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.
Before the clapboarding or shingles of the walls can be completed, the porch and piazza finish must be put up. The floors should be framed with the joists running parallel with the house walls so that the boards will run in and out, and they must also pitch away from the house at about the rate of two inches in twelve feet. The tops of the piazza joists should be set about six inches below the main house and it is a good plan to bevel off the tops, leaving only a narrow edge for nailing, so that the water, which will run between the joints if the floor is open, will find little surface to remain upon. (Fig. 40.) Sometimes the joists and girders are covered with tarred paper. The roof of the piazza, which is covered with tin, will need especial attention to see that it is given a proper pitch and that the tin is turned up against the boarding of the house wall at least six inches to be clapboarded over. The quality of the tin should be examined and care taken to have it painted on the under side before being laid, and that the joints are well locked and soldered. Blocks must be set on the tin roof and flashed and soldered, to which the balcony posts are to be secured; and where the finish of porch or piazza ends against the house, great care must be taken that the connection is thoroughly flashed with lead.
Fig. 39. Window Frame Outside of Boarding.