Slate roofs

Natural slate is quarried stone split into thin sheets. In Colorado it's mostly found on older homes in historic neighborhoods, and occasionally on high-end new builds. A well-made slate roof can last generations, but only if the people working on it know what they're doing.

How long slate lasts

InterNACHI's guideline range for slate is 60 to 150 years, the widest of any common material. The range reflects differences in stone quality: some slate weathers slowly for a century or more, some flakes and softens sooner. As with any roof, severe weather can shorten that.

The stone is often not the first thing to go. Nails corrode, and flashing at chimneys and valleys wears out. As a general rule, a slate roof that leaks usually needs those parts fixed, not new slate.

Weight and structure

Slate is heavy, far heavier than asphalt shingles, though exact weight varies with thickness and we don't cite a figure here. Homes built for slate have framing sized for it. Putting slate on a home originally built for shingles calls for an engineer's review, especially at higher elevations where Colorado snow loads are larger. See Colorado's climate for how snow loads rise with elevation.

Hail and slate

Slate is hard, but it's brittle. Large hail can crack or break slates, and thinner slates are more vulnerable. Broken pieces in gutters or on the ground after a storm are a sign to have it checked. The free Roof Report shows how much large hail has fallen near you. Insurance claims on slate can be complicated by matching old stone, which is a policy question; our insurance guide explains how matching works in Colorado.

Finding a specialist

Slate is a specialty trade. Installing and repairing it uses different tools and methods than shingles, including slate hammers, rippers and copper nails or hooks. Many general roofing crews don't do it.

• Ask how many slate roofs the contractor has installed or repaired, and ask for addresses or photos.
• Ask how they'll move around on the roof without breaking slates, such as with ladders hooked over the ridge or staging.
• Ask where they'll source matching slate.
• Be cautious of anyone who recommends full replacement without explaining why repair won't work.

Our hiring guide covers licensing, contracts and insurance checks that apply to any roofer.

How slate gets repaired

A single broken slate can usually be replaced without disturbing its neighbors. A roofer cuts the old nails with a slate ripper, slides in a new slate and secures it, often with a metal hook or strap. Done well, the repair is nearly invisible.

Walking on slate breaks it, so repairs should be done by someone who knows how to work from ladders or staging. Don't let other trades walk on a slate roof. If you live in a Denver historic district, a roofing design review may also apply to work that changes the roof's appearance.

Compare slate with lighter look-alikes on the synthetic slate page, or see all options on the materials overview.

Common questions

How long does a slate roof last?

InterNACHI's guideline range is 60 to 150 years for natural slate. The flashing and fasteners often wear out before the stone does.

Can a regular roofer fix my slate roof?

Many asphalt crews don't work on slate. Ask specifically for slate experience and examples of slate repairs, because the techniques and tools are different.

Is it worth repairing an old slate roof?

Often, yes. If the slates are sound and only some are broken or the flashing has failed, repairs usually cost far less than replacement. A slate specialist can assess it.

Will hail damage slate?

It can. Slate is hard but brittle, so large hail can crack or break individual slates. Damaged slates can usually be replaced one at a time.