Can you put a new flat roof over an existing one?

Yes, if there is only one existing roof covering and it is dry and sound. Codes do not allow a recover over a water-soaked roof or over two existing layers.

How do I know if my flat roof insulation is wet?

Core cuts and a moisture survey, infrared or capacitance, across the whole roof. Soft spots and ponding are warning signs but not proof.

Is a roof recover cheaper than a tear-off?

Usually, because it skips removal and disposal, but only when the existing roof qualifies. Recovering over wet insulation costs more later.

How long does a flat roof last?

About 20 to 30 years for a properly installed EPDM or TPO membrane and 15 to 25 years for modified bitumen.

Can You Put a New Flat Roof Over the Old One?

Short answer: Sometimes, and only over one dry, sound roof. Building codes allow a recover over a single existing roof covering, but not when that roof is water-soaked or already has two layers. Before recommending one, a contractor should core the roof and survey it for wet insulation, check the deck, and confirm the structure can carry the extra layer. If any of that fails, a full tear-off is the right job.

When a recover makes sense

The existing roof is one layer, the insulation under it is dry, the deck is sound, drainage works, and the structure has capacity for the added weight. Then a new membrane over a cover board saves the tear-off, keeps the building weathertight during the work, and often finishes faster.

When it does not

Wet insulation. A recover buries the moisture, which keeps rotting the deck and rusting fasteners under the new roof. Wet areas must be cut out at minimum, and widespread saturation means tear-off.

Two layers already. Codes do not allow a third.

Deck or drainage problems. Ponding, a deflected deck or failed drains are not fixed by another layer; they are hidden by it.

How to find out

Ask for core cuts, which show how many layers there are and whether the insulation is wet, and for a moisture survey (infrared or capacitance) across the whole roof, not a walk-around. A recover recommended without either is a guess.

How we handle commercial roofs

We survey, core and photograph before we recommend recover or replacement, and price TPO, EPDM and modified bitumen systems for property managers, HOAs, churches and owners across Maryland and Northern Virginia.

MHIC #111971 in Maryland, Virginia Class A #2705183185, family-owned since 2005.

Get it looked at, free

We inspect across Maryland — Montgomery, Prince George's, Howard, Anne Arundel, Frederick, Carroll and Baltimore counties. Free inspection, photo report within 24 hours, and the report is yours to keep whether or not you hire us.