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New BC Building Code Rain Screen Requirement

Journal Of Commerce

The new 2006 BC Building Code has been released and among the changes, is a new requirement for a capillary break (rain screen).


The new 2006 BC Building Code has been released and among the changes, is a new requirement for a capillary break (rain screen).

Any building permits issued after December 15, 2006 by most B.C. municipalities west of Hope and on Vancouver Island will require the installation of a 10mm capillary break between the cladding and building paper or wrap.

A capillary break basically encompasses the use of wood furring strips or a positive drainage material. Products are available primarily for use on wood or fibre cement siding while others are specifically for stucco, stone, and other masonry applications. But what does a capillary break do?

A capillary break allows moisture to drain behind the cladding, lets air dry any excess moisture, and restrains the ability of water droplets to ”bridge” from the back of the cladding to the building wrap or through any penetrations in the system.

This means the walls in our buildings will be drier and much less susceptible to water penetration and moisture-related problems.

While some in the construction industry have resisted the capillary break (rain screen) requirement, it is now a new code requirement! After all the cost, time, lawsuits and other issues related to ‘leaky condo’ problems on the West Coast (and elsewhere for that matter), this new requirement is ‘insurance’ to home and building owners for years to come! It is a truly a win-win situation!

As part of the new code, products used to create a capillary break/rain screen must not fill more than 20% of the capillary/rain screen space. The use of furring strips, typically installed on 8” to 16” centres, can create some problems here.

This is especially true on structures with numerous corners, windows and doors.

Also, there is still some debate about the total effectiveness of furring strips when water finds its way between the strapping and the building wrap. Some tests indicate that there is much more ‘water hang-up’ in the systems using furring strips than with the use of products giving more positive drainage.

Bernie Jess of Catalina Enterprises, who has long been involved with moisture issues in buildings, said “Those of us who were involved in addressing the ‘leaky condo’ problems of the ’90’s, realized that furring strips were perhaps not the total answer. At the time it was the best solution available to us. Now, however, there are products available that are more of that total answer.”

While product-only costs for wood strips may be less, owners and contractors really need to look at the installed cost savings of using a drainage material, with less labour and time-on-the-job costs. Wood furring strips may also require the use of expensive fasteners when some pressure-treated materials are used, due to their corrosive effects. Others may debate the fire-safety of wood furring strips but some products available have a Class A Fire Rating!

But whatever rain screen material is used, in the long-run everyone benefits from drier homes!


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