Jeremy Stacy, “Listen!” associate producer
Jim Kirby interview
April 9, 2009

For a glossary of roofing terms used in this transcript, read the NRCA’s Roof Buying Guide.

Jeremy Stacy: Please give me your name, title, company and location for the record.

James Kirby: My name is James Kirby. I’m the associate executive director of technical communications for the National Roofing Contractors Association (NRCA) and we are in Rosemont, Ill.

JS: What is the most common roofing material used on residential roofs?

JK: When we're talking about consumers, we're usually talking about steep-slope, residential products. For steep-slope products that would be used for residences, the most common thing would be asphalt shingles.

Asphalt shingles have held their own over the years. There's certainly a comfort level from homeowners in that they understand asphalt shingles. They know the look. They know they can be installed by the vast majority of contractors.

The other [product] that is gaining ground is the metal products — metal panels and metal shingle. They're becoming more popular. I can't give you solid technical reasons why, but they are increasing in their market share.

Other products would be slate, concrete tile, clay tile, wood shingles and wood shakes, metal panels, metal shingles. Those are the basic six or so product types that are out there.

Then there are synthetic products that are available more in the category of recycled components, plastic recycled things — some of the stuff that gets into what you can call the green avenue of things.

JS: What’s the difference between steep-slope and low-slope roofing products?

JK: For all steep-slope products, they are individual overlapping components. The idea is that they require a reasonable slope so that we let water drain over the top of them. If you would consider a steep-slope roof — asphalt shingles or slate or whatever kind — if you were to stand on the ground and shoot a water hose directly up the roof, you would get water to go past all of the individual components.

The idea that steep-slope roofs are individual components and you need gravity and overlap to make things work is ultimately the basic guiding principle for all steep-slope roofs. That's a completely different thing than the way we deal with what we call low-slope roofs that are more membranes and more continuous.

The low-slope materials that the NRCA includes in our NRCA Roofing Manual are built-up roof systems, modified pitchman systems, single-ply systems that include PVC, TPO and EPDM types of membranes. Those are the predominant single-ply types. There are also spray polyurethane foam roof systems and low-slope structural metal panel roof systems. Those are the big broad categories of low-slope roof systems.

From the standpoint of residential roofing, I don't know really which ones of those are more predominant than others. I think we get into some regional issues. It's a very low market share in the residential side of things though.

JS: What kind of recycled products are available?

JK: There are a number of products that have come out within the last five or 10 years that are including recycled products — recycled plastics, recycled rubber and things like that — and they're certainly marketed to be more environmentally friendly.

The caution from the National Roofing Contractors Association would be to be leery or be critical of very long-term warranty promises when a system or a product has only been around for three or four years.

Ultraviolet light does a lot of damage to plastics over a certain amount of years, so does excessive amounts of heat. The low slope industry … has recognized how to deal with the increased temperatures on a roof and how to fabricate the materials to make them appropriate for use as a roof system.

I'm not discouraging use of recycled content products or anything that has claimed to be green. As a consumer I would look for a track record. Look for other installations and get other references that are out there and look for a bit of history on the product.

If you want to be the first guy on the block to say you’re using a green product, fantastic. No problem there. Just simply don't buy the roof because somebody says, "I can give you a very, very long-term product and you'll never have to roof your house again."

Do some research into history performance and then make an informed decision based on that.

JS: Tell me about slate roofs.

JK: Slate is a natural product we get out of the ground. It's very hard. It's very durable. And, it's probably one of the products that have been used longest in the roofing industry — in the United States for sure.

It's also one of the heaviest, so having a good solid structure is important for any of the heavy weight products, which would be slate and the tile products.

JS: What’s the average cost for a slate roof?

JK: We can't get into that. As a trade association, it's actually illegal for us to do that. There's something called the Sherman Act that prevents us from talking about pricing in a venue like this.

JS: How long should a slate roof last?

JK: We have difficulty getting into expected life for slate or any products actually. We try to stay away from that as much as possible. What I can say is that definitely clay tiles, good high-end clay tiles and a good high-end slate roof should be a one-time installation on a home unless there are significant problems or maintenance issue or some type of weather event that would go through and do some damage. Most people are going to get a couple of generations out of a clay tile or a slate roof.

JS: Where would I be most likely to see a slate roof?

JK: Slate is more of a product that's going to be used in the Northeast. There are more slate quarries and things. Transporting things that are extremely heavy gets very costly. So there's a little bit more regionalism with slate and concrete and clay tiles.

JS: Tell me about the wood roofing materials.

JK: The terms we use are wood shakes and wood shingles. A lot of them are cedar-based products. Wood shingles are sawn on both sides so they have a smoother look versus wood shakes. Wood shakes are saw-cut on the bottom side. On the topside, they're usually split.

If you think about splitting a log with an ax and you get a rough surface, that's essentially what the top of a wood shake would look like.

They have different aesthetic appeals because of the top surfaces. Again, they're all multiple layers. Wood shingles have underlayment over a wood deck, where wood shakes have interlayment between the products because of their unevenness.  So there are a couple subtle differences between wood shakes and wood shingles.

JS: What’s the difference between underlayment and interlayment?

JK: An underlayment would be if you envision a wood roof deck — whether that's plywood or OSB (oriented strand board) — before any roofing material is installed — an underlayment would be installed in its entirety from the eve to the ridge. Then your wood shingles would be installed on top of that.

[For] wood shakes, you would put down a layer of wood shake and then you would use a smaller piece of the same material we use for underlayment — a felt underlayment. But, it actually gets put on in a coursing with every single horizontal course of the wood shake. That's because the edges aren’t necessarily going to be as tight. The surface is going to be a little bit more undulating because they are slit on the top versus hand sawn.

It's the traditional way of keeping water out on a shake roof. Interlayment is the way to go with a shake roof, where underlayment would be the wood shingle installation method.

JS: What’s the life of a roof with wood shakes or wood shingles?

JK: They're probably going to be somewhere in between asphalt shingles and slate.

JS: Are wood shakes and shingles regionalized?

JK: You can find those across the country. I would say that's a little bit more of a stylistic roof that's more in the Northwest if we were going to pick just one geographic location, but you can certainly have wood shakes and wood shingles anywhere.

JS: Tell me about tile roofs.

JK:  [There are] two basic types of materials for tile roofs. Clay is one basic component and concrete is another basic component. Concrete tiles are a little bit more susceptible to freeze-thaw damage than clay tiles are. It's just an inherent characteristic of the product.

Just as you see concrete sidewalks absorb moisture when it rains, concrete roof tiles will absorb some moisture. Of course, roofing manufacturers understand that and [concrete tiles] are certainly coated with topical coatings to reduce the amount of water absorption. But, it is one thing to be aware of.

Depending on what geographic location you're in, you may want to do a bit of an assessment with roofing contractors in the area and some of the local building supply locations to see if there are any concrete tiles installed in the area. If there aren’t, I would recommend not going with that product.

Clay tiles are installed across the United States. They're a little bit more durable to the freeze-thaw cycles. Those too are generally glazed products and just inherently they have less absorption of moisture.

Most of these products are more — certainly the S-shaped tile — what we think of as mission-style or Spanish-style. They tend to be more geographic in nature and you're going to see a lot more of that in the Southwest.

That's because there's also a lot of clay in those areas and they're within the materials of the landscape, so they're going to be used more in those areas.

JS: Tell me about asphalt shingles.

JK: Asphalt shingles are individual components that are overlapped. They're installed over underlayment on plywood or OSB deck typically. They're all installed with nails.

NRCA and most of the roofing manufacturers do not recommend staples anymore. We used to use those, but we've realized that's just not an appropriate way to install. Nails are a much better method.

JS: Why?

JK: They don’t have the resistance for pull out as much as nails actually do. And because they're really long and skinny, shingles potentially would pull over top of them if there were any pull out concern whatsoever. The round head of a nail keeps the shingle in place just a little bit better.

Asphalt shingles [come in] basically two different types — three-tab strip shingles or architectural laminated type shingles. Both types come in multiple different weights [and] multiple different color patterns, so there's a lot of aesthetics involved behind asphalt shingles.

A lot of residences are looking to have their asphalt shingle roof go aesthetically with their house, so there's a lot of purchasing based on color and pattern when you're looking at asphalt shingles.

A three-tabbed shingle is a single layer of material. There are two cut outs in it, so a 3- foot-wide, three-tab shingle would appear to be three individual pieces when it's put up on the roof.

An architectural shingle, what we call it is a laminated shingle. There's a little bit more variation in design and the term laminated is used because they laminate at least two pieces if not three pieces on top of each other. With that, you get different types of designs. You get more shadows and depth so the roofs can have a little bit more dimension to them. If you wander around neighborhoods, you can certainly see the difference.

NRCA recommends that all asphalt shingles meet the building code requirements for material standards and the vast majority of all asphalt shingles that can be purchased do meet all of those requires. Most times, buying an asphalt shingle from anyone will at least mean that you meet the material requirements of the building codes in your area.

JS: Tell me about metal shingles.

JK: Metal shingles are exactly what they sound like. They're small individual components that either overlap or have actual interlocking seams on the edges to connect them all together and hold them into place and keep them water shedding.

Metal shingles have those kind of components to them and usually either individual clips hold them in place with a couple of nails fastened into the roof deck.

Or, you can have long panels that run from the eave to the ridge. Those will typically be flat in the pan section and then have vertical seems, which get overlapped and locked together or have a snap on the seam to keep them water shedding.

JS: What types of metal are used on roofs?

JK: Multiple types of metal can work. The vast majority that would be installed on homes would either be aluminum or steel that is pre-painted from the manufacturer, so there's a good variety of color choices. You could also get into copper shingles [and] copper panels. There's some zinc materials that are available. That has a more of a grayish appearance to it. So there are a lot of aesthetic variations and patterns that you can come up with as well with metal shingles.

They again are installed over a solid deck — plywood or OSB — with an underlayment underneath them before the metal shingles or the metal shingle panels are installed. 

JS: Is there any type of regionalization with metal roofs?

JK: They seem to cross all geographic locations pretty well.

JS: What can you tell me about authorized roofing installers?

JK: There are manufacturers that will approve contractors — call them authorized applicators. So certain contractors become very familiar with certain product types and then they can be authorized contractors of a certain product line of a manufacturer. There's no requirement to be an authorized installer.

Generally this gives a little bit of a marketing benefit to the roofing contractor because … the homeowner [has] a comfort level that this particular contractor is very familiar with a product line. That works very well.

And roofing contractors become very familiar on their own regardless of authorized installer labeling or certification. They just become more familiar with certain product lines and are more willing to install those than things they aren't as familiar with.

As a homeowner, I would not ask a roofing contractor to do something that they are not comfortable with. Having general discussions with your roofing contractor and finding out what they commonly [install] and what they understand is really a good way to ease your own mind.

If that contractor doesn't feel comfortable or doesn't have the experience installing what you want to have installed, that's probably a good reason to go out and find a different roofing contractor. Just like in other areas of the house, if a contractor is used to installing kitchens, you may not want them installing your bathroom.

JS: What kind of questions should homeowners ask roofing contractors?

JK: Homeowners should never be intimidated in asking any and all kind of questions. What materials are you going to use? Who's going to be on my roof? Do you have the proper insurance? Can I get recommendations or references of other installations you've done? As a homeowner, I would recommend checking the Better Business Bureau for multiple complaints.

Getting a thorough and complete project bid from a roofing contractor is a very good idea. The more explanation that's on the bid without being verbose is a good idea. Understanding what the limitations of warranties are as well.

Ask for sample warranties of both the material and [workmanship]. Depending on who the contractor is, some will give a one- or two-year warranty on workmanship. A lot of the authorized installers are required by the manufacturers to do those, whereas some of the other contractors may or may not do that. It's just something to discuss and understand. The more you pay, the more comfort level you should probably have.

When homeowners call up and say "I've got three bids. How do I analyze these?"  I tell them to at least attempt to get more detail out of the lesser-detailed proposal and don't necessarily base it on the lowest dollar value.

You may be getting the lowest immediate cost, but if one proposal specifies a 25-year shingle and one proposal specifies a 35-year shingle, then you may end up with a longer life for a little bit more money and your dollars per year may actually end up being lower even though you pay a little bit more up front.

There's a number of ways to think about how to select the proper roofing contractor and roofing material and what the overall cost of the project is.

On the NRCA website we have a consumer segment of that website and we have a bunch of information consumers can read and download — guidelines for selecting a contractor. There's actually a contractor qualification form. We have a checkup guide for homeowners on existing roofs. And the one that really hits home on the conversation we've had today is a brochure we have called FYI Buying a New Roof and Getting Your Money's Worth.

Most roofing contractors that I have contact with prefer to work with an informed homeowner. The words mean more to the homeowner when you're having a discussion. As a quick example, if a home owner already knows what ice dam protection means and they want it, then [they] aren't surprised when a contractor says, "You live in Chicago. You need ice dame protection." If the homeowner already know that's going to be a part of their roof, then there's no discussion as to why it's necessary and what's it's all about. It makes things easier.