Garage: Green Roof and Exterior Stairs

The last two features of the garage, the green roof and exterior stairs, were finished after the fine details of the interior. Not the way a job would normally roll, but the timeline got out of sync because of weather delays.

When the garage project was replanned, a green roof was chosen for environmental, aesthetic, and practical reasons. The environmental factors include reduced water run of and improved energy efficiency. Aesthetically, a shed roof would have looked odd against the back of the house and a green roof would replace some of the mountain flora we excavated. And finally, any other type of roof would have impeded the rear bedroom’s egress window and thus eliminating a legal bedroom from the house.

The green roof begins with a flat roof: 5% pitch (1 inch drop per 4 feet of run). The truss system was designed to hold 40 pounds dead weight (roof decking, membrane, soil, plants) and 60 pounds live weight (snow) per square foot. The dead weight limits determine the depth of soil, and in this instance, the green roof matrix was able to be spread to a depth of 3 inches. This depth is enough to support sedum, and perhaps a few wildflowers will be able to survive.

Between the roof membrane and soil is a drainage/filtration system. The filtration system allows water to pass through into the drainage layer and the retention of the soil matrix. The drainage system is essentially a layer of connected plastic nubs that create channels for water to move off of the roof (water is heavy, water sitting on a green roof only pushes the live weight closer to capacity). This roof is a continuous, extensive green roof. This link provides a good explanation.

The roof matrix (soil) was carried up in buckets ahead of a November snow storm. The rush was on because once the roof was covered with snow, it would be difficult to find another opportunity until Fake Spring 1 (usually mid February) to finish the roof. Fortunately, unsaturated green roof matrix is light weight. Wild flower seed were spread over a quarter of the roof after the soil was in place. The best time is to spread seeds in the fall – overwintering helps the germination process.

So, the exterior stairs. Not part of the original plan, but a solution that was necessary because of the problem created by good news from the soils engineer. The soils engineer declared our cut into the hillside stable, which meant no retaining wall was needed. Much rejoicing followed because this was a significant savings. But the problem with this was discovered when it was time to back fill.

The retaining wall was supposed to connect with the side of the garage and hold back the backfill. Without the retaining wall, it became a question of how to hold back the soil. Fortunately, excavator Dave had a solution – stone steps along the side of the of the garage. Not only did the solution solve the issue with backfill stabilization, but provided a way to access the yard from the garage without having to go through or around the house.

Steps were ordered from Lyons Sandstone and were installed. It was an interesting process that relied on a pulley and Excavator Dave’s knowledge of knots from his Coastguard days. It is important to note, no one was injured during the process and no pictures were taken for reasons of plausible deniability.

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