The Balloon Frame. The balloon frame (Fig. 21) is built by spiking or nailing all timbers together, and is the cheapest form of construction for a frame house. The studs are usually continuous from the sill to the plate, on the sides of the house, except at the openings, and in the gables to the rafters, if pieces of the right length can be secured, otherwise they are usually pieced by means of a fished joint.

The ribband, or ledger board (a), is cut into them to support the floor joists of the second floor.

The braces usually extend from the second or third stud . on the sill to about 2'6" from the plate on the corner posts. though they are sometimes not extended above the second floor. Braces are frequently made of 1' or 1 1/8" stock, being let into the studding flush with the outside of the wall, as at c. The better method is to use a2" x 4", as shown at d. It is characteristic of this form of construction to use only the lightest timbers, and, unlike the full and half frames, to build one piece at a time.

A balloon frame is a fire trap unless bridged by pieces of scantling (b), which are cut between the studs to prevent the circulation of air, thereby reducing the danger from fire. Bridging also makes it difficult for vermin to pass from one story to another, and adds much to the warmth and stiffness of the house. It is a good plan to fill in between the floor joists upon the sills with a brick nogging (f), which assists the fire and vermin-resisting qualities of the building. In the full and combination frames this protection is formed by the solid girts.

A well-built balloon frame is satisfactory for a moderate-sized house, but since it invites poor work and a certain class of builders cannot resist such a temptation, this form of construction has a worse reputation than it deserves. In many cities a balloon frame is not accepted within the fire limits, though a half frame usually will be accepted wherever a wooden building is allowed.