Roof substrate movement is a condition where the substrate, or roof deck in residential properties, expands and contracts. This causes the decking material to buckle or have gaps that can result in conditions that may require major roof repair. In this blog, we look at the causes of roof substrate movement.
What Causes Roof Substrate Movement?
Ever notice how concrete roads have gaps every few feet? The gaps are there to accommodate expansion and contraction from temperature changes. If the concrete blocks are installed too close to one another, it would result in cracks from the force of concrete blocks pressing against each other. Roof substrate movement is similar, except that the decking materials are more affected by moisture than temperature.
Plywood or oriented strand board (OSB) are two of the most-used materials for roof decking. It’s important for these materials to have and maintain balanced moisture content. Unlike concrete roads, leaving gaps to accommodate expansion and contraction is not ideal, as the gaps are where the fasteners will need to be installed. If the roof has skylights, vent pipes or other kinds of penetrations, these have to be accounted for as well.
Countering Roof Substrate Movement
Two things can happen when the roof substrate moves. A substrate with too much moisture will cause the outer layer of shingles to split as it dries. This leads to one or several cracks across the roof. Alternatively, if the substrate was installed in conditions that were too dry, the roof deck will buckle as the board edges push against each other. In either case, the results will likely be visible from the ground and could compromise the roof’s overall performance.
Professional roofers counter these problems by making sure the plywood or OSB is properly “adjusted” to the local humidity levels, since it typically leaves the factory dry. Proper attic ventilation, as well as waterproofing materials such as GAF’s Deck-Armor™ or Shingle-Mate®, can help minimize moisture intrusion and counter roof substrate movement.
To learn more about our roofing and gutter installation services, call The Thomas Roofing Company today at (410) 692-8998. You can also fill out our contact form to schedule a free, no-obligation quote. We serve many areas in Ellicott City and Columbia, MD.