What type of screw and timber to start a tree house project?

[Jerry1]

Hi,

I am thinking to build a tree house with my kids. With absolutely no idea what to do, so I searched up YouTube trying to learn to build. Sadly, none of these tutorials taught me what tools and materials to buy.

The first step is to attach the timber on to the tree, like the picture below. But what kind of screws and what type of timber to buy? Can someone guide me through please?

There will be a lot of questions during the entire project but seems I am already stuck at the very beginning.

[EricL]

Hi @Jewelleryrescue

I understand your worry about the tree being damaged by the anchors applied to it. Trees are able to absorb a great amount of punishment from storms, hail and fire. The anchors being applied to it are mostly on the surface part of the tree and usually don't drive into the core. When a tree house is constructed the framing is often designed in such a way that it sits into the branches of the tree and the posts are there to provide additional support. Unless the tree is still very young putting anchors into it would damage it, but a mature tree would be able to manage.

Eric

[Jerry1]

@Noyade 

A great idea to fix a supporting beam.

My plan: A platform in 1M high, then another house in the upper level.

[EricL]

Hi @Jerry1

That's an excellent plan you've drawn up. I recommend putting in two supporting posts at the end so that you can turn one of them into the ladder assembly. In that manner, you'll get full support at the end of the platform. Since you're doing a second platform, the main platform has to be strong enough to hold an adult.

Eric

[Jerry1]

@EricL 

Thanks. What type of timber/screw shall I buy to fix the beams into tree?

[Dan_M]

I used treated pine self screwing M12 screws for mine

[EricL]

Hello @Jerry1

If you have a quick look at this discussion - Building a treehouse by @Dan_M, you'll see that he mentions a bolt called a TAB or a treehouse attachment bolt. The purpose of these bolts is to hold the framing assembly of the house without permanently fixing it to the tree. In that manner, the tree can keep moving and swaying without damaging the tree house. It also serves as a weight-bearing point for the assembly. Since the TAB is not available here you can use a similar bolt such as the M26 high tensile bolt that was used for Dan's assembly.  

However, since you're not building very high, it might be possible to anchor the treehouse frame to the body of the tree. You'll need to do some observations and see if the tree sways very much in high wind. One other method is to build the house frame with posts so that you don't have to anchor onto the tree at all.

If you need further assistance, please let us know.

Eric

[Jerry1]

Shall the screw go through the trunk or just nail in?

[EricL]

Hi @Jerry1

To prevent severely damaging the tree, I suggest only going halfway in with the length of the bolt you'll be using. If for example, you'll be using a 250mm bolt, you should at least have 125mm driven into the tree. The rest will be used by the timber framing of your tree house.

If you need further assistance, please let us know.

Eric

[dbaarda]

So I'm in the process of building a tree house after doing heaps of research and will eventually write my own topic covering it. But for now, the general rules of thumb about attaching things to trees are;

1. Trees don't like their bark being damaged, because it cuts their circulation above the damage, and creates an ingress point for moisture/mold/disease. So it's better to have fewer but bigger attachments than lots of little ones. Going directly through a trunk is not actually that bad and is about the same as having two non-through holes, but is usually unnecessary unless you want to attach things on both sides of the trunk. Its also a good idea to seal any holes with something like bees-wax. I put a food safe bees-wax based wood polish and raw bees wax (both from Bunnings) liberally on the threads of my attachment bolts to both lubricate (screwing in large threads to trees is HARD) and seal around the edges of the hole. 

2. Tree trunks grow wider as the tree grows, they don't grow upwards. This means you need to give clearance for the tree to grow, and avoid attaching things directly to or encircling the trunk. They recommend leaving about 5cm clearance around the trunk. Because they don't grow upwards you don't have to worry about things growing out-of-level.

3. Trees move quite a bit in the wind.  This movement is not necessarily that large, but it has enough force to shatter anything you attach to more than one trunk if you don't design it to allow for this movement. In general you can only have one "static" attachment trunk, and attachments to any other trunks need to be "dynamic" and allow movement.

The Nelson's Treehouse youtube videos and websites show their special Treehouse Attachment Bolts (TAB) and static and dynamic uplift arrestors for attaching to them with/without allowing movement. Unfortunately that gear is crazy expensive to buy from the states, and is probably overkill for most treehouses (those guys build tree-mansions with that gear). I made my own based on a bunch of online research using mostly stuff you can buy at Bunnings, with a handful of special bits from other online sources. I have photos and online OnShape CAD designs and will post a thread detailing them soon.

[EricL]

Hi @dbaarda 

Thank you for sharing your list, those are all excellent points you made in your tree house building rules list. It's definitely worth keeping in mind that a tree is a growing organism and its best to provide allowance for it when it expands.

We look forward to seeing your tree house project begin.

Eric