FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

13 CONSTRUCTING THE BUILDING Volume II
Avoiding assemblies that form “buckets” and retain water adjacent to wood.
Avoiding designs that result in ledges below a vertical or sloped surface. Ledges collect water quite
readily, and the resulting ponding from rain or condensation alternating with solar radiation causes
shrink-swell cycling, resulting in checks that allow increased water penetration.
To the extent possible, minimizing the number of vertical holes in exposed horizontal surfaces from
nails, lags, and bolts.
When possible, avoiding the use of stair stringers that are notched for each stair. Notching exposes the
end grain, which is then covered by the stair. As a result, the stair tends to retain moisture at the notch
where the bending stress is greatest at the minimum depth section. Figure 13-12 illustrates stair stringer
exposure, and Figure 13-13 shows the type of deterioration that can result.
Figure 13-12.
Exposure of end grain in
stair stringer cuts
Figure 13-13.
Deterioration in a notched
stair stringer
13-16 COASTAL CONSTRUCTION MANUAL