Fireplaces come in two basic types-masonry and pre-fabricated. Masonry fireplaces are built of bricks or stone and mortar. They are constructed on-site and form part of the structure of your home. Pre-fabricated fireplaces are built in factories and have metal chimneys and lightweight metal fireboxes. A common hybrid of the two types uses a heavier metal firebox and attaches it to a brick and mortar chimney.
Masonry fireplaces generally use yellowish firebrick for the firebox and ordinary red brick for the above-roof portion of the chimney. Just above the damper it will crook slightly backwards in order to provide a smoke shelf for those times when the smoke gets a little too heavy and cool and wants to come back down.
When you read the word "fireplace," a masonry fireplace is probably the first image that pops into your head. They are pleasant to look at and fairly easy to care for. With a little maintenance, these fireplaces are likely to last as long as the rest of your home.
Masonry fireplaces can weigh as much as 6 or even 7 tons. This means they need an extensive footing to support them. Absent such footing, these fireplaces can shift and crack, sometimes with disastrous results. The flames that were supposed to go up the chimney can escape into your home instead. Even with a properly set masonry fireplace you should check periodically for signs of movement and settling. The seam near the front, where the outside hearth material meets the firebrick is one place where such settling can be noticeable.
Similarly, you should inspect the chimney for wear and tear. As a preventive measure, apply waterproofing to protect the chimney from rain and snow.
Prefabricated fireplaces have been around since 1980 or so. A prefab generally has a firebox composed of cast refractory panels. Looking up past the damper will reveal a round metal chimney that ascends through the roof. Outside, the chimney may be left as is encased in an artificial brick housing. (Real brick would be too heavy for the roof to support.)
The fireplace and chimney are manufacture separately but engineered to work together. It is imperative that you use the chimney specified for the fireplace you purchase. This isn't a case where any old chimney will do.
Prefab fireplaces may be a little fussier to install. The manufacturer will have specifications regarding the amount of air space required between the chimney and any wood framing. Wood too close to the chimney can dry out and eventually catch fire without being touched by a single spark.
Prefabs are also less sturdy. Even a small chimney fire can damage these units, so regular cleaning is even more essential. And even with the best maintenance, they do wear out.