The only protection T1-11 siding has against the elements is a coat of paint. Therefore, it is very susceptible to rotting in areas with high humidity levels. If the siding has begun to rot, it can usually be cut out and patched. However, a total replacement is often necessary because it is usually installed without any sheathing underneath it to protect the framing of the house.
First, you need to inspect the damage. Mold, wood rot, and water damage are the characteristics to look for. If the affected area of siding is more than to two to four inches, the next step is to replace the affected panel. In the case of mold, the panel will need to be removed and have a professional inspect and treat the area, preventing the re-growth of mold. T1-11 siding always comes in panels that are easily installed.
If a patch is required, locate two framing studs close enough to the patch. If the area you want to patch is not between two studs, you will need to cut a horizontal crossbeam to hold the patch in place. Use a framing square and tape measure to calculate the correct dimensions. Then, cut a piece with a jigsaw.
Attach your T1-11 patch with four 8d penny nails and apply caulk to all edges of the patch. Administer a coat of primer and paint to match the rest of the siding on your home.