Roof recover (roof-over) explained

A roof recover installs a new roof covering over the existing one without tearing it off. On a house, that usually means new shingles over one existing layer. On a commercial roof, it usually means a new membrane over the old one, often with a layer of cover board or insulation between them.

Recover, coating and replacement compared

	Coating (restoration)	Recover	Replacement
Existing roof stays?	Yes, and it stays the waterproofing layer, renewed with a fluid-applied coat	Yes, but a new roof system goes on top	No, removed down to the deck
New membrane or shingles?	No	Yes	Yes
Wet insulation addressed?	Must be removed first	Must be removed first	Removed with the tear-off
Deck visible for inspection?	No	No	Yes
Typical code questions	Manufacturer and warranty rules	Number of existing layers, condition, weight	Full current requirements, often including insulation

When codes limit a recover

Model building codes generally do not allow a new roof covering over an existing one when:

• The existing roof has two or more layers already.
• The existing roof or deck is water-soaked or deteriorated enough that it is not an adequate base.
• The existing covering is slate, clay or cement tile, or asbestos-cement tile.

Your city or county adopts a specific code edition and may amend it. The building official decides what is allowed on your building.

Energy code and recovers

For commercial roofs, the energy code often treats a recover differently from a full replacement. Under the 2021 IECC, as explained in a municipal handout we reviewed from Illinois, a recover over an existing roof may not trigger the full above-deck insulation requirement that a replacement does. Ohio and Michigan have adopted their own versions of the energy code. Confirm locally before assuming an exemption.

Before choosing a recover

1. Get a moisture survey. Wet insulation left under a recover keeps causing damage.
2. Confirm the number of existing layers.
3. Check the deck where you can, and the structure’s capacity for the added weight.
4. Confirm the new system’s warranty allows installation over the existing roof.
5. Confirm drainage will work at the new roof height, including at edges, curbs and doors.

Recover is a design decision, not a shortcut. The coating feasibility check and the commercial inspection intake help organize the facts a professional will need.

Moisture survey basics

A moisture survey tells you where the insulation under the roof is wet. Common methods:

• Infrared thermography: a scan after a sunny day shows wet areas holding heat after dark.
• Capacitance or impedance meters: a grid of readings across the roof.
• Nuclear moisture gauges: readings on a grid that detect hydrogen in water.
• Core cuts: small samples that confirm what the scan found.

Wet areas are removed and replaced before any recover or coating. If a large share of the roof is wet, replacement is usually the better investment. Our coating feasibility check and replace or recover planner walk through the decision, and the commercial roof cost planner puts ranges next to each path.

Run your numbers