Oil canning in synthetic slate roofing refers to the visible waviness or uneven surface that can appear on the roof panels. This effect is usually caused by variations in the panel installation process or the materials themselves, such as uneven fastening, thermal expansion, or the substrate beneath the roof not being perfectly flat. Synthetic slate is a durable and lightweight alternative to natural slate, but because it’s often made from flexible materials, it can show these ripples more noticeably when the panels aren’t secured evenly. It’s also more prone to oil canning on larger, flat roof sections or on warm sunny days when the material expands. Homeowners might first notice this as a kind of distorted look on what should be a smooth finish, especially under sunlight.
For simple diagnostics, start by visually checking your roof on a sunny day and note any panels that look uneven compared to surrounding ones. From an accessible level, you can gently inspect if panels are tightly fastened without obvious warping or soft spots. Avoid walking extensively on the roof to prevent damage. If you spot noticeable oil canning, it’s best to call a professional roofer to evaluate whether panels can be re-fastened, if underlying decking needs adjustment, or if specific clips or fasteners must be replaced. When talking to a contractor, ask how they address oil canning during installation and what warranty covers this issue. Also, inquire if they use specific fastening techniques or materials designed to minimize these waves, ensuring your synthetic slate roof stays visually consistent and structurally sound over time.