Comming Soon - New front porch!

[toxic111]

The 2x6's for your joists @ 10' span will be fine, yes the 15" centres is odd... I would be surprised it works out better than 16"o.c. since you will get an end every 4' (e.g. 4', 8', 12', etc.) unless you are going with 10' long decking, then that will work out perfect.

As for your rafters, on that same 10' span I would go 2x6 over 2x4 just to prevent any sagging (the 2x4's will sag over 10' just from thier own weight)

I also saw that you are planning on using a chainsaw for cutting the 4x4, I would jsut use the skilsaw for that, it will give you a much better cut, just square it off, and make your first cut, then flip it over to make the second cut.

Oh FYI, my experience & job is in construction & design, residential and commercial, over 20yrs worth.

The only other item is to make sure if you need a permit or not, most areas if you are building anything bigger than 10'x10' you will need one, it will save you a lot of grief later.