Porch Beam/posts Question


Old 11-07-13, 01:58 PM
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Porch Beam/posts Question

Hello! I'm new to the form and came for advice. I'm finishing the exterior on a home I started to build last year. One of my last projects is the porch. The porch is 52' long and 6.5' in depth as it spans the length of the house. The porch is covered by the roof trusses that were designed to cantilever without needed structural support from beams or post. We would like to add a beam (52') with 5 posts just for aesthetics. The beam and post will be stained to match the garage doors and front entry door so we want to go with cedar wood. Since these are not structural what is the best way to frame a false beam instead of using solid cedar beams. Besides weight, the cost is more than I want to spend.

We are thinking an 8"(w) x 10"(h) beam supported by the 5 (8") posts. My initial thoughts were to frame a skeleton beam out of 2x4 and cover with 1" cedar lumber for the beam. The post would be made of 2x6s stacked and wrapped with cedar lumber as well.

Thanks for any advice you can give...

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Old 11-07-13, 04:19 PM
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I would probably try and use 1x12 for the beam sides and try to not have to rip it. Your beam height should be close to 11 1/4" that way.

You would probably want to start by pre-building some short sections of wall, out of 2x8. I would build it like a short wall with a single top plate, a single bottom plate, and 7" long studs, 24" on center. Shoot that all together... Snap a chalk line along the entire length of the bottom of the trusses. Then shoot those sections of wall up, toenailing the top plate to the bottom of the truss. Once those sections are up, install 7/16" or 1/2" OSB or plywood to both sides, staggering the plywood seams with the wall section seams to tie it all together.

By adding 1/2" to both sides of framing, it makes the framing width 8 1/4" x 10". By the time you cap the bottom with cedar, the beam height will be 10 3/4". Letting the cedar sides hang down 1/2" lower than the piece on the bottom of the beam will probably save you some headaches, and also provides a drip edge, should it get wet. That brings us to 11 1/4", which is about the width of a 1x12. (to give you an idea of materials cost... a single 1x12x16' cedar is $51.46) Cutting the bottom piece of cedar maybe 1/8" wider than the framing (8 3/8") will compensate for some weave in the framing and should allow you to install it fairly straight, even if the framing isn't perfect. When you add 3/4" thickness of cedar to both sides you will have 9 3/4" of width. A 7 1/2 x 7 1/2" post / column will fit under that beam with some room to spare, since it has to fit between the sides of the beam (which I'd make lower by 1/2"), and the bottom of the beam is 8 3/8" wide.

If all that sounds too beefy, scale the width back by 2" so that a 6x6 rough sawn post will work. (6x6x16' = $101, and are actually 6" x 6", not 5 1/2 x 5 1/2.)... quite a savings, usually good quality and still beefy looking.

The top of the beam wall will be just as straight as your chalk line is, but I think the problem you may have is finding lumber that is straight enough (or stays straight enough) so that the bottom of the beam doesn't weave around.

Now as for the posts / columns, I would really try and talk you into using solid 8x8 cedar posts. I just checked the price at Menards and they are $234.00 for 16' lengths. Unless your post height (from below the beam to the floor) is more than 8'... creating a lot of waste... I would say that's a bargain, compared to the time and materials in building a beam. The cost of building an 8' long beam using the method you suggest would be: $15 for 3 2x6's... and $54 for 3 1x10x8 red cedar. So you'd have at least $69 in materials vs $117 for a real solid post ($50 if you went with the rough sawn 6x6!). I would also suspect that the quality of the 1x10 will not match the quality of either a 6x6 or 8x8. And you will have joinery issues with the 1x10's unless you fit them loosely around the framing, then glue with construction adhesive and finish nail (stainless steel 7d's) generously. All the nail holes will be unsightly. If you use 6x6 or 8x8... no nail holes and no joinery issues. And it would be a LOT faster.

So I guess if you wanted an opinion, I'd make the beam at least 9 1/4" high if you went with the rough 6x6 posts. If you go with 8x8 posts, I'd make the beam 11 1/4" high. The bottom width of the beam will be dependent on the post you choose, obviously. I don't think the 6" posts would look too small, but you can see it, I can't!
Old 11-21-13, 10:17 AM
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Thanks for the tips! I hole to get started next week over the Thanksgiving break.


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