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Roof Condensation Issues Impact Building Safety

Roof Condensation Issues Impact Building Safety

Roof condensation is a situation that happens in concrete tilt-up buildings with a panelized roof system.  Moisture often develops in the roof ceiling area and can be trapped there by foil insulation or other types of radiant barriers, causing hidden, and usually major, deterioration of the roof system.  If the moisture build-up is not found and treated, it will slowly destroy the entire building. Depending on when the roof condensation issue is found and how quickly property owners work to get the situation corrected, the cost of repair could be more than $10 per square foot.  If the condensation is found early, however, the repair costs will be far less.

Damage from roof condensation accumulates over many years and will slowly break down a buildings’ complete roof system bit-by-bit, including the framing, nails, and hangers. Usually, this type of damage, or internal rotting, is found when the building is going through the process of a seismic retrofit. It is important to note that this type of building damage is completely preventable. In order to prevent the damage associated with roof condensation, however, commercial property owners and managers must understand what it is, check for it regularly as part of a scheduled maintenance checklist and then treat it correctly as soon as it is found.

So – the big question is this: how does roof condensation usually form?  In most cases, a roof structure contains a vapor retardant. This retardant is a foil radiant barrier, such as R-11-faced fiberglass batting that is attached to the sub-purlins or wrapped around the purlin beams at the underside of the roof structure.  One of the worst scenarios for creating damaging roof condensation is found when batting insulation is covered with foil insulation.

All buildings heat up during the warmer hours of the day.  As the roofing material absorbs the sun’s rays, heat is created in the air pocket between the insulation and the roof. This pocket of air usually reaches considerably warmer temperatures than the rest of the building.  Hot air increases the evaporation of the ambient water molecules, thus pulling moisture into the air pocket.  Because of the insulation, the individual roof cells (the area between the foil and plywood roof) are not vented and therefore they are unable to dry out. As temperatures drop later in the day, the building cools off. As the building cools, the air pockets cool as well and any trapped moisture condenses and spreads throughout the wood roofing materials.  Until this scenario is corrected, the building will go through this condensation process daily.

Typically, a comprehensive inspection is needed to determine condensation damage throughout the roofing structure.  Buildings that have the foil barrier connected or wrapped may have black streaks running down the purlin hangers. There may also be rust weakening the integrity of the purlins and therefore, the structural support of the roof.  It is this type of deterioration that increases the likelihood of significant damage during an earthquake.

In order to begin the necessary building repair in this type of situation, the building must first be allowed to dry out. Peeling back the foil barrier and cutting vents where it joins the purlins is usually the first step to be completed.  Depending on the results of the initial inspection, additional steps may be needed in order to solve the problem, such as replacing wood ledgers and hurricane clips, GLB connections, and re-nailing the roof.  Reviewing the condition of the roof nails is another critical component of the inspection process, however it is a piece that is often missed by many contractors.

Commercial seismic retrofitting provides existing structures with more resistance to seismic activity.  In commercial buildings, a seismic retrofit typically includes strengthening weak connections found in roof to wall connections, shear walls, continuity ties, and the roof diaphragm.  On-going problems with roof condensation are often discovered during the seismic retrofitting process.  It is important to note that repairs can be made through the seismic retrofitting process, rather than scheduling it as separate repair job.

Saunders Commercial Seismic Retrofit can provide a thorough, all-encompassing inspection of any commercial building, based on many years of preventing and repairing roof condensation problems. Having such a complete inspection and investing in a seismic retrofit will ensure the safety and security of your commercial property.  If you would like to have a full understanding of any potential roof condensation and repair issues, or if you are considering a seismic retrofit for your commercial building in southern California, call Saunders Commercial Seismic Retrofit Los Angeles today!


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(949) 646-0034

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