Q–My house was built using steeply-pitched roof trusses. There is a huge amount of wasted space up in the attic. I intend to add a room up there. Can I easily modify the trusses to create this space or must I tear off the roof and start over? Is there a truss configuration that will allow you to create a room or storage space economically?
A–Twelve years ago, I made the same stupid mistake your builder did by using common roof trusses on a steeply-pitched roof. After the roof was on and just before the drywall was installed, the homeowner brought to my attention the vast amount of useless space in the attic.
The next day I noticed a big truss poster on the wall of the lumber company. Much to my surprise, there was a special truss with a large box shape inside the center of the truss. I immediately saw that if you used 10 or 15 of these trusses side by side, you could instantly create a giant room.
One of my favorite building tasks is roof framing. There is nothing quite like cutting rafters and watching them fit like a glove. However, the process is very labor intensive. Furthermore, the span of rafters in a common framed system is limited by the size and species of the lumber.
Just over 400 years ago, an Italian architect named Andea Palladio developed the concept of using rigid triangles in trusses. Trusses are a building marvel because they allow lightweight, interconnected framing members to safely carry loads previously reserved for large-sized beams.
Maintaining the connection points and the overall design in your trusses is critical to the structural integrity. When a truss is loaded, each piece of lumber is carrying a load. If you cut or modify any member of a truss without expert engineering supervision, you can cause significant structural damage to the truss and the overall roof structure. Trusses can be modified, but it can be very expensive and time-consuming. A residential structural engineer or a local truss fabrication shop will be able to advise you of your options.
If you decide to start over, which may be the cheapest option, the attic truss can magically create the room you are looking for. Depending upon the span of the truss and the slope of the roof, the room within the truss can be enormous. For example, if your truss span is 34 feet and the roof slope is a 12/12 pitch (it rises 12 inches for every foot it moves toward the center of the truss), the room inside the truss will be 16 feet wide with a full ceiling height of 8 feet. Think how big that space would be if your house is 50 or 60 feet long.
If you just desire storage space in an trussed attic, that is also possible. These trusses are often called light storage trusses. Often a rectangular-size space is created inside the overall large triangle of the truss. The height of the interior box within the storage truss is usually never over 5 feet high. This prohibits homeowners from attempting to transform the space into a full fledged room, but these trusses are ideal for people who want a storage place for boxes, camping gear, seasonal decorations, etc. Light storage trusses are perfect for houses that have no basements.
The cost of these space-creating trusses is very modest. A regular common truss with a 24-foot span and a 10/12 roof pitch with no storage space costs $69 in my area. This same truss, framed as a light storage truss, costs just $87. If you want a full-blown-attic truss with a room, the cost of a single truss is just $158.
Had you incorporated a full-sized-attic truss in your roof, I’ll bet you could have created a 15-by-30-foot room for less than $1,350. This slight charge is nothing compared to what it probably will cost you to make the modifications. Keep in mind that once the attic truss is in place, no additional rough lumber is required to finish the space. All that is needed is the plywood subfloor.
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Have questions about the remodeling process? Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, Ohio 45236-0352. Questions will be answered only in the column.
For a list of 10 room sizes inside different length and pitch attic trusses, simple truss-erection guidelines, and other tips on cutting common roof rafters, send $2 and your name and address to Tim Carter at the above address. Ask for Builder Bulletin No. 198.
For a list of past Builder Bulletins and a wide variety of individual job bid sheets, send a business-size, stamped, self-addressed envelope to the same address.
Ask the Contractor can also be accessed via the Internet at http://www.chicago.tribune.com/homes/articles/askcon.
