Can You Put a Metal Roof Over Existing Shingles?

It is one of the first questions people ask, usually hoping the answer is yes, because stripping a roof is a meaningful part of the cost and all of the mess.

The answer is that it depends on the roof, and Highland does install over existing shingles where the structure allows it. What follows is what has to be true before that is a good idea.

What has to be true first

Going over shingles is a decision about the deck, not about the shingles. The questions are always the same.

• Is the deck sound? This is the whole thing. Soft, delaminated or rotten sheathing does not stop being rotten because there is a new roof over it, and you have now buried the problem under something designed to last fifty years.
• How many layers are already up there? Roofs that have been done twice already are a different conversation from roofs on their first covering.
• Can the structure take the load? Metal is light, which helps, but you are adding rather than replacing.
• What does the municipality say? Requirements vary, and this is worth confirming for your address rather than assuming.
• Is the existing surface flat enough? Curled, cupped or badly patched shingles telegraph through, and on a low-relief profile you will see it.

What you give up

The saving is real, but so is the trade-off, and the trade-off is information.

When the old roof comes off, the deck gets inspected board by board. That is the one moment in a roof's life when somebody can see the structure, find the previous repair that was never quite right, and deal with it while it is cheap. Leave the shingles on and you have chosen not to look.

You also inherit whatever is under there. If the old roof was leaking slowly somewhere, that moisture is now sealed in rather than dried out.

When stripping is the only honest answer

There are roofs where going over the top is simply the wrong call, and a roofer who agrees to it anyway is doing you no favours. Known leaks, visible sagging between rafters, any softness underfoot, or a roof that has already been layered more than once all point the same way.

The awkward truth is that the cheapest quote on your table is sometimes cheap because it proposes covering a problem rather than fixing one. That is worth asking about directly.

How to decide on your own roof

You cannot settle this from the ground, and neither can we. It needs someone in the attic looking at the underside of the deck, and someone on the roof looking at what is actually up there.

What helps us give you a useful answer early: how old the current roof is, whether it has been replaced before and how many times, whether you have ever had a leak or a stain on a ceiling, and whether anything about the roofline has ever looked uneven from the street.

If you are weighing this up, tell us about the roof and we will tell you honestly which of the two jobs you are actually looking at.