Moisture Control

Checklists for Mitigating and Remediating Mold on Wood Structural Building Components

The following checklists are to be used as a practical guide in conjunction with the information on mold provided in SBCA Research Report 1807-01: “Mold on Structural Building Components.”

Mold on Wood Structural Building Components

This research report seeks to provides fact-based information about causes, effects, and mitigation of mold growth on lumber and wood structural building components. 

Floor Trusses With Masonry Bearing Walls

Question: 

We would like to know if there is a problem with using wood floor trusses with masonry bearing walls without a ledger. Our local supplier has told me that encasing the wood truss in the masonry wall could be detrimental to the truss due to moisture. What, if any, suggestions do you have for this condition? If a bottom chord bearing is used, do the trusses need fire cuts? The two-story building contains masonry bearing walls with wood trusses on the second floor and wood trusses at the roof.

Attic Ventilation

Question: 

I need to put a new roof on my single-family dwelling. The house originally had gable and soffit/eave vents. The roofing contractor suggested that we install a ridge vent when new roof is installed. Should the existing gable vents be blocked off or does it not matter? I have read some debates about whether or not the combination of gable and ridge vents substantially reduces the effect of the soffit vents by having the intake now at the gable vents and exhaust at the ridge. Would this type of ventilation affect the truss warranty?

Proper Storage And Shipping Of Trusses

Question: 

I would like to know the proper storage and shipping of wood trusses.

Lumber Fatigue And Decay

Question: 

What is fatigue in lumber and how does long-term fatigue affect lumber? Does long-term fatigue cause cracks in lumber? What is the difference between long-term fatigue and decay? How do you determine whether lumber has been subject to long-term fatigue or decay?

Lumber Concerns In High Temperature Low Humidity Climates

Question: 

I have been told that the high temperatures and low humidity present in attics can cause deterioration of wood, leading to truss failure. Is this true? If so, what length of time are we looking at and can we see the deterioration in the wood by visual inspection?

Moisture Content Equilibrium And Truss Movement

Question: 

How long does it take the moisture content to stabilize in a wood truss? I live in southern California. Also, how much deflection should be expected in a scissors truss over a partition wall?

Trusses Exposed To The Elements

Question: 

We are having a house built and on a recent visit we brought along a friend who builds houses for a living. He noticed that the trusses were wet and a bit moldy. The wood seemed warped, brown, and had white splotches on it. We are worried that it would later make the roof uneven. How could we tell how long the trusses have been exposed to the elements? What options do we have from here? Do we request new trusses, or can these be repaired?

Allowable Mold Levels For Indoor Air Quality

Question: 

Some questions have been raised regarding the levels of mold in the lumber used in one of our truss projects. The issue of indoor air quality is up and coming. Do you have any information regarding standard allowable values? And how can we test for these contaminants?