Topics
QUESTION
• Do you realize that when it is time to replace a Roof, it is more involved than buying shingles?
• Do you realize that when it is time to replace a Roof, it is more involved than buying shingles?
WHAT IS A ROOF SYSTEM?
• A Roof System is made up of all of the components
required to make a weathertight seal between exterior elements
- rain, snow and wind - and the interior of the structure.
Although related, the roof does not protect the interior space
of the house from attic moisture, caused by inferior air-sealing,
insulation and ventilation. In residential sloped roofing,
the building envelope, very seldom, includes the roof itself
- it is an umbrella to shed water.
COMPONENTS OF A ROOF SYSTEM
- WOOD ROOF DECK:
> if your house was built prior to 1957, it probably has a board or plank deck. As long as the attic is dry and well ventilated, board decks are very strong. If subjected to a lot of condensation or other moisture, the boards can be warped and deteriorated, making it advisable to sheath over with plywood. Since 1957, most roofs had plywood installed. The plywood should be 1/2", however, many are decked with 3/8" or 7/16". A lot of houses built in the late 70's and the 80's had 7/16" aspenite decks. These prove to be very poor if there are condensation problems in the attic
> all roof decks should be inspected, prior to or during the roof replacement project. If this is not done in the attic space prior to roofing then it has to be inspected carefully, during the project. Rotted wood must be replaced, before the new materials are installed. - EAVE PROTECTION: [two items make up this component]
* Drip Edge or Metal Starter Strip
> deflects water into the Gutters.
> supports the bottom row of asphalt shingles.
> discourages rodents from gaining access to the attic space.
*Eave Underlay
> this is required by the Building Code, to a minimum line 12" inside any exterior wall [of a heated space]. This usually means 2x3', or 6' wide of rolled material is required. [3' is okay if the soffit is less than 12" wide and the roof pitch is equal-to or less-than 5/12'].
> contractors should offer a choice of a Fibreglass Base Sheet [as standard] or Ice & Water Membrane [as deluxe upgrade]. If you have problems with ice damming, you should go with the upgrade. - UNDERLAY: [to the balance of the Roof Deck]
> if the roof pitch is equal-to or less-than 6/12', it is good roofing practice to cover the entire roof deck with Underlay. It is the Underlay that provides full [exterior] water protection - shingles on their own will not prevent hard, wind-driven rain from being forced under the shingles and then through the wood deck. Shingles rely on gravity to shed water.
> if you use the right underlay with a fibreglass base-mat shingle, such as the Certainteed products, you will have a Class-A Fire Rated Roof System. This could result in a discount on your home insurance premium. - VENTILATION: [for the Attic Space]
> proper Ventilation of the attic space is critical, not only for summer comfort in the home, but even more so, for condensation control in the winter months.
> there is a formula to calculate the total amount of ventilation required for any attic over heated space. This is a minimum standard of the Building Code. Ideally, the total amount should be divided equally, between Roof & Soffit/Eaves. [If this cannot be achieved, the Roof Vent area may be doubled.]
> the number of Vents required is based on the total square inches needed, and then divided by the size of Vents the contractor is using. Don't let a contractor say they will add "#" roof vents, unless they also state the size and how they figured it out. Otherwise, you may VOID the manufacturer's warranty. Also, make sure any contractor considers the soffit venting, not just the roof venting.
> If possible, ridge venting for the roof is advisable, as it provides the most consistent airflow. There are several types of Roof Vents available today; we can assist in choosing the most effective type for your needs. Also, roof venting needs to be as close to the ridge as possible - not 2'+ below the ridge.
> WARNING: If ventilation is upgraded, but there are low standards of air-sealing and insulation, causing "air filtration" into the attic, energy costs may increase and interior moisture damage may occur. - VENTILATION [Exhausting of Mechanical Fans]:
> when there are exhaust fans in washrooms, laundry rooms and over kitchen stoves, it is imperative to make certain they are exhausted to the outside and not just into the attic space.
> There are Damper Vents available in the proper sizes for these exhaust fans. Don't use static roof vents, as they won't always duct the warm, moist air to the exterior of the attic. - FLASHING:
* All metal Flashing should be fabricated, using pre-painted Steel. This is a maintenance-free material, does not rust and has less than 1/2 the expansion and contraction, of Aluminium.
* Valleys > with asphalt shingles, there are 2 accepted methods in our climate
(1) Open with 36" wide Underlay on top of wood, plus 24" wide pre-painted Steel. The shingles then are installed over the steel, to within 4-6" of the centreline.
(2) Closed with 36" wide Ice & Watershield on top of wood, and then the shingles go through the valley to a point at least 18" past the centreline, in the one direction. The shingles, from the other direction are cut-off in a straight line, 2" short of the centreline
NOTE: Never accept "rolled roofing" material in valleys [for our climate].
* Brick Chimneys and Skylights
> should have Ice & Watershield applied at the perimeter and then have pre-painted Steel, "counter", "skirt" and "back-pan" Flashing installed.
* Dormers & Abutments [from one roof plane to another]
> should have pre-painted Steel "trim", "wall" or "counter" Flashing installed,
* Plumbing Stacks
> require new "flashing boots". - SHINGLES:
> the preceding components are what give the foundation for the finished, or visible portion of a Roof System.
> Asphalt Shingles are available in many styles and weights, today. You can pick from the standard 3-tab/25 Year, right up to a Designer-laminated/60 Year type.
> Other types of Roof Systems are also available: Metal, Wood, Tile, Slate, etc. Let It Rain Ltd. does many of these systems, if that is your preference of design.
