Beam, in architecture, is the largest piece of timber employed in the erection of edifices : it is laid across walls, and serves to support the principal rafters, which arc framed into it.

The proportions of beams vary according to their length ; and to prevent accidents that might happen from their breaking, through frauds in building houses, they must be fixed, in the metropolis and its vicinity, by statute, in the following manner: - A beam 15 feet in length ought to be 7 inches on one side of its square, and 5 on the other; if it be 16 feet long, one side must be 8 inches, and the other 6; increasing progressively according to its length. In the country, however, beams are in general made comparatively stronger, especially in places where timber can be purchased at a more reasonable price.