Because the deck performance can have a strong effect on shingle performance, most shingle manufacturers require certain minimum decking standards. The deck must be structurally stable, solid, smooth and secured adequately to rafters or trusses.
Basically there are two types of shingle underlayment: water-resistant and waterproof. Shingle manufacturers recommend the use of underlayment except on roof-over installations.
Water-resistant shingle underlayment - Resistant is the key word. It is often referred to as roofing felt, tarpaper or asphalt felt. Sun and moisture degrade the material quickly, and then the nails penetrate the material. If the wind blows off a few shingles, it serves as a backup – making the difference between a few drips and a waterfall.
Waterproof shingle underlayment - Waterproof underlayments were designed to seal the roof and to prevent water from getting inside the building due to ice dams and/or wind driven rain. Unlike the standard felt underlayment, it is unaffected by moisture so it does not wrinkle.
Drip edge flashing
Though not used throughout the United States, drip edge flashing is often installed to prevent wind driven rain from getting under the underlayment and damaging the sheathing along the edges.
Common findings found during an inspection:
workmanship. But if everything else is correct, a roof with misaligned shingles will
probably shed water.
The bottom tabs are always cut off. By cutting off the bottom tabs, the self-sealing adhesive can be placed along the bottom of the overlying first course to help prevent blow off.
The use of a whole shingle makes that impossible, and also creates a slight hump under the bottom of the second course that could play a role in damming.
NOTE: You won’t have much luck trying to convince a roofing contractor with 30 years’ experience that his starter courses have been wrong, but it’s important to note if it does not comply with the manufacturer’s specifications, it could have an influence on the limited warranty, but it doesn’t void the warranty because shingles warranties are for product defects not installation error.
3. Overhangs – Inadequate shingle overhang is an indication of amateur workmanship. Insufficient overhangs typically cause water damage to fascia and rake boards. Excessive overhang is also common.When shingles overhang too much, they are more likely to have wind up lift and to blow off. Also over time, the excessive shingle will curl over to create an unsightly view.
4. Improper Nailing – Most shingle manufacturers prefer nails to staples. Proper nail placement is critical in shingle performance. Incorrect nailing or lack of nails can result in shingle blow off and/or shingles slipping out of place.
Additional common problems:
After the precursory inspection of the new roof, it’s time to check for a few more common problems that can be seen by the observant eye.
5. Check for holes: On steep roofs, roofers will often install a toe board (2x4"nailed through shingles) to hold materials and/or roofers on the roof. After shingles are complete, the board is removed and the nail holes are either forgotten or caulked.
6. Normal and Premature Decline: When inspecting older shingles, it can be difficult to distinguish between what is “normal for the age” decline and “premature” decline.
Research shows shingles rapidly age during the first years after installation, some granule loss, minor curling around edges and even small blisters may develop, all considered normal.
7. Lack of Ventilation – Research has shown improperly vented attics or air space inhibits air movement and usually increases moisture content. Under these conditions, heat builds up and shortens the shingle life.
The big picture – When inspecting a roof, it wise to first look at the big picture. I step back far enough to get a clear view of the house and its roof. As I slowly walk around the house looking up at the roof, I make mental notes of anything unusual, such as unevenness, sags, dips, or obvious damage.
These observations will be worthy of a more focused look later, because dips or irregularities can be prone to leak. Obviously sags or unevenness could be an indication of a structural problem and will be investigated when inspecting the attic.
****Please note this is a condensed article directed at informing about some basics of roofing, not educating about how to install roofs.