Need Tree Platform Build Advice

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  #1  
Old 05-21-17, 04:13 PM
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Lightbulb Need Tree Platform Build Advice

Hello All,

First time here and I am hoping someone can help me with my issue.
I have been planning platforms for the past couple weeks for the kids and am starting with the most basic one.

Rough sketch is attached below..not exactly to scale.

I know the basics and have some prior training building.
I am NOT a math head and that is my weakness.

Dimensions are 8' x 16', see diagrams for more specifics.
Roughly about 6' off the ground.
Two trees with 1' diameter.

I have two different designs for this making a platform, the main concern is the 8' span between trees.
I need it to support an active weight of say 500lb around the middle.
2 Adult + 2 kids

I know traditional route is 2 beams parallel to the trees, however I am concerned the one tree is leaning a bit.
I might not be able to make it a straight line, it may be over 5 degrees, perhaps 10.

In the first design I have 2 beams 2x8x16
Joists are 2x6x8

Hense build number 2 going with 4 horizontal beams and following up with 16' joists.
The main question dogging me, will plan number 2 be SAFE and FEASIBLE.

4 beams are 2x8x8
Joists are 2x6x16


Please see attachments.

Specifications:

Douglas Fir #2 Kiln Dried for all structure.
Beams 2x8's
Joists 2x6's
Plan on spacing joists 16" apart.
Traditional V support on each tree.
3/4 8" Hot Dipped Galv Lag Screws
3/4 10" HDG Lags for the V's
galvanized joist hangers
galvanized rafter ties

Was planning on using 1 x 6 x 8 boards for the deck across.
Not sure what wood to use, this is the most expensive part.
Options I have been thinking about.

T1-11 Plywood or OSB floorboard.
Whitewood Common / 1" doug fir boards, treated with wood sealer / preservatives.

Redwood / cypress is out of my price range, wife is allergic to cedar.
I am open to ANY and all suggestions.

Trying to keep this under 300-400.
I do not have the budget for expensive things like TABS,
I am trying to preserve the tree as best I can with single lags.

Thank you for your time.
 
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Old 05-21-17, 04:35 PM
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Welcome to the forums!
1) How will you support this without killing the tree(s)? Lag bolts will kill them.
2) Lateral stability will be a problem
3) What will you do when the trees grow in length and circumference at different rates?
4) Looks as if you have precluded all woods besides pressure treated pine.
5) You'll need Simpson Strontie fastening methods for the joists to the beams
 
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Old 05-21-17, 04:46 PM
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Hello Sir,

Thank you very much for your reply, although I am a little confused.
I am told by many professionals to use LAG since I can't use TABS.
If lags would kill them the larger TABS certainly would...

Lateral would be braced with 2-4 V's near the base of each tree.
I am unable to use posts as that would cause it to be considered a deck and subject to all sorts of regulations I do not have the funds for.

These trees have not hardly grown at all since we have lived here.
Circum of the first tree is 48" and it was little under 47 three years ago.
I have round holes in the floor cut approx 2.5" far from the tree, could go 3.

I am not using PT Pine, it is doug fir kiln dried, also in the PT version.
I am told doug fir has very good stability even PT form, better than pine.

So would the version 2 of the plan work or not?

Thank you for your time.
 
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Old 05-21-17, 05:06 PM
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I am not an advocate of driving 3/4" c 8" lags through a tree in two places, plus whatever you use to stabilize the angle braces. I am not a tree hugger, just not wanting to kill trees unnecessarily, which it will do.

With that said, if you have douglas fir available, then, by all means use it. We don't have that luxury in the south. The holes in the flooring won't matter since your framing will be up against the tree (as pictured in your drawings), making any growth a peril to the construction.

You can't cantilever more than 2', but it's not a deck. If you have the blessings of the authorities, then your methods will work.
 
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Old 05-21-17, 05:14 PM
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Hello Sir,

I am too worried about the lags as I certainly do not wish to kill the trees.
Would 1/2 do since we are not dealing with much weight.

I was also suggested to use the A suspension method for the deck which I am considering...but that still puts bolts in the trees...

My understanding if the lags were level that would cause the tree to treat it as a single wound and would not lead to dangerous compartmentalization.

Would you not put the lags across from each other?
Should I just put the 2x8 together 2ply and use one single 10" lag?

I certainly want to know the right way to use lags, please teach me.
Since this is for my kids I certainly want to do it the right way.

just to clarify in live in the NW and we hardly get any wind here,.
I also have 2" lateral slits to accommodate movement and circles cut to accommodate for tree growth.

Thank you for your time.
 
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Old 05-21-17, 05:51 PM
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Just to clarify I am trying to built this similar to what this person did.

However is they are obviously an idiot for doing it this way then please just come right out and say so and save me time, effort, and money.

How to Build a Treehouse: 16 Steps (with Pictures)

Also

http://www.wikihow.com/Build-a-Treehouse

Thank you.
 
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Old 09-20-17, 10:15 AM
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One problem with this build is that most lag bolts/screws are ungraded so you don't have any clear idea as to how strong they really are. My understanding is that the sort of steel that comes from China that ends up in many of these bolts is really inconsistent with regards to quality.

A better option (in my view at least) is to cook up your own tree attachment bolts. If you contact industrial fastener suppliers directly, you can actually get pretty good prices on them. For my build, I called****************directly. They will sell to individuals if you buy a minimum of $25 worth of stuff. I got some Grade 8 Zinc plated 1.25" x 12" threaded bolts for like $13.00 each. Shear weight for that bolt is tested at 80,000lbs. Then I stuck those 7-8" into the tree with a couple heavy duty washers and mounted my support beams on top of them. (put flat steel on the bottom of the beam) Then I used a closed bar holder to create a slot that permitted sliding, but not lifting. (like a TAB)

It's not quite the same as a TAB, but it's a hell of a lot better than pinning the beams to the tree.
 

Last edited by Shadeladie; 09-20-17 at 11:19 AM. Reason: Link to company removed
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