Number of posts needed to support porch roof?

Question

I would like to add 20 ft. partial porch (think craftsman style, a shingled half-wall instead of railings). How many columns are needed to support this span?

Answer 1

Not much information - how far out does the porch project  8'-10'-12'?  The span on your porch posts is determined by the weight load of the roof.

We just completed a beer garden addition with a single sloped roof. It was 16' wide x 40' long. Our main support posts are 8' on center with a 2" x 10" on the inside and outside of the post at the top, and a double 2" x6" top plate.

The inside and outside 2" x10"s at the top form a box header that carries the weight of the roof between the posts.

Answer 2

I have a 30' porch and have 6 posts.   They are 4"X 4". So you would need about 5.

Answer 3

The number size  & spacing of the suports depends entirely on the depth / strengh of the header spanning them.

Just as an example, have an open porch approx 40' long & 8' deep supported by 6, 4"x 4"x 8' posts & the "header" is doubled up 2"x 8" s w/ a max span of about 10'.

Told that each post is good for approx 1000 lbs .

The structure was OKd & takes into account expected snow loads.

The American Wood Council site has figures for  beam sizes

for loads over length of span.

Going to need a permit, so you or contractor must  submit a design to the building inspector & see if it meets local codes .

Best regards