Slate & Cedar Roofing in Connecticut

Slate: the longest-lived roof in New England

Natural slate is stone, and a good slate roof can outlast the house’s owners several times over. The National Park Service’s guidance on historic slate roofs (Preservation Brief 29) makes a point every slate owner should know: the lifespan depends on the kind of slate, harder slates lasting far longer than soft ones, and on many old roofs it is the nails and the flashing that give out first, not the slate itself.

That is why a slate roof with leaks is not automatically a slate roof at the end of its life. Rusted nails let individual slates slip; a corroded valley or chimney flashing lets water in around perfectly sound stone. Both are repairs.

Repair is often the right answer

A broken or slipped slate is replaced with a matching one, held with a slate hook or a nail covered by a metal bib, without disturbing the slates around it. Flashing at chimneys, valleys and walls is replaced in copper or another long-lived metal so it lasts as long as the stone does. Done properly, that kind of repair buys decades.

One rule matters more than any other: slate should not be walked on by anyone who does not know how. The Park Service warns that foot traffic is one of the main causes of broken slates, and a well-meaning contractor walking a slate roof to inspect it can cause more damage than the leak did. We inspect slate from ladders, hooks and the ground, and from the attic.

When a slate roof does need replacing

Replacement is the answer when a large share of the slates are flaking, splitting along their layers, or crumbling at the nail holes — the signs of soft slate at the true end of its life — rather than when a few are broken. The code then sets the rules for the new roof:

• Slate is allowed only on a roof that rises at least 4 inches per foot (IRC R905.6.2).
• New roofing may never be laid over an existing slate roof; the slate comes off (R908.3.1.1).
• Slate needs an ice barrier at every eave like any other roof in Connecticut (R905.1.2). See ice dams.

Cedar shakes and shingles

Cedar shingles are sawn, smooth and uniform; cedar shakes are split, thicker and rougher. Both are covered by their own sections of the code (R905.7 and R905.8) and both need a roof with enough pitch to shed water and enough air underneath to dry.

The enemy of cedar in Connecticut is moisture, not age. A cedar roof under heavy tree cover, on the north side of a house, or laid without room to breathe grows moss, holds water and rots far sooner than one in the sun. Clearing debris from the keyways and valleys and keeping overhanging branches back does more for a cedar roof than any coating.

Historic districts in Connecticut

Connecticut law lets towns create local historic districts (Connecticut General Statutes section 7-147a and the sections that follow it), and inside one, a historic district commission can require a certificate of appropriateness before visible exterior changes — which can include swapping slate or cedar for something else. Check with your town before choosing a material. We will work to whatever the commission approves.

Where Connecticut’s slate came from

Most of the slate on New England roofs was quarried along the Vermont–New York border, in the stretch known as the Slate Valley, which produced greens, greys, purples, mottled stone and the red slate found nowhere else in the country, or in Pennsylvania, whose black slates are generally softer. Knowing what is on your roof matters: a replacement slate should match the original in colour, thickness and hardness, or the repair will stand out and weather differently. Reclaimed slate salvaged from other roofs is often the best match for an old roof.

Snow guards

Slate, like metal, is smooth enough that a winter’s snow can let go all at once and slide off in a single sheet — onto a walkway, a porch roof, a car, or the gutters, which it can tear straight off the house. Snow guards are small brackets spaced across the lower roof that hold the snow in place until it melts off gradually. On a slate or metal roof over a door or a path, they are worth having, and the right time to add them is while the roof is being worked on.

Switching to slate

Natural slate is several times heavier than asphalt shingles. Putting it on a house that was not built for it means checking that the rafters and deck can carry the load, and sometimes strengthening them first. That is one of the main reasons people choose synthetic slate when they want the look on a house that never had it.

Synthetic slate and shake

Where natural slate or cedar is out of reach on cost or weight, synthetic versions made from engineered polymers get close on looks at a fraction of the weight. We install DaVinci, among others. A synthetic roof does not need the heavy framing natural slate does, but it is still a different material: in a historic district, ask the commission first.

What a slate or cedar roof inspection covers

We look for slipped and broken slates and their pattern, the condition of the nails, every flashing at chimneys, valleys and walls, the state of the deck from the attic, and, on cedar, moss, cupping, splitting and rot. You get photographs and a written answer: what can be repaired, what it costs, and how long that repair should buy you. See roof repair and roof replacement.

Common questions about slate and cedar roofs