8

The strength of the wood beam will depend on the specific species of oak, the grade of lumbar, whether there are any cantilevers, side bracing, and other factors. But 20 ft seems like a very long span for a 4x8. Glancing at some load tables I would say you're in the ballpark of only a few hundred pounds capacity, which is not sufficient when you take into ...


5

Hmmm...no digging in the ground and no concrete. Sounds like the four perimeter beams will be your foundation. They’ll need to be treated for ground contact (pressure treated) as you indicate. Your total load will be about 220 lbs. (Live Load) as you indicate, plus about 800 lbs. in lumber and material (Dead Load). I did not add snow load as I’d assume ...


4

There are too many factors here to give any sort of objective answer: Local climate Tree species Tree health Location conditions Future weather, insects, etc. Ultimately it comes down to your tolerance for risk. A stump of that diameter will remain structurally sound at its core for a number of years, within reason. I'd consider it robust enough to support ...


3

I think those are Simpson Strong-Tie HD3B, or maybe a HD5B. At under 10 bucks a pop, you can probably afford to buy one just to look at it and see if you think it suits your needs. edit: just looked at the fancy $100 ones, and I can see how you get way better attachment from them. I suggest you integrate a strap that ties the bracket to the underside of the ...


2

Not what you asked about, but: connecting two trees with a rigid support is a bad idea. Trees move with the wind and the weather, and you'll get an enormous amount of stress in your bridge during a storm as the trees sway. It will probably damage your bridge, and perhaps the trees as well. If you really want to connect two trees (or a tree and a house), ...


2

At the time of this post you haven't asked a clear question, so I'll offer some general advice. Your design is reasonable except for a few key things: Rigidly attaching such a structure to two separate trees is a sure to result in its rapid destruction. Movement of the trees with respect to one another transfers huge amounts of force to the framing. No ...


2

How much weight can a 3/4" x 8" lag bolt hold when drilled in half way? It's not just about weight but where and how that weight is applied. In your case, it would seem that the how is purely vertical, that is, no tension and applied to the perpendicular grain of the tree. The where is still open. Where on the bolt is the load applied? The further it is ...


1

As requested, The reddish color makes me want to ask if it is madrone, does it shed it’s bark? ,Are the leaves mid size thick or leathery and almost feel waxy? If this is what it is I would not use it for support. Madrone is very hard and cracks and splits easily, it is a large one but I would verify the type before trying to use as it might work for now but ...


1

I see you are using “Dry” lumber (rather than “Green” lumber) so drying out and twisting probably won’t be a problem. However, standard construction practices would require a rim joist. If you follow the Building Code, the Code says, “Joists shall be supported laterally at the ends of joists by blocking, rim joists, etc. to prevent rotation. (See ICC R502.7) ...


1

yes you should use them As you stated they are a part of the lateral system and the answer about that is no you don't need the rim joists here for that reason. However, the rim joists serve other purposes. For one, they are also part of your gravity system. Look at the picture you posted an ask yourself, what stops all the joists from rolling over together ...


1

Do you have to? No. What will happen if you don't? The unsupported ends of your joists will: sag twist The decking on the left of the single tree (from the angle of the picture you provided) will become uneven, making tripping hazards for the occupants up top. You'll also end up needing to replace those deck boards more frequently, since not only will ...


1

Joists crossing on top of beams is much stronger. this is because when joists are butted up to beans they are flexible at the join. I would try to avoid nail lamination in an outdoor location and instead use full-size beams and joists, if the beams must be laminated seal the top to keep rain out of the crack.


1

I agree with the guys above. First 1/4” does not seem at all adequate. Secondly I agree remove the spacers and glue and screw it. But I would say you would def want more solid support under both beams.


1

This is hard to answer without seeing more details about the size/weight of the treehouse and so forth, but I would think that once you bond the beams together the bracket would do the job. I would be more comfortable if there were two holes at each end of the bracket and the bracket were a bit wider (3-3.5") but I think you'll be OK provided that the wood ...


1

The short answer is that no, 1/4" of bearing doesn't have value. Any substantial load would cause the soft SPF lumber you're likely using to shear off. In modern construction you'd be expected to provide at least 3/4" of bearing. Therefore, you're depending on the attachment mechanism between the two joist members. If you were to use a suitable number of ...


1

When your goal is to prevent rot, the best thing is to put those beams tightly together and then seal it all up with construction adhesive, or put a flashing on top of the beam to prevent water getting between the boards. Having a space between the boards will allow tree debris to accumulate in there, and you basically have two separate beams (since they ...


1

Holding everything “up” is not the problem. The stump is taking the load in “parallel grain” direction so it will hold the tree house and half the neighborhood kids easily. The problem is rotation. When everyone runs to one side of the tree house, you’ll have a lot of force wanting to rotate those 2x10’s. The weak link is going to be keeping the tree house ...


1

I'd do a hybrid of your other ideas: Drill through the beam as you would for an eye bolt, but simply feed the cable through and terminate it with a stop of some sort. You could loop back on itself and use a clamp. Back it with a washer to prevent pull-through of any sort. I did almost exactly this with a circular (ring-shaped) suspended treehouse in a huge ...


1

Not too hard -- the page I suspect you got that photo calls it a "hold-down bracket," and that exact part appears to be available here, fastenersplus.com I'll take my finder's fee in chocolate :-)


1

You certainly won't want to just sit the beam in the fork of the tree. The tree will move quite a bit and you'd slowly wear through the bark and damage the tree if you do that. Also note that forks aren't always the strongest part of the tree. What you want to do is have the beam mounted to the tree with hardware that a) allows for lateral movement and b) ...


Only top voted, non community-wiki answers of a minimum length are eligible