An asphalt shingle underlayment is typically dry felt, that may be injected or coated with an asphalt saturant, or a synthetic sheet. The use of an underlayment is recommended for the following reasons:
– Resins may exude from the wood board decking. Underlayment protects roof shingles from the resins that may be released.
– Underlayments protect decking material from wind-driven rain that may penetrate the shingle layers.
– To validate their limited warranties, many manufacturers require the use of underlayment.
– The use of underlayments, particularly heavier grades, reduces “picture framing.” According to CASMA, picture framing is the visible outline of deck panels caused by irregularities in roof decking thicknesses.
– To obtain a Class A fire resistance rating, underlayments should be used underneath shingles.
Yes, you can definitely apply new shingles over existing shingles. Although, it depends on the condition of the roof. If the roof has one layer of shingles that are lying flat and the deck is in good condition, the existing shingles typically do not have to be removed. Check with local officials to make sure that your home/ building codes are being followed. During re-roofing is a good opportunity to examine roof ventilation to ensure vents are sufficient in number, positioned properly and are unobstructed.
Proper performance from shingles installed and used in cold weather climates can be achieved by following the recommendations listed below:
– Make sure that the roof is properly ventilated.
– Be careful when using shingles in cold weather. They tend to get brittle and may crack or break. Try not to throw, drop or bend shingles.
– If you are in an area that experiences freezing winter temperatures, eaves protection should be used to reduce water damage from ice dam formation. Use self-adhering eave protector membranes.
– Hand seal asphalt roof shingles in cold weather with an asphaltic cement recommended by the manufacturer.
– When applying ridge caps, keep the shingles that are being used as ridge caps in a warm place so that they will be flexible enough to bend.
– When re-covering an existing roof with new shingles, make sure that the old shingles are flat.
– In areas that receive high amounts of snowfall, try not to damage shingles when removing snow. Damage caused by snow removal is not covered under our limited material warranty.
– Use caution if walking on a roof in the winter time. The sealant bond between shingles can become quite brittle in cold weather. Therefore, traffic on the roof may cause sealant bonds to break.
Pioneer agrees with and supports the ARMA position that nails are the preferred method of fastening asphalt roof shingles due to their superior holding strength. The following fastening tips apply to most of the shingles Pioneer uses; (check specific product application instructions for further information):
– A minimum of four fasteners per shingle are used.
– Correctly place and position fasteners below the sealant strip, but above the cut-out on three tab shingles, and in the nail line on laminated shingles.
– The fasteners must be straight and flush with the surface of the shingle, not sunk into the shingle or sticking up at any point.
– Make sure there is correct penetration of the deck as specified by ARMA and the NRCA.
The plastic release film on the back of roofing shingles does not need to be removed. The sole purpose of this tape is to prevent the shingles from sticking together in the package. Once the shingles have been removed from the package and are applied in the correct orientation on the roof, the release tape serves no purpose whatsoever. The shingle sealant, which bonds the shingles together, is located elsewhere on the shingle and will seal succeeding courses of the shingles together on the roof when warmed by the heat of the sun, soon after application.
Hail can affect asphalt roofing shingles. The damage caused by hail can be classified into two groups: Aesthetic Damage and Functional Damage. Aesthetic Damage results in slight granule loss and the life of the shingle is usually not affected. Functional Damage is characterized by substantial granule loss or cracking or penetration of the shingle. Functional Damage may result in short term leaks or a reduction of the life expectancy of the shingle. According to CASMA Technical Bulletin No. 14, there are several factors that impact how roofing shingles perform in hail:
– Size and density of hailstones – Larger heavy stones will cause more severe damage.
– Age of the shingles – Newer roofing shingles are more resistant than older shingles, as the asphalt is less brittle and better able to absorb the impact energy.
– Angle of hail impact – Hail which strikes the roof at a 90° angle is more likely to cause shingle fractures, while hail that strikes the roof obliquely is more likely to result in spots of granule loss.
– Temperature – Colder temperature will be more likely to cause fractures as the asphalt will be more brittle than in warmer weather.
– Roof deck conditions – Solid roof decks on moderately spaced trusses offer better support to the shingle surface in resisting hail damage. Shingles on flimsy or rotted decking can be more easily fractured.
Buckling is when ridges form along the length of the shingle, with the ridge spacing usually coincidental with deck board joints. These ridges are caused by the shingle being distorted from the movement of the deck. Buckling can occur with any deck type, but is more common with board decks, and less common on plywood/OSB decks. Buckling can occur when a new roof is installed, even if the old roof did not show any buckles; when the roof is stripped, the deck may be exposed to moisture, causing dimensional changes in the supporting lumber.
The following will help to prevent buckling:
– Apply shingles as specified by the roofing material manufacturer.
– Make sure you have sufficient attic ventilation.
– Decking material should not be exposed to water before or after application.
– Use manufacturer approved wood decking materials and make sure that they are conditioned to be at moisture equilibrium with the job site environment.
– Cover older dimensional lumber decks with a thin plywood sheathing prior to shingle installation.