Going over the old cedar siding is something I would not advise
There are a number of reasons Here are a few main one
1.If there is any rot or water/weather damage you are leaving a “soft” spot in your home which is also a perfect spot for insects to nest
2. Your T-111 should be nailed to the framing ie; through the plywood and into a stud this will hold the T-111 tighter to the house and have less chances of warpage over time Plus you would have to use very long nails to go through the T-111,the old ceder,the plywood sheathing and into the studs
3. Last but not least you will have a big suprise when you see that the new T-111 sticks out way pass all your trim at the doors and windows.
Going over the old cedar siding is something I would not advise
There are a number of reasons Here are a few main one
1.If there is any rot or water/weather damage you are leaving a “soft” spot in your home which is also a perfect spot for insects to nest
2. Your T-111 should be nailed to the framing ie; through the plywood and into a stud this will hold the T-111 tighter to the house and have less chances of warpage over time Plus you would have to use very long nails to go through the T-111,the old ceder,the plywood sheathing and into the studs
3. Last but not least you will have a big suprise when you see that the new T-111 sticks out way pass all your trim at the doors and windows.
Hope this helps … Good luck
dubiewon nailed it. I completely agree with his answer.