Lessons from Dorian – Exterior Details for Coastal Homes

Dorian_2019


Details Matter


by Doug Millen

This past September I vacationed on the Outer Banks of North Carolina. A location that is known for its bad weather. As can be expected during hurricane season, our vacation was delayed, by Hurricane Dorian. After 3 days of waiting, we were finally allowed to enter this storm-ravaged area. We drove through standing water and washout roads to our rental home. During our stay, I was able to observe the exterior of many buildings that received damage from Dorian. We enjoyed our stay in the only rentable house in the culdesac. Below are my observations and recommendations as a coastal builder on “DETAILS THAT MATTER”.

Roofing & Trim Damage

Roofing & Trim Damage

Roofing:

  • Sheathing – 5/8 plywood held up better than 1/2″ and better than OSB. Extra nailing at eaves and rakes helped keep the sheathing in place. The thicker plywood also held the roofing nails better.
  • Underlayment – Water & Ice saved damage to many homes where the shingles were blown off. Buildings with only tar paper or no paper at all did not far so well.
  • Roofing – Wood shingles and 50-year asphalt shingles held up the best. Lighter weight shingles did not. Always use 6 nails per shingle (hurricane nailing) when nailing asphalt shingles in these areas. Shingles on the lee side took the most damage due to the uplift of the wind traveling over the ridge. Also, double nail all ridge caps.

Exterior Trim:

  • Roof Trim – Never use Vinyl or Alum. trim. Almost every home with this type of trim lost it when Dorian passed offshore. Solid wood or PVC trim is a better choice.
  • Window Trim – Poor flashing and details at the bottom of windows over time caused rotted sheathing behind the shingles that lead to the nails failing and shingles blowing off. 

Doors & Windows: 

  • Most doors & windows are no match for hurricanes but the Andersen windows I observed did a great job of keeping the bulk of the water out. Only windows on the storm side showed signs of where water had entered. By the look of the stained wood, this probably happens several times a year. This is typical for coastal homes, plan accordingly. We recommend Marvin or Andersen windows with the sea coast hardware package and impact resistance glass for coastal homes.
Rotted sheathing and framing under windows

Rotted sheathing and framing under windows

Siding:

  • Course spacing on the shingle siding of 4″ held up better than 5-6″ coursing. Cheep, untreated shingles weathered thin quickly and readily blew off. Pre-Stained or higher grade shingles held up better and protected the home. Tyvek and tarpaper are inadequate. Use a high-end weather barrier under siding such as Blue-Skin to protect the sheathing, insulation, and interior.
  • Wood Clapboards, vertical wood siding over 4″ and Vinyl siding are a poor choice. Wood shingles work perfectly in this environment.

Decks & Porches:

  • Footings – Posts need to be tied to the footings, beams, and joists above. Not with just nails but with bolts and metal straps.
  • Stairs – Stairs to grade should be able to lift up above storm surge during these events.
  • Concrete Slabs – The edges of on-grade concrete slabs (i.e carports) should extend far below grade to prevent the undermining of the slabs from the wave action during the tidal surge.

Foundations:

  • Raising the living area above the tidal surge works well. Pilings of pressure-treated lumber are easy to put in place and work.
  • The Lattice used below the living areas should be easy to replace and not create hazardous debris during tidal flow. Bigger spaces between lattice should be considered.

The Bottom Line

Use heavyweight materials when possible. Extra nailing is a must. Water under wind pressure will find any weakness in your system, and water will run uphill. What you can’t see in the finished product, often matters the most. Pay attention to the construction details for a job that “Stands the Test of Time”.

Doug Millen
President
Bay View Builders