Everyone has seen a bad remodel.

You've seen the house where the new addition looks like a big shed bumped up against the house, or the second story that looks as if it could have fallen from space and just happened to land on that particular house.

The key to achieving a seamless blend of the old and the new has to do with the roof. The shape (or massing) of the roof is critical. It often takes the trained eye of an architect to help you with this design issue to ensure that your renovated home’s construction looks well-integrated and successfully executed. Once the massing issues are resolved and the style of the home established, the material used on the roof will be the next decision key to the success of the project.

One of our clients hired us to remodel an old addition to help it blend in with the rest of the house. They knew they would have to redo the roof for two reasons: First, the old addition's roof was flat, and second, it was leaking. Flat roofs that are not well-maintained tend to have that problem at some point.

These clients understood that a roof has a lot to do with defining a house's personality. They felt that the 1920s prairie style of their home called for the look of a classic tiled roof, so they expanded their project from just adding a new roof to the addition to changing the roofing materials on the existing house as well. However, the existing roof structure couldn't handle the weight of the tiles. Concrete and clay tiles tip the scales at 500 to 800 pounds per square foot (or 100 square feet or a 10-foot by 10-foot area of the roof) for the lightweight versions, and 900 to 1,200 pounds per square foot for regular tiles.

Reinforcing the structure of the roof added a few more months to their construction schedule and more than a few dollars to their budget, but being able to upgrade to the tile roof with the impact it made on the curb appeal made it worth the investment to them.

The selection of the roofing material is an important aspect of a remodel when you are adding on to a home. While some projects can get away with matching the material of the addition to the existing roofing material, this may be a good time to replace all the shingles. This is one surefire way to make the addition more seamless. It will look great and the entire roof can age and wear at the same rate.

When deciding on a roofing material, there is a lot to consider. Cost, as well as aesthetics, are factors.

Asphalt shingle roofs usually cost from $50-$150 per square foot. Though building codes generally allow up to three layers of shingles, tearing off the existing shingles is highly recommended to get a roof that lays flat and looks sharp. This will add another $30-$50 per square foot to the cost.

Metal roofing and concrete tiles may start at $100 per square foot and run up to $600 or more for coated steel and copper. Ceramic tile and slate are also considerably more than asphalt shingles. Clay tiles can cost $300-$500 per square foot. Slate, with its need for skilled and experienced craftsmen, can cost up to $1,000 a square foot.

Initial cost is just one consideration, however. You'll be lucky to get 20 years from a cheap asphalt shingle, but a good slate roof could easily last a hundred years or more. Some cement and metal roofing products come with 50-year warranties, so spending more up front can buy more years of maintenance-free service from your roof.

For commercial projects, architects sometimes use a "life-cycle cost" comparison that factors in maintenance and replacement costs to justify spending today's dollars on a material with lasting value. By that calculation, cement tile or even slate could be a good buy in the long run.

Fire safety, pitch/snow buildup and energy efficiency are among other considerations when selecting a roofing material. Light-colored roofing material will help keep your home cooler in the summer. Smooth materials will shed snow, while materials with rougher surfaces will retain it and let it act as an insulation factor during the cold months. Take a good look at code requirements in your area, how much hot sun your roof is likely to encounter and the precipitation it will need to shed. These questions will help pinpoint your ideal material.

And that roof material can make or break your home remodel. Just ask our friend’s with the tile roof. Even after all the added expense and time (including surviving a few more rain storms with their roof torn apart!), our clients are happy with their new tile roof. Not only do they have the curb appeal they desired, their addition looks completely at home.

Ann Robinson and Annie V. Schwemmer are the Principal Architects and co-founders of a residential architectural firm focused on life-changing remodeling designs at RenovationDesignGroup.com. Send comments or questions to [email protected]