a rain screen is an airspace behind the exterior siding. it allows any water the might find its way behind the siding to drain. thus, the building structure is better protected against water infiltration and the siding is more durable. nothing new here – “rain screens” can be found in buildings that are hundreds of years old (it’s a major reason these buildings have lasted so long). however, in our miserly quest to build cheaply (so the wall street /thieves bankers can pocket the dollars!), we’ve lost our way a bit. the introduction of a rain screen into a wall assembly is relatively simple – but, it does add some costs. historically, those costs have not been supported in the post-war building boom. to satisfy the money guys, we only need to build houses that last 25-30 years (typical mortgage period). so, that’s what we have been doing. its time we change that.
the rain screen employed at 363HOUSE is VERY simple. basically, it consists of three components: 1) house wrap as the drainage plane. this protects the exterior surface of the structural wall (SIPs) from water. house wrap also allows any trapped moisture behind to escape via vapor diffusion. 2) air space – we are using 1×3 strapping to create a 3/4″ air space between backside of clapboard siding and face of structural sheathing (SIPs). the air space is of sufficient depth to allow water to drain and provide air flow to promote drying and pressure equalization. 3) flash and vent – the only “tricky” detail with a rain screen is paying close attention to flashing details. basically, the flashing must bridge the air space – so, it spans from the house wrap outbound to the exterior surface of siding. this is necessary for any water that might be draining down the drainage plane (house wrap) to find its way out above wall penetrations (doors, windows, lights, vents, etc.). venting is important to allow any water to drain and air to flow. so, we are using 3/4″ thick corrugated plastic vents with insect screen at the bottom and the top of the 1×3 strapping.
so, when all is detailed AND installed properly, the rain screen will protect our structure and siding from the potential damages of water/moisture. this will result in long-term durability and lower maintenance. all of this for a few thousand dollars, labor and material.
siding and trim installation starts this coming week!