When most think about roofing, the first thing that comes to mind is probably shingles--and maybe a little apprehension about heights. But in reality, shingles (and climbing up ladders) are only pieces of a very important puzzle that keeps your roof from leaking and letting in all sorts of unwanted environmental extras.
Roofing felt, also known sometimes as tar or building paper, is often used as an underlayment beneath your roof's shingles and above the roof's actual decking (usual particle board or plywood). It is placed down before you install your shingles, tiling or other final layer material.
Well, technically, what you'll see at your Atlanta Home Depot or Lowe's these days is going to be polyester or fiberglass. These newer materials, especially fiberglass, are much more durable than the felt used in the past. The paper usually comes in fairly large rolls, about 36" wide; it's pre-marked at set intervals, so you'll know where to cut in order to get even coverage.
Why the need for added protection?
There are many reasons, not the least of which being that if it happens to rain before you complete a job (and it will!) the roofing felt will act as a water-repellant barrier. The paper is usually soaked in asphalt (hence the tar nickname) to add to its hydrophobic quality. After completion, the felt will continue to give your home added protection from the elements.
How you lay the paper is very important. If you have an angled roof, start at the bottom, near the gutter, and work your way back to the apex. This way, should water somehow get beneath your shingles (or if one gets damaged), it'll flow right down to your gutter system. Also, don't be fooled by the relative ease of installing the paper; bumps or wrinkles that come up will greatly reduce the effectiveness of the material.
If you're wondering about brands, Owens Corning is a good one; they've been around a long time and are trusted by experts and beginners alike. However, if you're not feeling up to the challenge of felt installation, there are a number of Alanta-area contractors that would be happy to step in and take care of it for you!