Can New Shingles Be Installed Over Old Ones?

It’s a question we hear all the time around Tacoma: “Can’t you just put the new shingles over the old ones?” Technically, yes — Washington building codes allow it in most cases. But just because you can doesn’t always mean you should.

At Robb’s Roofing, we’ve worked on hundreds of roofs where that second layer ended up causing more problems than it solved. It might seem like a shortcut to save time or money, but covering old shingles often hides damage that needs to be fixed first.

Why Roofers Sometimes Install Over Old Shingles

The idea makes sense at first. Laying new shingles over the old ones skips the tear-off step, which means:

• Less mess — no piles of torn-off shingles in the yard.
• Less labor cost — the job goes faster.
• Immediate coverage — a new look without full removal.

But that’s where the benefits end. The real cost of a “roof-over” usually shows up a few years later — sagging spots, trapped moisture, or hidden rot that slowly spreads underneath.

What Can Go Wrong

When you add another layer of shingles, you’re adding hundreds of extra pounds to your roof. Older roofs in Tacoma — especially ones exposed to years of rain and moisture — may not handle that weight well.

Here’s what we often find under double-layered roofs:

• Soft or sagging decking that can’t support extra shingles.
• Trapped moisture that never fully dries between layers.
• Hidden leaks or rot that grow quietly until major damage appears.

By skipping the tear-off, you also miss the chance to inspect what’s underneath — the flashing, decking, and underlayment that keep everything watertight.

Quick Guide

Quick answer: It’s allowed in Washington, but not recommended — it adds weight and hides damage.

Try this: Tear off the old shingles for a full inspection whenever possible.

Stop signs: A sagging roof deck or an existing double layer means no more should be added.

Typical cost: A tear-off adds about $1,500–$3,000, but it protects your home long-term.

Tacoma’s Weather Makes Tear-Offs Worth It

With Tacoma’s long rainy seasons, roofs take on a lot of moisture year after year. Any water trapped under that first layer can cause rot or mold if another layer is added on top. The damp climate here also makes it harder for the layers to dry out, which shortens the life of both sets of shingles.

Starting fresh lets us fix any soft wood, reseal flashing, and make sure the roof can breathe properly. It costs a little more up front, but it saves you from paying for major structural repairs down the road.

How Robb’s Roofing Handles It

When we inspect a roof, we check the structure, attic ventilation, and decking before recommending anything. If the roof’s still solid and code allows it, we’ll explain your options clearly — no pressure either way. But in most Tacoma homes, a full tear-off is the smarter, longer-lasting choice.

Call Robb’s Roofing at (253) 820-2163 for an honest roof inspection. We’ll help you decide what’s best for your home — and make sure your new roof is built to last through every storm Tacoma throws at it.