Affect of mold on strength of wood joists and sheathing
Affect of mold on strength of wood joists and sheathing
(OP)
I inspected a house yesterday where we were being asked to issue a report "on the subfloor" of the house. Once I arrived I understood what they were talking about. The floor was spongy underfoot in several areas. From the basement I saw areas with fungal growth and discoloration on the bottom of the floor sheathing and floor joists. The damage was visibly extensive to the sheathing and I would recommend replacing all the sheathing. My question is regarding the 2x10 joists. They spanned 13'-6" which was ok, but many had fungal growth on the sides of the members. I didn't have a moisture meter on me so I don't know what the moisture levels in the wood wood. There was no section loss at the surface so I don't believe the strength of the joists was compromised. There was one area under the bathroom where deteriorated joists were observed and that was probably from a water loss (the house was vacant).
Has anyone come across this, and if so what's your experience been with joists like this? replacing them is a signifcant undertaking. I think I would recommend cleaning the fungal growth from the existing joists and sistering new joists to the existing where required. You'll also see in the pictures I attached that the joists are notched at the bottom, those will have to be replaced as they do not conform to code.




Has anyone come across this, and if so what's your experience been with joists like this? replacing them is a signifcant undertaking. I think I would recommend cleaning the fungal growth from the existing joists and sistering new joists to the existing where required. You'll also see in the pictures I attached that the joists are notched at the bottom, those will have to be replaced as they do not conform to code.










RE: Affect of mold on strength of wood joists and sheathing
Concerning your question, mold and fungus being present on wood usually is not a structural problem. See Chapter 14 of the (free) USDA "Wood As An Engineering Material".
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RE: Affect of mold on strength of wood joists and sheathing
You can lose 15% of the material strength without any loss of weight with brown rot. By the time it is visible, you can have significant loss of strength.
Is the basement damp and humid?
Dik
RE: Affect of mold on strength of wood joists and sheathing
RE: Affect of mold on strength of wood joists and sheathing
RE: Affect of mold on strength of wood joists and sheathing
Dave
Thaidavid
RE: Affect of mold on strength of wood joists and sheathing