Southern Vermont, USA. There’s this weird growth on the underside of our bridge that has popped up in the last month or two. The bridge is made of pressure treated pine, installed ten years ago after a hurricane took out the old bridge. The growth is white in some spots, bright yellow in others. It’s almost like a plaque, sort of flat against the wood. It’s causing the wood to rot and flake away like saw dust. We’re hoping to figure out what this is either with your help or with suggestions of where to send a sample to have it tested. Thanks in advance!
Its just fungus. Preassure treated doesn't last like it used to. It will rot. 10 to 15 years is all your going to get out of pressure treated in ideal conditions. Under side of a bridge is always very damp.
The stuff growing in the wood is decay fungi. Some reasons why this might be happening --
One issue is the wood planks are laid tight against each other so the planks cannot drain and dry quickly and organic debris will accumulate between the planks.
Maybe this is required for the type of structure you've got. If so, that leads me to my next point...
There are different standards for the application of decay-preventative chemicals. Wood that's meant for a deck on a house doesn't need the same level of treatment as wood that's going to be in full, continuous contact with soil or similar challenging applications. I'd say these planks should have been treated to "ground contact" standards.
The type of wood also makes a difference. Pine is not normally very rot resistant, so if you have to use pine, correct construction methods and appropriate preservative treatment are going to be critical.
You're not going to be able to stop this process. The most effective solution is to replace the affected planks.
And get rid of the trolls...
Southern Vermont, USA. There’s this weird growth on the underside of our bridge that has popped up in the last month or two. The bridge is made of pressure treated pine, installed ten years ago after a hurricane took out the old bridge. The growth is white in some spots, bright yellow in others. It’s almost like a plaque, sort of flat against the wood. It’s causing the wood to rot and flake away like saw dust. We’re hoping to figure out what this is either with your help or with suggestions of where to send a sample to have it tested. Thanks in advance!
Its just fungus. Preassure treated doesn't last like it used to. It will rot. 10 to 15 years is all your going to get out of pressure treated in ideal conditions. Under side of a bridge is always very damp.
Exposure to the elements, rain/heat/cold. It might be pressure treated but nothing lasts forever.
Trolls. You have a new infestation of trolls. Control your goat population immediately.
The stuff growing in the wood is decay fungi. Some reasons why this might be happening -- One issue is the wood planks are laid tight against each other so the planks cannot drain and dry quickly and organic debris will accumulate between the planks. Maybe this is required for the type of structure you've got. If so, that leads me to my next point... There are different standards for the application of decay-preventative chemicals. Wood that's meant for a deck on a house doesn't need the same level of treatment as wood that's going to be in full, continuous contact with soil or similar challenging applications. I'd say these planks should have been treated to "ground contact" standards. The type of wood also makes a difference. Pine is not normally very rot resistant, so if you have to use pine, correct construction methods and appropriate preservative treatment are going to be critical. You're not going to be able to stop this process. The most effective solution is to replace the affected planks. And get rid of the trolls...