'Good is...?' - Tree house - Building

Before building a tree house, it's best to go through these simple seven stages:

1. Check the planning/building regulations in your area
2. Design the treehouse plan before you start cutting any wood
3. Keep supports separate to the house framework
4. Allow flexibility in the supports if you use more than one tree
5. Use single large bolts for attachments to the tree
6. Avoid restricting tree growth
7. Build as much as possible on the ground

1. Check the planning/building regulations in your area

• In urban areas planning regulations can easily demand that your treehouse is removed on safety, distraction or regulatory infringement grounds.
• Every area is different, but some general guidelines apply.
• Ask officially before you build.
• Speak to your neighbours before you start. If anyone objects it is most likely to be them. Discussing your idea will make it much easier to get their approval.

2. Design the treehouse plan before you start cutting any wood

• Map the supporting trunks or branches at your proposed floor level. Use string to mark the height on each trunk and draw the layout on squared paper.
• Work out the best support method.
• Lay out the floor.
• Draw the house to fit on the floor. The free Google Sketchup software works well.
• Involve the client. If the treehouse is for your children, ask them what features they would like and let them help with drawing up the plans. Make sure they feel that it is their own treehouse.

3. Keep supports separate to the house framework

• Aim for a level floor capable of taking the entire weight of the house. It is much easier to build a rigid house on a solid, flat floor than to rely on other parts of the tree for support.
• Avoid fixing any walls or parts of the roof to branches passing through.
• Walls need to be rigid enough to support their own weight plus the roof.

4. Allow flexibility in the supports if you use more than one tree

• If more than one tree is used they must be allowed to move in the wind or the treehouse can be easily damaged.
• Use either metal brackets or cables to allow flexibility.
• Building between two trees is the easiest system for large treehouses. More trees means allowing movement in different directions, which is hard to absorb.
• A popular flexible design uses a rigid floor unit that can slide over the beams below, allowing the beams and the trees to move.
• To reduce excessive movement, bolt one part of the supports to the largest tree of the set, allowing the other end(s) of the support(s) to move flexibly.

5. Use single large bolts for attachments to the tree

• Single puncture wounds at each attachment point cause much less tree damage.
• Large bolts are much stronger than screws or nails.
• Lag bolts are preferable to through bolts as less damage is caused.
• Check fastening ratings and always overbuild each joint to take at least three times the projected weight of materials and occupants

6. Avoid restricting tree growth

• Don't tie straps or ropes around the tree as this will strangle it over time.
• Add spacers between beams and the tree to allow room for growth during the lifespan of the treehouse, or use very large bolts which have plenty of the shaft exposed and mount items on the end.
• Allow a 2" gap around the tree if it passes through the floor
• Add at least a 3" gap around the tree if it passes through the roof (more if the tree flexes much in the wind)

7. Build as much as possible on the ground

• Design the treehouse in separately built sections that can easily be joined together - supports, floor, walls and roof. These can then be pulleyed into the tree and quickly secured in position.
• Using power tools is easier.
• Building on the ground is safer.
• Parts will be prepared faster and more accurately than if constructed in the tree.
• In remote locations prepare a proper work area before you start.

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Finding the perfect place to build - Picking your tree

Height

The higher you go in a tree the greater the sense of freedom and the more amazing the views you get will be. However, you must also think practically - in terms of safety in the case of a fall, wind speed and quality of support. Children's treehouses are usually more suited near the ground up to 3 metres (10 feet) to minimises the danger from a fall.

Trees can move a lot in the wind and adding a treehouse, which is essentially a sail, will only help to increase the wind catchment area. In particular, this effect will be greater in a storm. Usually trees can deal with excessive wind speed by losing parts of their structure in the order of leaves, small branches and large branches. As each of these is lost, the wind catchment area of a tree decreases, helping to reduce the pressure which may lead to the entire tree blowing over. A properly constructed treehouse may not disintegrate until wind speeds are great, so all the pressure acting on it is helping your tree get pushed over. Treehouses in high wind areas should be in the lower third of the tree, where wind speeds are lower and the leverage of the force on the tree is reduced. If the wind poses a serious danger, keep size to a minimum and try to build a more curving, or circular, house to reduce the sail effect.

Branch thickness

The points where you fix supports will need to be strong enough to hold the weight of the part of the house they are supporting. It is simpler building with a few long supports than lots of smaller ones. This will require several attachment points (four is good) across different trees. Although branch strength varies between species of trees, these are some guidelines. Excellent trees are oak, beech, maple, fir and hemlock. For a one storey treehouse with no overhanging parts a minimum thickness for four attachment points (one at each corner) is about eight inches. If you have more than one storey and/or the extra leverage and weight of overhanging sections, then you may need twelve inches or more. If your branches don't allow for this, use more attachment points so the weight is spread out better.

Building between different trees or trunks

If you are planning to use two or more branches, trunks or trees, you must be careful when fitting supports. When there is strong wind, a tree will twist and sway quite a lot. You must not seriously restrict this movement because it could destroy your house. This mostly occurs when building across two very long branches because they catch the wind easily and can swing around a lot. Different trees and different branches will move differently, so the supports must be able to cope with any tension or compression. The options are having a strong rigid framework or a weaker flexible framework.

Tree damage

Before you start work on your treehouse, read through the tree damage page for the common treehouse related injuries and how to avoid them.

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Legal aspects of building a tree house

Legal planning

An unwelcome and sometimes intrusive service, the legal system of planning regulations and building codes can cause many a head and heartache for would-be treehouse builders. The myriad laws governing building work are generally designed to provide a uniform and measurable level of safety for occupiers and have, of course, done well to protect people from serious structural failings and health hazards in regular buildings.

You will either agree or disagree with how I view treehouses and the law. My impression of a treehouse is that it is a fun exercise - something that takes hard work to build but which will give you a huge sense of achievement and a lasting, useful addition to your garden. Involving children in various parts of the work teaches them many practical skills and gets them occupied with something creative, rather than television or video games. One of the reasons I started this web site was because I think treehouses are so great that everyone should have the chance to build one. In my communications with other treehouse builders the law has, in every case I can think of, been a hindrance to the builder. In the pursuit of ever more restrictive safety regulations, the inherently unconformist features of a treehouse are widely frowned upon and condemned by officials.

Keeping on the right side of the law

• Build on your own land, or at least have permission.
• Discreetly ask around the neighbourhood for people's general thoughts on your treehouse.
• Very discreetly ask around the local council/governing body to determine if any laws exist regarding treehouses. Not many areas have specific laws, but if so, study them in detail.
• Keep away from boundaries. These are definite no go areas for building and should always be avoided. No part of the structure should reach within ten feet of the boundary of your property, although this distance can vary.
• Design the house to avoid having obvious privacy-infringing areas, such as large windows or balconies overlooking neighbours or roads.
• Try to choose a site that's not visible from the road. Not everyone who sees your treehouse will be impressed and anyone can make a complaint.
• Don't consider making an official planning application unless you are properly prepared. Getting a building permit is hard going for a treehouse. You will need a structural engineer who is prepared to validate the strength of the design, which is not easy. Treehouses are much more dynamic in their support and movement and so are difficult to quantify into real stress and strain measurements.
• Keeping the size and design a little restricted demonstrates that the treehouse is a 'temporary structure' - the magic words. Convincing the authorities of this label is important to help negate the need for a building permit. Remember, sheds don't need permits so be prepared to describe the treehouse as such. Temporary structures usually have height restrictions (eg, fifteen feet in some places) which you are quite likely to breach building in a tree - unfortunately there's little you can do about that, other than hiding the offending parts.
• Avoid fitted electricity and plumbing. You will be giving the impression that the building is to be used as accommodation, and that is simply not the route down which you want to travel. Your treehouse must not appear to be a potential dwelling. Many, many restrictions will apply if it does appear to be occupied or if the intent is there. You can always run an extension lead for electricity up there as another 'temporary' measure.