Do I replace or repair rotted board in 100 year-old house?

Question

I have removed plaster and lath on the inside of an exterior wall of a 100 year old house in preparation for spray foam insulation. Two of the boards are partly rotted. See pictures. Everything else is dry and solid. Exterior brick was replaced many years ago. The gaps between the boards make it seem like I could take these two out and replace them. Alternatively, I could attempt to repair them with epoxy although they are pretty far gone. Any suggestions as to what I should do would be greatly appreciated. This is the top floor apartment of a three-story triplex. I am very reluctant to remove the boards as this may have implications for the brick wall behind it. Does it make sense to brace the boards above and below the weak ones with metal and screws after removing any rot and leave it at that?

Did I miss another pic, or are my eyes deceiving me? What I am seeing looks like a bit of mold on a piece of wood. I cannot see any rot or decay. — RMDman, Jun 28 '23 at 18:10
I added pics. The spongey part in original pic can be removed by hand. — matt in Montreal, Jun 28 '23 at 19:53
"*Everything else is dry and solid.*". Does that imply that the rotted wood is not dry? — Ray Butterworth, Jun 28 '23 at 21:04

score 2 · Answer 1 · answered Jun 28 '23 at 17:17

Repairing rotted wood involves removing the rotted parts first, then filling the resulting gaps with epoxy.

From:

they are pretty far gone.

I gather that what's left of the pieces after the rotted parts are removed is rather small. So a complete replace seems the more logical solution.

score 1 · Answer 2 · answered Jun 28 '23 at 17:20

Rotted wood is usually a replacement job.

Cut all rot out plus a few inches.

Make sure any leaks that caused the rot have been fixed.

As these boards might be sheathing for the brick wall, and have anchors for the bricks replacement might be more tricky.

Do I replace or repair rotted board in 100 year-old house?

2 Answers2