You Install a Roof Over Tar and Gravel?
Yes — but only if there's one layer.
In Alabama, state building code only allows one roof overlay. If your tar and gravel roof is the original system and there's nothing else stacked on top, we can usually build over it using modern materials like TPO (thermoplastic polyolefin). But if there’s more than one existing layer, at least one of them will legally need to be removed before we install anything new.
This is where a roofing expert (like us) comes in to inspect your system and determine the best path forward.
The Replacement Process: From Tar & Gravel to TPO
When there’s only one layer of existing roofing, we can typically move forward without a full tear-off. Here’s how that usually looks:
1. Inspection and Moisture Scan
We first inspect your existing roof and often perform a moisture scan to make sure the system is dry enough to build over.
2. Insulation Installation
Next, we install a layer of high-performance insulation. This might be ISO board, tapered polyiso for drainage, or other rigid insulation. We screw the insulation directly through the old roofing and into the decking below to create a solid, secure base.
3. TPO Membrane Installation
Finally, we mechanically fasten a new TPO membrane on top of the insulation. This creates a watertight, energy-efficient, and code-compliant roofing system that’s designed to last 20+ years with proper maintenance.
What If There Are Multiple Layers?
If your tar and gravel roof already has a second roofing system laid over it (which is common in older buildings), Alabama law requires us to tear off at least one layer before proceeding.
In those cases, we’ll:
Remove the top layer(s)
Inspect the decking underneath
Install new insulation
Mechanically fasten the TPO system from scratch
The process takes a bit longer and may cost more up front — but it ensures your roof meets all state and city building codes and performs reliably for years to come.
Why TPO Is the Go-To Replacement Material
We recommend TPO for most flat roof replacements in Alabama because it’s:
UV resistant: Helps reflect heat and reduce cooling bills
Durable: Holds up to Alabama’s heat, storms, and even occasional hail
Cost-effective: One of the most budget-friendly commercial roofing options
Energy efficient: Helps improve your building’s insulation performance
TPO also installs cleanly over most existing systems and is a smart long-term upgrade from old tar and gravel roofs.
Call Birmingham Roofs for Expert Flat Roof Replacement in Alabama
Replacing a tar and gravel roof might sound like a big job, but it’s one we’ve done many times all across the state — from Birmingham to Tuscaloosa to Gadsden and everywhere in between. Whether you have a small office building, warehouse, or large commercial facility, Birmingham Roofs can guide you through your options and deliver a clean, code-compliant install.
We’ll inspect your roof, check the number of layers, and walk you through the best insulation and membrane systems for your building and budget.
Ready for a Free Estimate?
Call Birmingham Roofs today or fill out our quick form to schedule a free inspection. Let’s replace that tar and gravel roof the right way — the Birmingham Roofs way.
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