Q: How long will slate last?

A: Softer, grayer slates may provide only 50 years of service, while darker and harder slate may last up to 400 years. Longevity cannot be determined at the time of quarrying. ASTM distinguishes between S1, S2, and S3 slate. NIST (National Institute of Standards and Testing) has identified strength and absorption criteria.

Q: Why grout a slate roof?

A: The main reason to grout a slate roof is to preserve its integrity and to protect the roof from deterioration. As a slate roof ages, finding professional help to provide what usually becomes annual maintenance becomes increasingly difficult. Unskilled mechanics attempting to repair a slate roof almost always cause more damage than they repair. Grouting a slate roof changes its nature entirely. A grouted slate roof is no longer a kinetic roof system dependent on multiple pieces to shed water, but becomes a monolithic roof system consisting of the original slate tiles and newly injected slate grout.

Q: Is all slate the same?

A: No. Slate varies widely for unexplained reasons. It can be black, gray, purple, blue, green, or red. It may be a solid color or streaked . Some slate changes color with exposure to weather. Some slate has ribbons of softer material that will deteriorate much faster than the rest of the slate.

Q: What about flashing details?

A: Slate Savers has a full line of products designed to address a variety of construction details, including some unique innovations intended to handle the most difficult flashing problems.

Q: What about condensation problems?

A: The voids in the roof system are a result of the nature of slate and never become a factor in ventilation. As is the case with any roofing system, if humidity and potential condensation merit concern, then sub-roof ventilation should be a design priority. Slate Savers has a proprietary approach called Slate Savers Vent-a-Ridge.

Q: Can thermal stress cause problems?

A: Slate Savers slate grout is specifically designed to accommodate the effects of violent shifts that can occur during certain weather events.

Q: What is reverse condensation?

A: Condensation which occurs in summertime conditions is called reverse condensation. The vapor flow is reversed and travels from outside to inside. In a slate roof numerous voids exist where vapor can accumulate, creating pockets of moisture that can weaken the underlying structure over time.

Q: Does grouting a slate roof create a water dam?

A: No. Water dams are created in kinetic roof systems such as slate roofs when a repair is made with non-compatible materials like roof cement or caulk. It refers to the inability of water within the system to be turned back out of the system. Water damming is a non-issue in a grouted slate roof, because the grouted slate roof is static. Referring to slate grout as a water dam is analogous to calling the asphalt in a Built-Up-Roof or the lap cement in a Single-Ply-Roof a water dam.

Q: Why does grouting work and how does it change a kinetic slate roof to a static system?

A: Imagine a (3/16”) thick rubber gasket approx. (¾”) wide that perfectly fits between two pieces of slate. Now imagine this gasket sliding under every exposed edge of slate and further imagine gluing it on both sides. This is what is achieved through slate grouting.


Phone: (717) 993-3990 / Toll Free: 877-SL8-SAVE (877-758-7283)