Engineer Interview: Melinda White on Florida Structural Claims

Thank you to Melinda White, our structural engineer in Florida, for this interview!

Q:  Has there been a common theme/cause of the claims you have been looking at? If so, what?

A: Nearly all of the roof claims I have observed recently have addressed the question of sustained weathering versus storm event damage.  In central and east-coast Florida we see long-term roof deterioration due to ultra-violet radiation, salt, wind and biological damage as well as storm and hurricane damage.  Homeowners are routinely surprised that the 20 or 30 year roof that they installed 10 years ago has failed.  Naturally, they assume that recent storm damage – and there has always been a recent storm! – has caused the failure of the roof that would otherwise last another 10 to 20 years.  Typically I find this assumption to be false.  Weather conditions in Florida wreak havoc on roof cladding of all types.

Roofs with little or no shade from adjacent trees or structures bake from both sides – from above via direct sunlight on the cladding and from below via high temperatures in the attic.  Temperatures range 30 to 40 degrees above ambient temperature in attics below the typical asphalt shingle in this area.  When average high temperatures stay above 90 degrees for months in Florida, this represents months of attic temperatures that reach above 120 degrees!

Roofs with abundant shade have dramatically different problems.  Insects, lichen, moss, and algae thrive on roofs that stay moist due to abundant shade.  I have observed roofs with abundant shade in one area showing damage from biological sources and no shade in another area that shows advanced stages of buckling and cupping associated with prolonged exposure to the elements.

The final straw for many of these roofs is a storm event.  Summer storms in Florida pack a powerful punch.  Structures close to the ocean as well as those adjacent to lakes and ponds are particularly vulnerable to wind damage.  Sustained wind speeds in excess of 60 mph are common as fronts of storms pass through the peninsula of Florida.  The winds, packing the punch only moisture-laden sea-level air will, accelerate across flat smooth surfaces like the ocean, lakes and ponds to pound adjacent structures.  Significant, repetitive uplift forces fatigue shingles causing the early failure of roofing systems.  Winds scour granules off shingles leaving them even more vulnerable to ultra-violet radiation.

Q: Do you at times provide repair/design recommendations for the claims you have investigated?

A: Repair recommendations are frequently requested by our clients.  Determining the proper repair for the damage observed is the most challenging and exciting part of what I do.  I answer questions like:  How much of the structure of the roof has been compromised by a lightening strike?  Has the roof structure been affected by the vehicle impact to the wall?  How do we repair a slab that is sinking within an exterior wall structure that is un-affected?  Is a partial or full roof replacement required for a damaged roof?  Each claim has a unique timeline, history and subsequent repair recommendation.

When I observed a recent lightening strike, the repair recommendation included the area directly surrounding the strike as well as localized areas surprisingly distant from the strike where damage was observed.  The repair in close proximity to the strike included removal and replacement of the roof including the rafter beams.  Repair to the more remote damage roof included sistering the damaged structure with new lumber and limited replacement of the roof sheathing and cladding.

A recent vehicle impact claim required repair recommendations that included repair to an un-reinforced concrete masonry unit (CMU) wall and a traditionally wood framed wall, but did not require repair to the adjacent roof!

A water line leak leading to soil loss under the slab was the culprit in a recent claim.  In this case our client needed a repair recommendation that allowed the family to remain living in the home while slab repairs were completed.  In this case the exterior structural walls and roof were unaffected by the soil loss.  The concrete grade beams and strip footings were spanning the voids left by the soil loss.  Our repair recommendation was specifically designed to re-level the slab on grade without causing uplift on the exterior footings and load bearing walls.

Q: Any of the claims investigations that are of particular interest?

A: Pie was retained to ascertain the cause of damage to a home where the homeowner discovered shingles, one or two at a time, in the yard of the property and reported water staining in a second story bathroom.  My conclusions on this claim were that the water intrusion resulted from a damaged shingle above an attic vent.  The vent flange had not been flashed during initial construction and installation.  In this case the 17 year old roof covering was failing due to advanced weathering.  Recent storms had caused additional damage to the roofing system.  The roof was at or near the end of its service life and significant partial roof repairs would likely damage the roof system further.  In this case the repair recommendation was to remove and replace the existing shingles, underlayment, roof penetrations and flashing.  I created a chart showing our client the extent and approximate age of the damage due to wind, weathering and mechanical causes.

I observed another interesting claim where the homeowner reported peeling paint, hairline cracks and water staining on the ceilings of several rooms throughout the building.  In this case, the roof covering was in good repair, the roof penetrations were properly flashed and were not leaking.  Detailed observation revealed that the water infiltration into the ceiling system was a result of condensation occurring on the supply ductwork in the attic.  Repair recommendations on this claim included pressurized HVAC testing to ensure the air tightness of the duct joints and connections.

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