Replacing Barge Boards

[stardelta]

I want to replace my old wooden barge boards with exterior 18mmm Ply.cut down from a 8x4 sheet.Problem is the length required from gutter to eaves is about 10'. Where is the best place to make a joint and what do I do to make a good job ?

Thanks

[buildersmate]

I assume you mean the ridgeline to the gutter is 10 feet? - although that sounds very small, even for a cottage. The bargeboards are the angled pieces that run between the gutter ends of the fascia up to the apex??

If so, the bargeboard will invariably be nailed onto the end of a timber structure fabricated onto the masonry gable end, adjacent to the last rafter. Once you've taken off the existing bargeboard, you will be able to see where you have timber behind on which to nail.

[The Builder]

You're going to get a "butt joint" there, Stardelta. Not terribly pretty, and difficult to hide.
Rebating the butts would help, but it would still leave you with a fine line which will move and crack eventually.
To help, glue the butt ends with carpenter's polyurethane glue. It's immensely strong, and should help to make the whole barge a little more stable.
Have you considered alternative materials?

[johnk]

I think you would be better with plastic. The ply will delaminate fairly quickly unless you use marine ply which is very expensive