mushrooms in Hardie plank

[Ken Meyer]

Has anyone seen mushrooms growing out of Hardie plank? This was a first for me. This is on the gable end of a garage, south side. Most of the butt joints have been recaulked, the house is 8 years old. From the garage attic, I do see some water stains on the roof sheathing at the peak. The mushrooms are growing out from lower down, about 18 to 20 inches off to the side below the peak. The OSB looks fine from the garage attic, no staining at all or other signs of moisture. I would think that if mushrooms are growing in the OSB, there would be more evidence.

My moisture meter placed right next to the mushrooms picked up only a slightly (2 per cent) elevated reading compared to the rest of the siding in that area. Of course, it's nice and dry now.

Can the mushrooms be growing out of the siding? I can't really tell where the water is coming in, my best guess is wind driven rain getting in under the shingles or around the flashing at the peak. I couldn't stick around too much when trying to get a closer look at the peak, there were two yellow jacket nests under construction right behind the barge rafter, but I did get a couple of pix before being driven back down the ladder.

Click to Enlarge

40.12 KB

Click to Enlarge

43.16 KB

Click to Enlarge

53.32 KB

[Richard Moore]

Looking at the color of the area just above the mushrooms as well as the way the filler appears to have been scraped, rather than squeezed, into the gaps, I wonder if they used some interior grade wood filler, rather than an exterior grade "caulk". That might be what the fungi is feeding on.

[Bob White]

I'm guessing that water is running down the siding, hitting that horizontal surface just below the fungal area and wicking back into the OSB sheathing.

The same kind of thing happened below, where a horizontal trim board directed water to the siding seams. Lots o' rot...

Click to Enlarge

50.44 KB

[Ken Meyer]

I think Richard is onto it. His theory explains why the OSB still looks good. Mushrooms are just the fruiting bodies of the fungus, which has to have been there awhile before the mushrooms sprout. The OSB would show evidence if it had been wet for years. Here's a closer look.

Click to Enlarge

28.53 KB

[SWagar]

Ken,

I found the same type of thing a couple a years ago. The fruiting bodies were coming out of the siding joints in three or four places. As I recall, I recommended that the siding be removed and the area inspected for water damage .... and so on. I was pretty sure that there must have been trapped water and fungus behind the siding. Unfortunately the buyers must have thought I was on drugs because they didn't want to have a investigation or repairs done, they just took the house the way it was.

Click to Enlarge

27.13 KB

[Ken Meyer]

Too bad, I'll bet you would have liked to know what they found. I'm going to ask the buyer to keep me posted on what he finds, he may or may not.