This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
With Sill. Joists are also "gained" into the sill, as shown in Fig. 94, in which case a mortise is cut in the sill and a corresponding tenon is cut in the end of the joist. The mortise was illustrated and described in connection with the sill, while the end of the joist is cut as shown in Fig. 94, the tenon being about 4 inches deep and gained into the sill about 2 inches. This brings the bottom of the joist flush with the bottom of the sill, and the top of the joist somewhat above the top of the sill, according to the depth of the joist. The top of a 10-inch joist would come 4 inches above the top of a 6-inch sill, and the joist would rest partly on the masonry wall, thus relieving the connection of a part of the stress due to the weight of the loaded joist. A common but very bad method of framing the joist to the sill is simply to "cut it over" the sill without mortising the latter, as shown in Fig. 147. This does not make a strong connection even when the joist rests partly on the masonry wall; and if it is not so supported it is almost sure to fail by splitting, as shown in Fig. 148, under a very small loading. In fact, it would be much stronger if the joists were turned upside down. Frequently the joist is cut as shown in Fig. 149, where the tenon is sunk into a mortise cut in the sill, thus bringing the top of the joists flush with the top of the sill; but in this case the bottom of the joists will almost invari-bly drop below the bottom of the sill and the wall must be cut away to make room for it, as shown in Fig. 140. It is also weak in the same way as is the connection shown in Fig. 148.
Fig. 147. Bad Method of Framing Joist to Sill.