I am going to build an 8×8 porch roof with two 4×4 posts as the support, with single 2×8 beams for the front and sides.
Would it be a good idea to notch the 4×4 posts at the top to support the two intersecting 2x8s?
Should I notch 4×4 post for 2×8 porch beams
porch
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Beams typically rest on their posts or trimmer studs. This case is no different, really, and there's no rule that says you have to have a chunk of post running up the height of the beams. I'd miter the beams at a 45 degree angle so that each rests on half the post. Screw them together well and toenail them into the post. It'll look something like this:
8 feet is a typical room height (92-5/8" precut studs with 3 two-by plates), and that's what's normally used for porches as well. Your situation may call for something else, though. It depends on may things.
You seem to have posts at the face of the existing wall. If that's the case, you don't really need to attach the beams other than to hold them in place in a superficial manner.
Otherwise, joist hangers or full bearing on framing in the wall. In either case you need suitable backing structure on which to mount the hangers or bear the beams. If you don't have studs in the right locations, look into top-bearing hangers that you can fasten to the top of your wall plates.
The fact that one beam appears to connect at an outside corner may complicate things a bit. You won't have room for a standard hanger. You might be able to attach around the corner by flattening out one leg of the hanger. That also may be a good location to cut into the corner stud cluster and bear directly.
Best Answer
I understand you drawing. It is not using single point projection, as many of us learnd in drafting. It is OK! IMHO (in my humble opinion) I would not use a 4x4 to sit a front & side rail 2x8 on top of, with no notch (not great) or a notch (worse). If this is for a porch, correct? You are going from a burried concrete pier, or a precast concrete pier, going up 1-3 feet? I would use no less than a 6x6 or 8x8 with no notch. Go to the top of the 2x8's and use at least 3 - 5/8" diameter bolts. No counter sinking either, but use carriage bolts. They have the button top, with a square shank, then the bol. Get bolts 1" longer than you need, only drill to the bolt size. That will require a spade bit with an extension. Using a 3/8 to 1/2" chuck drill. Notching a 4x4 only gives you 2x4 + 2x2 to hang your joists on. With a 2x2 vertical support. I'm a MORE is never wrong, kind of builder. I've been at for 50 years.