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Wood Shake Roofs in Washington, CARE, REPLACEMENT and SERVICE

The natural aging of cedar is one of the many qualities homeowners love about a cedar roof. But that aging can also be problematic if it occurs prematurely. That’s why it’s so important to have basic cedar roof maintenance and cedar wood preservation done on a regular basis. It ensures you’ll enjoy a trouble-free cedar wood roof for 50 years or more. In fact, cedar wood is one of the few roofing materials where its life can be prolonged by basic maintenance and preservation measures.


Two environmental factors begin the natural aging process for cedar wood: sunlight and wet weather. The sun’s ultraviolet rays break down the top cellular layer of the wood and these cells are washed away when it rains. This cycle continues until the entire cedar roof has aged to a silvery gray color. Although this aging is typical of cedar roofs over many years, premature aging is a sign of deterioration of the wood.

Rain slowly removes the natural preservatives from cedar. This allows water to enter the wood, causing the shingles or shakes to expand and contract. When a cedar roof expands and contracts, it’s an open invitation for fungal growth, including moss and algae, in the cracks of the wood. Fungi feed on the wood and begin deteriorating it, leading to premature failure of your cedar roofing system.


Premature aging and premature roof failure can be prevented with yearly basic maintenance. Basic maintenance for a cedar roof includes:

  • Removing all debris, including leaves, tree needles, dirt, etc., from on top of and between the cedar shingles, as well as around chimneys and in roof valleys and corners.

  • Removing algae, moss, or other fungal growth.

  • Trimming back overhanging tree branches that may be touching the roof or shading it and preventing proper drying of your roof.

  • An inspection that examines the condition of the cedar shakes and shingles, their fasteners and other roofing components.

  • Repairing or replacing any damaged cedar shingles or shakes and ridge caps.


Although cedar wood contains a significant amount of natural preservatives, they wear off over time, so as your cedar roof ages, it needs some help in the preservation department. Even if a preservative has been added to the wood prior to installing on your roof, it may need to be supplemented with another coat after five or 10 years, depending on your climate.

Preserving your cedar roof will protect it from curling, cupping, splitting, decaying, fungal growth and other damages caused by sunlight, rain and moisture. Cedar preservation also will extend the life of your roof, saving on reroofing costs.

Cedar roof preservation is most beneficial and lasts longest when natural preservatives in the wood are still present. Having a cedar wood preservative applied 3 to 12 months after roof installation, followed by additional treatments every 8 to 10 years, is a good timeline to follow. However, a first-time preservative treatment can still be applied to your cedar roof even if it has already aged for many years.

Why a new roof Needs an Inspection

So your ready for a new roof and what you don't know about that contractors bid is the ventilation system is about to change! Why is your contactor changing your existing ventilation system when the old one works fine? Because it will look better? Sadly looks are not everything and the majority of the roof installers couldn't even tell you your homes square footage let alone the cubic feet of air intake currentry active with your building design. Ridge vent must have at least an equal amount of soffit ventilation to balance the airflow. There can be more soffit ventilation, but NEVER less soffit ventilation then ridge ventilation. PNWIG has never seen any roof in over 25yrs of inspecting make changes to the air intake when replacing roof cover. So what does this mean for you? ATTIC VENTILATION ISSUES and MOLD!! So your contractor that has bid to change your ventilation needs to know your attics total SF. the square footage of house under roof X .48 divide this number by 20 (for V-600® products), or by 13.5 (for V-300® or Fold-A-Vent products) this will give the lineal feet of product needed to meet a 1/150 vent ratio. If you are only going for a 1/300 (code minimum) vent ratio divide the above result by two. REMEMBER there MUST be an equal amount of soffit vent (in NFVA) to balance the ridge vent. Also a concern is replacing a shake roof that itself breaths differs than the new composition roof about to be installed. Now your contractor is not only about to change your ventilation but also in most cases add roof sheathing and new roof cover that doesn't let the attic breathe as easy.

Box Vents

  • Box vents, also known as hat vents, are not mechanical vents and work better when used with soffit ventilation. They're designed to work with open attics and do not need to be placed close to roof ridges to work optimally. They are also known as low profile vents because they are static and installed over a hole cut into the roof. They use natural winds and convection to move hot air and moisture out of the attic into the air outside. You will usually need more than one on your roof to remove all of the heat and moisture from your attic, with the exact number depending on the square footage of your attic.

Ridge Vents

Continuous ridge vents are more effective because they are installed at the peak of a roof's ridge, allowing for warm air to escape from the attic. It also works better because it creates a vacuum. It has the ability work with vaulted ceilings, and you only need one of them to get the job done for ventilation, as compared to multiple box vents. It is the more expensive option of the two, but it is still non-mechanical, so you will not need to spend money on electrical issues or failures in the system. These systems are best for shingled roofs.


Roofing manufacturers' warranties require a minimum of one square foot of ventilation for every 150sf of attic space for traditional systems, but only one square foot of ventilation for every 300sf when the ridge vent system is used. That is a good indication of the difference in efficiency. There are many good ridge vents on the market, and the continuous vent, as opposed to the individual roof vent, is the most effective. Continuous ridge vents allow hot air to readily escape from the roof peak. Most manufacturers now use a durable plastic, or aluminum, to avoid rust. If using plastic in cold climates, make sure it is rated to withstand subfreezing temperatures.

Roofing Ventilation Tips

Improper ventilation results in warm, moist air generated in the house meeting with colder air in the attic, which causes condensation. Ventilation problems can be seen in a variety of ways, such as blistering and peeling paint on the gable end exteriors because of excessive heat and moisture. Buckling roof shingles are another sign of poor ventilation, as are ice dams in the Midwest and Northeast. Water stains on a ceiling may actually be a result of condensation moisture dripping from under the roof rather than a leak.

Ideally, air circulates under the roof by being drawn up through a continuous soffit vent, through the attic space, and then out the ridge through a continuous ridge vent. This is the smoothest and most efficient system. But few houses have continuous soffit and ridge vents. Most houses, however, do have some type of vent in the roof or an opening at gable ends. Houses with no rafter overhang, or a very short one, may not have soffits. Older houses may not have vents between the rafters leading into the attic space. Venting was not a major problem in older houses because they leaked air everywhere. But with the advent of better roofs and tighter house construction, moisture became a more significant issue.


Calculating the number and size of roof vents is not an exact science, but instead is influenced by the climate, the roof pitch, available locations for vents, and the house's orientation to prevailing winds. The Asphalt Roofing Manufacturers Association states:

"In most cases, a minimum free-flow ventilation area equal to one square foot per 150sf of attic floor area must be designed and properly installed to provide proper ventilation. Where a properly designed and installed eave and ridge ventilation system is employed, a free-flow ventilation area equal to at least one square foot per 300sf of attic floor area is often sufficient. Combination eave and ridge venting is generally recognized as a superior venting technique."

Vent screens should be cleaned regularly because accumulated dust and grime can significantly restrict air movement. Fans connected to thermostats can be placed at gable end openings to draw hot air out of the attic space when temperatures reach a preset level.


Roof Sheathing Field Nail Requirements


5 Steps to Proper Roof Sheathing Installation

APA - The Engineered Wood Association introduces the seventh article in its Builder Tips series of publications.

November 17, 2014

Plywood and OSB are ideal materials for roof sheathing systems ranging from simple single-family residences to large commercial buildings. Follow these simple construction steps for roof sheathing to ensure optimal performance and minimize callbacks.

Step 1: Always Check for a Level Nailing Surface

This can be done with a straight piece of lumber (6 feet to 10 feet long) or a long carpenter’s level. Trusses or rafters should be shimmed as necessary to provide a level nailing surface. If the top chords of trusses or rafters are warped or bowed, install blocking to straighten.

Step 2: Provide Roof Ventilation According to Building Codes

Ventilations hints:

  • A minimum net free ventilation area of 960 square inches for each 1,000 square feet (1/150th) of the ceiling area is required. Net free ventilation area may be reduced to a minimum of 480 square inches for each 1,000 square feet (1/300th) when certain building code provisions are met (see Section R806.2 of the 2012 International Residential Code or Section 1203.2 of the 2012 International Building Code for more details). Note that these are minimum code requirements, which have been found to be adequate under most normal circumstances.
  • Vent exhaust air from kitchens, baths, and laundry to the outdoors with vent pipes that run through the roof cavity or attic to roof ventilators. Do not vent exhaust air directly into roof cavity or attic.
  • Install baffles providing a minimum of 1 inch of clear space between framing and/or under roof sheathing at eaves to ensure that ceiling or roof insulation does not block ventilation paths. For vaulted or cathedral roof construction, provide a free ventilation path from eaves to ridge between all rafters.

Step 3: Fasten Panels Properly

Fasten panels with a minimum of 8d Common (0.131-inch by 2-1/2-inch) nails spaced a maximum of 6 inches on center at supported panel ends and edges. At intermediate supports, fasten panels 12 inches on center. In high-wind areas, more fasteners may be required. Fasteners should be 3/8 inch from panel ends and 3/8 inch from panel edges (see hints below).

For pitched roofs, wear skid-resistant shoes.

On panels with a screened surface or skid-resistant coating, install panels with the non-skid surface up.

Fastening hints:

1. Position panel. Use temporary fasteners at corners if needed to square panel on framing.

2. Install fasteners at one panel end.

3. Remove temporary fasteners at corners.

4. Install intermediate fasteners, starting at panel edge. Use a chalk line or straight edge to align fasteners on framing. Fasten panels in rows across the width, continuing this sequence along the length of the panel. This procedure keeps internal stress from accumulating in panels.

5. Stand on the panel over the framing near the fastener location to ensure contact with framing while driving fasteners. Fasteners should be driven flush with the panel surface. Avoid standing between framing, which can induce panel deflection.

6. For improved performance, consider thicker roof sheathing panels, panel edge clips, or panels with tongue-and-groove edges.

7. A 1/8-inch space between adjacent panel end and edge joints is recommended, unless the panel manufacturer indicates otherwise. Check building code requirements for installation of panel edge clips. Edge clip requirements depend on the relationship of the panel Span Rating to the actual distance between roof framing.

Spacing hints:

Use a 10d box (0.128-inch-by-3-inch) nail as a spacer to gauge 1/8-inch edge and end spacing between panels. Spacer-type panel edge clips are available from some manufacturers. If necessary, trim panel ends to center on framing.

Step 4: Cover Sheathing With Shingle Underlayment Felt

Unless otherwise recommended by the sheathing manufacturer, cover the sheathing with shingle underlayment felt to minimize exposure to weather.

Use shingle underlayment felt conforming to ASTM D226 Type I, ASTM D4869 Type I, or ASTM D6757 (self-adhering polymer modified bitumen sheet underlayment should conform to ASTM D1970) or check roofing manufacturer's recommendations if delays are anticipated during construction. Remove wrinkles and flatten the surface of the shingle underlayment before installing asphalt or fiberglass shingles.

Step 5: Install Shingles According to Manufacturer Recommendations

Shingle hints:

  • If using asphalt or fiberglass shingles, postpone shingle installation as long as possible. This will provide time for roof sheathing to adjust to humidity and moisture conditions.
  • For best appearance, use heavier weight shingles, or laminated or textured shingles. This will mask surface imperfections and reduce the risk of shingle ridging.