Sizing and placing intake and exhaust vents properly for a slate roof is essential for maintaining good attic ventilation, which helps prevent moisture buildup and extends the life of the roof. Intake vents, usually installed along the eaves or soffits, bring fresh air into the attic, while exhaust vents near the ridge let warm, moist air escape. The general guideline is to provide 1 square foot of vent area for every 150 square feet of attic floor space, split evenly between intake and exhaust. However, for roofs with a vapor barrier or low permeable insulation, a 1:300 ratio can be acceptable. Because slate is a dense, fragile material, it’s crucial to place vents without compromising the surrounding tiles. Vents should not be installed in a way that causes uneven heating or any mechanical damage to the slate, so choose vent products specifically made or approved for slate roofing.
Before you install or adjust vents on a slate roof, check for obvious signs of poor ventilation: condensation on the underside of the roof sheathing, mold, or ice dams in winter. A safe DIY step is to ensure soffit vents are unobstructed and clean, and to look for attic temperature differences in summer by comparing attic and outdoor temperatures. Avoid stepping directly on slate tiles—stick to roof edges or use roof ladders to prevent cracking. When in doubt, call a roofer experienced with slate roofs to evaluate the vent strategy. Questions to ask your contractor include: “How will you ensure vents are placed without damaging or voiding my slate roofing warranty?” and “What vent types and sizes do you recommend for my specific attic layout and climate?” These ensure your ventilation upgrades protect your slate roof’s beauty and long-term function.