Posted on February 2, 2010 with No Comments
Most people, when building tree houses, never consider winter construction because they want to be inside when it’s cold outside. But there are a few good reasons to build during the winter. Building tree houses during winter may reduce construction induced stress on the host trees. Here’s 3 reasons why:
Building tree houses in winter is good for the trees and fun for us too!
1. If you need to wound a tree for building a tree house or general pruning, the dormant winter season is the best time of year to do it. The scent from tree wounds can attract insects that spread oak wilt or Dutch elm disease. We’re also concerned here in Pennsylvania about the spread of the Emerald Ash Borer. But insect and fungal activity is at a minimum during the winter so the transmission risk is very low.
2. Building in winter, just previous to the growth season, will also permit the tree to direct its spring vigor toward responding to the attachment point injury and the weight and wind sail forces from the new tree house. The tree will grow reactive tissue around the attachment points which helps the tree compartmentalize or “wall off” the wound. This extra growth, over time, is beneficial for the strength of the tree house and resists spread of decay in the tree. Trees also grow more and thicker structural roots on an as needed basis, so they will grow more roots to respond to the added wind sail effect created by tree house walls and the overall weight of the structure. These factors immediately shock the tree, but it will likely regain balance over a couple growing seasons. A tree house built at the end of winter, just previous to the onset of the spring growing season, will have the full benefit of that year’s reactive growth to help the tree adjust to the new wounds and loading.
3. Soil disturbance, one of the most serious tree threats during tree house construction, is much reduced during winter when the ground is frozen. Foot prints and vehicle tires can seriously reduce the ongoing health & vigor of trees when they compact the soil. Trees need air spaces between soil particles to aid in absorbing nutrients. But frozen soil becomes rigid, protecting those tiny air spaces from compaction.
Winter can be a great time for building tree houses. It may not be when most humans would think of tackling an outdoor project, but when we consider the arboreal benefits, perhaps more of us will wear an extra layer and build our tree houses over the dormant winter season.
Posted on September 27, 2009 with No Comments
Question From Peter:
“I’m thinking of using 4-5 trees as supports for a 12′ yurt platform. The platform would be only 1-2 feet up from the ground and placed on 2 (very) roughly parallel beams attached to 4 trees (each between 2 trees), with possibly a diagonal beam additionally attached to one of those trees and extending to a fifth tree (for center support).
trees, measurements, and treehouse platform layout
The distance between edge of platform and bark of tree would range from about 6 inches to 5 ft. (if there’s a center beam) or 3 ft. (if there’s not). I’m attaching a site diagram, for your reference. I believe the trees I would be using are pines. Their trunks are between 1 and 1.5 feet in diameter at 1 ft. above the ground, and they are very tall. It looks like their foliage is in the top third.
My questions are these: (3)
1. Would there be movement to worry about that close to the ground? If so, should I use fewer trees and partially support the platform from the ground?
2. Should I support the platform from the ground, regardless of how many trees I use?
3. While I am aware of hardware options, my preference is to use slings and/or lashings to attach the beams to the trees, with a layer underneath the straps to protect the bark. I would take down the yurt and platform on a yearly basis in order to adjust the straps, but otherwise, they would stay up year-round. When I’m gone from the site, I would remove the beams from the trees. Would this work? I’m aware there have been efforts to build treehouses without hardware, but can’t seem to find info about this on the web.”
Thanks for the questions, Peter, and I’ll tell you what I think.
1. If I were you, I would place several buckets upside down around a sample tree in the stand where you will build the treehouse yurts. Then place small boards on top of the buckets so that they run tangentially to the tree around it and are only about a half inch from the bark. Then go out there on a windy day and watch/measure how much the trees move at 1 foot high. They will certainly move, but I don’t believe they will move enough to affect your decision of what type of treehouse attachment to use. The principal is that the lower to the ground you are, the less the trees will move. However, what little movement they make becomes more difficult to stop due to leverage. Even if you theoretically could stop that movement, you might not want to because it will interfere with reactive root growth which strengthens the tree. Typically, I would use a floating bracket for attaching the treehouse to traditional fasteners like garnier limbs, but this is leading into your other questions.
2. If tree friendly construction is your primary goal, then you should consider using 100% ground support instead of attaching to the trees or using removable slings. The holes will damage some small roots, but with careful digging, this damage will be far less than penetrating fasteners. Either way, don’t forget that foot traffic around the treehouse during and after construction is often a much greater threat than using penetrating fasteners. I’ll also mention that you are diverting rainwater that would otherwise fall under the treehouse yurts and affecting where needles will build up over the years, but these issues are not as important as the above.
3. Some Japanese treehouse builders in the late 1990s did not want to penetrate the bark with fasteners, so they used large clamps. I understand that this practice has been found to do less short term damage, but more long term damage to the trees. Plus, it’s hard to get the clamps tight enough not to slide down the tree under the dead load alone… If you are committed enough to sling and resling the trees every year, then it might work out for you that way. Several arboretums in the Philadelphia area have held treehouse building events in the past few years and all of them had rules about not penetrating the trees. In my opinion, some of the non-penetrating methods were more damaging to trees than our normal practice of penetrating. If you go this route, please spend the extra money to get larger, wider, tree saving slings. These will have a greater bearing surface on the bark and will be less likely to cause grooves under the sling. They will also have higher load ratings so they will last longer when left out in the rain & UV. The primary concern, in my mind is that you are making regular work for yourself this way that may not get done enough, or that the slings may do surface damage to the bark a little bit at a time, especially while being taken down and reset, regardless of how careful you are about it.
Please leave a comment here after you consider all of your research and decide what to do. We’d also like to see a picture of your finished treehouse yurts! Thanks, and happy treehouse building, -Dan Wright
Posted on June 1, 2009 with No Comments
Top 10 Tree House Building Mistakes
1. Choosing a tree without consulting an expert
Building a tree house starts with a foundation analysis. What species is the tree? Where is the tree in its natural life cycle? Is the tree healthy - free of defects, decay, disease? You may not need a professional tree house builder or arborist to look at the tree if you know the basics or research your tree online. But first consider the level of investment you are making in the tree house before bypassing this step to save a few hundred bucks. How much time and money will you spend on the tree house? What is the intrinsic value of your tree? Every ground house starts with the footer inspection and then concrete, and every tree house starts with the tree’s structural grounding, core integrity, and health.
2. Neglecting to have even a reasonably basic tree house plan
It can be fun to build your tree house one board at a time. It certainly gets you started sooner. But this causes a few common mistakes. When there are multiple branches or trunks, your eye-balling methods may deceive you. You may find that in order to pass a main tree house beam where you thought you could, you have to cut a major branch (bad idea). Secondly, most people have trouble sighting level, especially when the grade is sloped. Note that a tree house platform constructed perfectly level will not necessarily be parallel with the ground. This matters because you may find that what you thought was a 10-11′ span may actually be 13′, which would require a stiffer beam and more support. So it’s back to the lumber store to return the 12′ joists and get some 16’s, and now you need 2×10s instead of 2×8s, increasing the weight, cost, and difficulty of the tree house unexpectedly. Even if you can sight level and your beams and spans work out, you may still end up trying to improvise extra tree house attachment points on the fly, which may lead to less than optimal decisions for the tree house and/or the tree. Our advice: climb the tree, take measurements, temporarily mark each beam, draw the tree house platform on paper, and do whatever else it takes to reduce the surprises once you start building.
3. Using too small or the wrong fasteners
Don’t assume that the biggest lag bolt on the shelf at your local big box home improvement retailer is suitable for holding up your tree house. Even a kids tree house with walls, windows, and a roof, will probably use a couple thousand pounds of materials. And then you need to allow for the tree house to also support live loads to cover as many people as can fit up there. It always pays to use the right fastener. Use screws or carraige bolts for places where the tree house will primarily be subject to pullout or tension forces. Use nails where shear forces are primary. Be careful to use approved fasteners for treated lumber. Beware that most of these mistakes will not cause tree house failure in the short term, so you might not necessarily know you made a mistake right away.
4. Using too many fasteners
Never place tree house fasteners too close together in the tree. Remember that trees don’t heal, they seal, or compartmentalize around each wound. If wounds are too close together, the tree may treat them as one wound, which will cause the wood between the fasteners to decay. This will almost certainly cause the tree house to fail. A better approach: Use one, large tree house fastener, instead of multiple smaller ones. I know it’s tempting to use the smaller ones because that’s what you can buy on the shelf, but don’t be lazy with tree house safety.
5. Pinning a beam to a tree
When a tree house beam is pinned to the tree, one of two bad things WILL happen: 1) the beam will restrict growth on that side of the tree, causing it to suffer, or 2) the tree will continue to grow, pushing the beam outward and right off the bolts it was secured with! Eventually, it will fall off and the tree house will fall down. It is advisable to “perch” the beam on a super strong professional tree house fastener like an artificial limb, rather than pinning a beam to the tree.
6. Inadequate stabilization of the platform
The tree house platform should be stable because any movement will wear parts loose over time and become more dangerous. We usually see problems with knee braces not being installed tightly to reduce movement. If the tree house fasteners themselves are moving, you have a big problem because the tree will never seal that wound properly. You will likely see liquid coming from the spot, the wound will remain open, the tree will suffer, and the fastener will get looser and looser and probably fall out.
7. Girdling the tree with rope, cable, or 2×4s
Don’t wrap anything around the tree to support the tree house. You can completely kill the limb or trunk if you do. Even if the tree survives, it will certainly suffer. We see this a lot on zip lines, and when cables or chains are used for tree house supports. We have also seen many people nail short 2×4s into the trunk to space the chains or cables 1.5″ away from the branch or trunk. That will lessen girdling, but it breaks rules #4 and #5. Get the right tree house fasteners to keep your tree happy.
8. Not leaving room for the tree to grow - boxing around
The tree house should only touch the tree where necessary. This means when you frame your beams, joists, rafters, etc., that they all need to allow the tree sufficient room to grow over time and sway in the breeze without rubbing the tree house. If you don’t do this, you risk girdling the tree and reducing the life of your tree house. If you later decide to extend the life of the tree house, your maintenance will be harder, so plan for growth. Ask an expert how fast your tree will grow.
9. Nailing ladder rungs onto the tree trunk
You may have seen a picture of 2×4 ladder rungs each nailed into a tree for tree house access. That is not nice to the tree. As a general rule, no part of the tree house should touch the tree unless it has too. There are many other ways to build a ladder or access the tree house. These types of ladders are repeat offenders for breaking rule #4.
10. Not bothering to preserve natural wood surfaces
Wood, whether pressure treated, cedar, or even bald-cypress has a clock. The sun, rain and snow will cause them to decay and the tree house will look older faster, and need replacement sooner. Commercially produced lumber does not last as long as the old growth forests. Profit drives companies to grow timbers faster, so they don’t build their natural resistance to decay and pests. If your tree house is built with reclaimed lumber, this might not apply, however, treatment will extend the life and beauty of any wood. At a minimum, protect your tree house by applying a clear sealant on the exterior floors, stairs, and railings every 1-3 years.
Questions? Contact Tree Top Builders for more information on safely building tree houses.
