Page 565 - 2018 National Home Improvement

2018 National Home Improvement Estimator, All Rights Reserved Page 446

Adding a Porch
Figure 16-3 shows how to tie a porch slab to a house with either a conventional crawl-space foundation
(Figure 16-3A) or a concrete slab (Figure 16-3B). Tie the new concrete foundation, piers or slab to the
existing foundation with anchor bolts. The new footing should go at least as deep as the footing on the
existing building.

Figure 16-4 shows construction details for a porch addition built on a concrete slab. In colder climates
and where the porch or deck can be built at least 18 inches above ground level, use conventional floor
framing, as shown in Figure 16-5. Provide a polyethylene soil cover to control excessive moisture.
Whether wood or concrete, slope the floor away from the house at least 1/8 inch per foot of width. That'll
help keep water away from the existing foundation line.