12×10 treehouse – any issues with the final draft of these framing plans?
I’ve attached wall plans for this treehouse after going through multiple iterations and asking various questions and doing a lot of reading; however, I wanted to get a final check on if any potential issues or recommendations.
The goal is to ensure this is strong with respect to shear as well as lots of people going on top of it; however, the plan is to be extra cautious and not allow people in it during wind events or potential wind events.
Based on feedback I received in this forum, I’m planning to do interior sheathing too to add extra shear strength.
This is located in the lowest seismic zone in the 48 states but could have very rare tornados. If there were to be a tornado, all bets are off on it surviving, but the desire would be that it would be able to handle any normal gusty winds.
The following isn’t part of the question, but is included since I know sometimes people are curious about the additional details:
The platform which this will be attached to is 16×12 and the treehouse will go the full width on the shorter dimension. The platform is comprised of 2×12 joists with blocking, rim joists, and hurricane ties on the fixed end (it’s a 2-tree setup so the opposite end has UHMW sliding plastic between the joist bottoms and the spreader beam they rest on). On top of the joists are 5/4 deck boards. Both joists and deck boards are GC treated. The platform sits on top of two 4x6x12 spreader beams with two 4×6 45 degree knee brace supports each. These beams and their knee braces have 3 total GL / TABs each which are rated for something like 8,000 lbs per bolt (they are 1-1/4 steel diameter with a 3-in steel support collar).
Thanks
Replies
It looks like you have a very substantial structure there. I would say only that since there are 2x12 headers over the windows, you might want to beef up the framing over the door.
You could double the rim joist over the door for example and put hangers on the first few joists.
Also, just make sure the stud layoff is correct. The first stud and joist should be 15.25" from the corner and "set ahead". This will make your sheet goods work much better.
Interesting idea adding strength by the door. Is that because you think I might need that amount of strength or just to be more in keeping with what you saw elsewhere? The 2x12 headers were more out of convenience given that's the desired window height anyways so not making small cripples, rather than because I thought I'd need that much strength if that affects your take on it.
Btw, today someone else suggested I add a slight slope to the roof (like 1/8" per ft or 1/4" per ft). I'd do this by making the 10ft walls barely angled at the top and thus have the studs vary ever so much in height. To keep the one window rough opening square, I might rip its header to that slope. I'm thinking of going with a 1/4" per foot for better runoff. Any thoughts on that?
Thanks
My suggestion was based on the window headers. I suspect the door will be fine.
As for the roof, I'd put the slope in the joist/rafters rather than messing with the walls. You can up the joists to 2x10(or12) and cut a taper on them.
I think you have a few extra studs where you do not need them.
You might want to put extra blocking near the end of the joists over the door to help stiffen and spread the loads to the sides of the door.
What are your plans for finishing the 3/4 inch plywood over the roof? What kind of railings are you going to install?
Yeah, definitely some extra studs in there - where I've added them for spacing convenience purposes, should I just use scrap 2x4 pieces instead? I saw a FineHomeBuilding framing video today where they did that.
What are you thinking I should do with regards to adding the extra blocking near the joists over the door since there will be a rim joist parallel to / over the door?
For finishing the 3/4 plywood, blocking being added to be able to screw all edges, plus h-clips. Then on top of that Grace Ice & Water Shield self adhesive underlayment (model #5003002). On top of that will be low-slope roll roofing (currently planning on GAF Liberty 3730900 from Home Depot), and then on top of that Henry Tropi-cool #887 silicone roof sealer with some sort of sprinkled granules for traction. Though now that I'm doing a 1/4-in-12 slope, perhaps I forego the Tropi-cool and just do the other stuff.
For the railing the current candidates are 4-ft high plexiglass (though maybe with a gap to allow wind through) plus some vertical (and potentially horizontal) wood supports for it on the outside side, or perhaps 4 or 5 ft vertical bar iron fencing panels instead. (I'm probably more cautious than most people in this regard but with the heights in consideration I don't want to take chances with accidental injury or death).
Thanks
The rim joist ability to spread loads among the joists will be limited to the nails used.
Solid blocking between the joists will be better (and in my suggestion, in addition to the rim joist)
You could also double up the rim joist and use joist hangers on the joists over the doors and windows.
I think your idea to slope that roof is a good one.
For the railing, given the amount of sail area hanging in the tree, you might look at a cable solution. There are also aluminum options that would weigh less than iron fencing.
Keep in mind that that roofing is not designed to be walked on. In hot, sunny weather, the granules might tend to pick up on shoes. The leafy tree might mitigate that somewhat.
That makes sense - I was thinking of transferring the load in a different way.
Good call on aluminum fencing to make lighter and about the plexi being too much of a sail - maybe I'll use it on a very limited basis and then aluminum the rest to compromise between viewing and surface area.
Very interesting note on the cable railing - I had ruled out cable because horizontal would let a smaller kid climb up easily but I hadn't thought about vertical cable solutions. The vertical stainless steel cable railing kit at Home Depot looks decently priced.
For roofing maybe I'll end up putting an outdoor rug up there on top of the roofing material in light of your comment - might help provide a nicer surface to hang out on too.
Thanks!
You can also look at treating that roof like a boat deck. fiberglass and resin topped by boat carpet or smooth covering.
Interesting idea - is there anything unique about a structure that would cause this to run into issues down the road? I'm thinking not but thought I'd put it out there. It sounds like a solid idea.
The only big worry is impact damage. branches fall from trees. But you can fix this. another is if the deck is wet or dirty when you put the coatings on.
https://fiberglasssite.com/ These folks have lots of info. Might even skip the boat flooring and just put a texture in the fiberglass coating
You also can buy liquid coatings
Here is one place:
https://shopliquidrubber.com/products/polyurethane-deck-coating
Regarding the joists over the door (and the windows if you wanted): you can eliminate the wall headers altogether and use the rim board as the header if you use joist hangers on those joists and make sure the rim over the openings and 6in. beyond are continuous (basically, don’t put seams in or near the openings). FHB has covered this at least a couple times - first I remember is this great piece by Mike Guertin https://www.finehomebuilding.com/2016/07/26/headerless-wall-openings.
For your guard system above, you’ll want to figure out what that system is before you sheathe the top. Most manufactured systems have specific blocking requirements to fasten the posts to. I’d advise against trying a site-built guard system for this. The minimum 200-lbs resistance a typical 3-ft deck guard has to resist produces more than 900-lbs of force at the bottom of the post where it connects to framing. With a 4-ft post, that lever force is well in excess of 1000 lbs. The manufactured systems have to be tested to higher 500 or 600 lb (vs 200 lb) resistance, so are a safer route that is going to be easier to waterproof.
Oh that's a really good point on the leveraged force and additional reinforcement needed. Can you see any way to pull of a site-built one to keep the costs down, or do you have any manufactured ones you've seen which are at a lower price point with vertical bars or vertical cables? There's going to be about 50 feet of it so we're talking a few thousand dollars if going with some of the premade stuff I've found.
Interesting note on the headers.
Thanks
I don’t know about pricing for any of the manufactured systems. Some will design a solution for you based on your situation. It’s certainly within the realm of possibility to come up with a site-built solution, but I think you’re going to have a rough time waterproofing it if it penetrates the roof deck. It would be possible to mount the posts outboard of the rim (another Mike Guertin article covers details for that: https://www.finehomebuilding.com/project-guides/decks/rock-solid-guard-post-connections), but I think that’ll mess with what you’ve described for siding this structure.
This guide is super helpful - thanks. I'll probably put it on the outside to sacrifice aesthetic for the sake for easier waterproofing of the roof.
As a follow-up question, in this Simpson PDF (see bottom left diagram on page 3 of https://ssttoolbox.widen.net/view/pdf/xeuwdrqaen/T-C-GRDRLPST22.pdf?t.download=true&u=cjmyin) it shows two sets of straight line double blocking.
Do you happen to know how this is supposed to be attached to the joists? Is it done by toe nailing one side of the blocking, toe nailing both sides, hangers / connectors for the blocking, or some other method? I want to make sure I don't make a mistake that causes it to be weaker.
Thanks
The details are in the notes.
The ones with double blocking are to place the post inside the rim joist.
These are two cases, either supporting the post from a direction parallel to the joist, or at right angles to the joist.
Blocking to double the 2x8 graded joist needs 26 each 0.146 x 3 inch nails.
this is calculated to transfer the loads from the post. These nails would be nailed in straight (at right angles to the broad face of the 2x8s) and at 3 inches would just extend to the other 2x8.
In the parallel to the joist, all these go through the blocking into the joist.
In the right angle case, the doubled blocking spans two joist spacings, so the 26 nails get split between the two joist bays. (and attaches the doubled blocking to each other)
These nails would be spaced to spread the load.
The inset detail for the outside mounting of the post shows 3 nails at each connection of framing lumber, through the rim joist to the joist, and through the joist into the single blocking. You would select the nail details or alternate screws to meet or exceed code for the size of the framing.
the outside case does not need the doubled blocking because the location of the post can be selected so that the through bolt can come at the right position to secure the connector directly to the supporting joist (or blocking)
In the inside case, the post has to be placed so it is adjacent to the side of the framing member, so the double is needed to transfer the loads another inch and a half to the supporting framing.
The connector specified gets the length and type of connector specified (diameter and length) and the expectation is that every hole in the connector is used.
Remember,
Trees grow.
In width as well as height. Keep framing in mind.
Decking can be semi easily cut.