Roof-to-Wall and Deck-to-Wall Flashing
Home Builder’s Guide to Coastal Construction
FEMA 499/June 2005 
Technical Fact Sheet No. 24

Purpose: To emphasize the importance of proper roof and deck flashing, and to 
provide typical and enhanced flashing techniques for coastal homes.

Key Issues
--Poor performance of flashing and subsequent water intrusion is a common 
problem for coastal homes.
--Enhanced flashing techniques are recommended in areas that frequently 
experience high winds and driving rain.
--Water penetration at deck ledgers can cause wood dry rot and corrosion of 
connectors leading to deck collapse.

Roof and Deck Flashing Recommendations for Coastal Areas
--Always lap flashing and other moisture barriers properly.
--Use increased lap lengths for added protection. 
--Do not rely on sealant as a substitute for proper lapping. 
--Use fasteners that are compatible with or of the same type of metal as the 
flashing material.
--Use flashing cement at joints to help secure flashing.
--At roof-to-wall intersections (see Figure 1):
--Use step flashing that has a 2- to 4-inch-longer vertical leg than normal.
--Tape the top of step flashing with 4-inch-wide (minimum) self-adhering 
modified bitumen roof tape.
--Do not seal housewrap or building paper to step flashing.
--For deck flashing:
--Follow proper installation sequence to prevent water penetration at deck 
ledger (see Figure 2).
--Leave gap between first deck board and flashing to allow for drainage (see 
Figure 3).
--Use spacer behind ledger to provide gap for drainage (see Figure 3).
--Use stainless steel deck connection hardware.

See Fact Sheets Nos. 19 and 20 for rake and eave details.

Figure 1. roof/wall flashing detail.

Figure 2. Installation sequence for deck ledger flashing. Five steps. 

Figure 3. deck ledger flashing.

[End of Fact Sheet No. 24]