Treehouse roof - sealing to tree?

[maverick302]

I'm partway through a treehouse build and will be getting started on the roof soon. Just to set expectations I'm a complete rookie at new construction. The plan is PT plywood sheathing, felt, asphalt shingles, and drip edging. The tree runs through the center of the structure and therefore there will be a ~24" hole in the middle of the ridge. Ideally I would like to seal it up to prevent water getting into the interior as well us under the shingles. I'm hoping there is an appropriate sealant or flashing that would work, and still allow for tree growth. Any suggestions?

 

[cgrutt]

My nephew built one believe he used a truck inner tube to seal off center. His was amazing complete with loft, wood burning stove and stained glass windows. Good luck.

 

[jack stand]

It's going to damage the tree and eventually leak anyway.
I'd just leave a good inch clearance and maybe stuff a pool "noodle" or similar into the void.
Sounds neat, pictures are always welcome.

 

[nateo]

It's going to damage the tree and eventually leak anyway.
I'd just leave a good inch clearance and maybe stuff a pool "noodle" or similar into the void.
Sounds neat, pictures are always welcome.

That was my first thought too. Jam something soft and replaceable into the gap and have a plan to deal with any water that comes down the trunk.

And also post pics.

 

[JeepYJ]

How do you have floor finished around the trunk?

 

[maverick302]

How do you have floor finished around the trunk?

Floor is PT ply, currently just a clearance hole cut around the trunk. We'll likely put in outdoor carpet or something as a flooring material. I was considering foam to fill the gap, since it doesn't really need to be watertight. Depending on the roof solution it probably shouldn't be watertight...

 

[maverick302]

It's going to damage the tree and eventually leak anyway.
I'd just leave a good inch clearance and maybe stuff a pool "noodle" or similar into the void.
Sounds neat, pictures are always welcome.

Pool noodle isn't a bad idea, and would probably take care of 95% of the water problem.

I used TABs (treehouse attachment bolts) as they are supposed to minimize damage to the tree. I'm trying to avoid as much physical damage as possible to keep the tree healthy

 

[CraigStu]

I think the important thing is sealing the edge of the hole in the roof to preserve your shingles and the plywood. Maybe strips of aluminum flashing 2"x6" bent in half at the opening edge and glued down to the shingles. A bunch of them overlapping each other 1/2" all the way around? Also from my experience on a play house on stilts, do the full standard drip edging etc. I had figured ah, just let the shingles hang over an inch will be OK. 20 years later I had to trim the roof edge back 3 inches to get rid of the rotted plywood and figure a way to do the drip edge after the fact. Sure glad I built it w/ 8inch overhangs. BTW, for the floor I used standard PT deck boards w/ 1/2" gap so whatever rain got in had a way to get out.

 

[mike93lx]

I used Pete Nelson's hardware for my treehouse too. Good stuff.

I bet if you put a diverter uphill of the tree, you'll have little to no water coming in. A pool noodle will then stop the rest of it

 

[Augus7us]

I thought Pete used large hemp rope for sealing around the tree? I imagine a pool noodle will work just as good.

 

[firebirdparts]

I did one, fairly elaborate, on standoffs with no connection to the ground. My suggestion is don't even try unless you're planning lots and lots of interior finishes, carpet, upholstery. The rain really won't come down through that hole. Just a little bit. In the summer it'll be zero. Configure it so that the water coming in with the tree goes out with the tree through the floor.

Plugging it up temporarily could work, but you'd still need to remove it as the tree grows. Diverters could work if you don't ring the tree all the way around.

the structure doesn't really last all that long as the tree will blow it apart in about 10 years. if you try to avoid mold, then sure, that's worth doing.

The one I did, the tree seemed to grow extra fast after I built it. It's amazing how they do fill that hole.

 

[66Caprice]

Build interior walls around the tree stump with several inches of clearance then put windows all around the inside. then you can watch the tree grow and the water flow and never have a leak...

 

[bwringer]

... Configure it so that the water coming in with the tree goes out with the tree through the floor. ...

This. And leave more room for growth than you might expect to need.

 

[imagineer]

Some time in the late 70's, I saw where a through-roof style treehouse was weather proofed by using a thatched roof type design. The guy who built it placed the 1st course of reeds at a steep angle spanning close to the roof opening and resting on the tree trunk. He used sisal twine to hold the reeds to the tree. The rest of the layers were woven to the first course. Basically, the 1st few courses were backwards, but the outer ones were laid in the correct orientation.

I recall he and his kids saying that if it rained heavy, a small amount of water ran along the tree bark, but it didn't rain inside the treehouse.

 

[Voi]

I thought Pete used large hemp rope for sealing around the tree? I imagine a pool noodle will work just as good.

This is what I remember from one episode of his show. One of our GJ members had Pete build him a tree house. I'll see if I can remember his username. I don't recall if his has a tree running through it.

 

[Voi]

This is what I remember from one episode of his show. One of our GJ members had Pete build him a tree house. I'll see if I can remember his username. I don't recall if his has a tree running through it.

I believe the member was @FTWingRiders

Worth look through his profile to see his thread.

 

[FTWingRiders]

Our treehouse that Pete built didn’t have a hole, it spans between 4 equal good sized Oak trees.

https://www.garagejournal.com/forum/threads/anybody-catch-treehouse-masters-tonight.380063/

How weathertight/climate controlled do you plan it to be? Two thoughts, plan the hole larger than you think, as we’re surprised how much ours have grown in the couple years it’s been. My guess nobody really pays that much attention tree growth rate, but depending on its species it could be an issue.
Also take into account sway, there’s going to days that the treehouse and the tree could be affected by strong winds.
I’d assume you’ll always have some water run down the trunk and plan for it to continue past the floor.

 

[maverick302]

Our treehouse that Pete built didn’t have a hole, it spans between 4 equal good sized Oak trees.

https://www.garagejournal.com/forum/threads/anybody-catch-treehouse-masters-tonight.380063/

How weathertight/climate controlled do you plan it to be? Two thoughts, plan the hole larger than you think, as we’re surprised how much ours have grown in the couple years it’s been. My guess nobody really pays that much attention tree growth rate, but depending on its species it could be an issue.
Also take into account sway, there’s going to days that the treehouse and the tree could be affected by strong winds.
I’d assume you’ll always have some water run down the trunk and plan for it to continue past the floor.

That is awesome! I'll definitely look for your thread on that.

We won't be climate controlling. 100% waterproof inside isn't really the goal, just enough to avoid recurring wetting and the resultant mold/mildew/rot. Like @CraigStu said, water getting under the shingles can ruin even PT plywood in a hurry, so that's where I want to get it right.

 

[tarmy]

I don’t have any great pics of it. But this one had a tree that was in the middle like your plan. I left about 3 or 4” gap around the trunk with the framing for room for the tree to grow. I basically ran the asphalt shingles long over that gap which I had filled with expanding foam from a can. Then I “sealed” the gap by gooping Henry’s roofing tar around the tree and over the shingles. Worked great for about 10 years. I think I may have redone the tar once in those years. The kids and treehouse are long gone but the tree is still growing.

 

[ZRX61]

It's not necessary. Trees shed water out & away from the middle so the rain ends up falling from the leaves onto the outer limits of the roots away from the main trunk.
No one will want to be in the treehouse when it's raining anyway for the same reason you shouldn't shelter under a tree during a storm.