wood
I'm in the process of installing a handrail here and the former owner put these pressure-treated 4×4 posts without cutting them first. They're in the ground already and need to be cut at the correct height to where the railing itself will be attached.
Should I use a circular saw or something to cut from both sides? I already know it won't cut through with just one swipe on one side. Or maybe a good hacksaw or something? Thanks.
2 2x4s are not square, if that matters (3 x 3.5). They will be plenty strong as assembled posts.
Try a traditional lumber yard, they will have untreated pine. Cedar may also be an option.
Your structure would be better supported if you shortened 1 of the 2 paired 2x4s at each corner and made a jack-king stud arrangement like a door frame and header. The main tenant of construction is to bear the weight with structural components and only use fasteners to keep the structure in place, not to bear the load (in shear).
You are, in effect, making a small deck. You should attach the rear 2x8 2x6 to each wall stud. A 4" #10 decking screw would not be too small .
The front and rear members are, in effect, beams and should be 2x8s. The joists running perpendicular to the beam should be 2x6 2x4s hung with joist brackets.
The attached pieces and legs may have exacerbated the effects by not moving with the seat but a piece of pine of that size was probably destined to crack regardless. You can try to weep glue down into it (run a line of yellow glue over the crack then blow it down into the void with an air nozzle) and then clamp out the space but it probably won't be permanent and you could damage your finish with the clamp pressure. Were it me, I'd fill the crack with tinted epoxy and let the piece wear the crack like a badge of honor. Think of a piece reclaimed pine:
Hope this helps, cheers!
Best Answer
It's common practice to set posts and trim them to height later. It's more difficult than you might think to set a post to a perfect height, and you don't always have the angles in advance..
Our strategy was to strike a line all the way around using a carpenter's square, then cut from all sides with a standard circular saw (four sides for level cuts, two for angles, or all four if you set the table angle). Be careful to hit the marks accurately. This leaves you with about a 3/4" square or strip in the center that you'd cut with a hand saw or reciprocating saw.
If you do this carefully there's not much left to clean up. If you miss a bit you'll have some sanding to do.