Hello,
I need to replace my roof as it is over 20 years old and wanted to extend the roof overhangs at the same time.
My roof currently has 3/8 plywood sheathing (yes, I confirmed this) and I wanted to replace it with 5/8 sheathing. Someone told me that I could put 5/8 sheathing over the 3/8 sheathing so I don’t have to worry about the taking most of the 3/8 plywood off and would have a total thickness of 3/4.
I am thinking about using 3/4 around the perimeter of the roof where I would be extending the overhangs so the 3/4 inch would tie back into the roof for support, then would add 5/8 on the remaining roof so it would equal 3/4 as well.
Is this advisable or should I just remove everything and put 5/8 on the entire roof?
Thank you for your input on this.
Replies
j,
how far do you want to extend the overhang? You can't just rely on the plywood hanging off the end of the rafters to be structurally sound.
and, 3/8 +5/8 is an inch. You got me confused with the fractions. Lemme read your post again?
the span between the rafters generally dictates the thickness of the sheathing used
Yea, after reading my own post, I agree the math is wrong. I should have read it twice...Sorry about that.
Anyway, I figure I will just remove all the 3/8 sheathing and replace it with new 5/8. I have attached a picture of the overhang drawing for one side of the house. I plan to sister the eaves and use ladder type extensions for the gables. The eaves have an existing 6” and I will add another 16” including the fascia board for a total of 22”. The cables currently have zero so they will be 22”. Should I tie the ladder extension to the existing rafters or would the 5/8 sheathing hold it?
Thank you
I've never been all that excited about simple ladder extensions on the gables. I've seen it tried and I've seen it fail. Of course, tying back to the roof framing in a retrofit situation is not a simple task, so I guess I wouldn't discount the approach entirely.
Outlookers
In California, we install outlookers on gable ends. Wth truss framing the outlookers are 2x4s laid flat and notched in to the top chord of the gable end truss. (It's ok to cut this if it is not bearing.) They go back to the first common truss where they are face nailed. The fascia is nailed to the ends. Usually 48" oc to catch the plywood edges. If you are using starter board it runs perpendicular to the outlookers. If you are removing the existing sheathing this should work for you.
Aside from your arithmetic being wrong, you can't simply hang plywood off the edge of a roof and expect it to stay for years where you put it without sagging. You might get away with doing a 6 inch overhang, but not much more, unless you use something better than standard plywood.
You need to explain your plans better -- What is the rafter spacing? How much of an overhang are you talking about adding?
Roof sheathing
You might get away.