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A lean-to is a classic shelter of the northern forests. It is an open-fronted shelter that depends upon fire to keep the occupant warm.

This type of shelter has the advantage of a relatively simple construction method requiring few tools.

As long as you have access to plenty of firewood, a lean-to will keep you protected from the cold in otherwise lethal temperatures.

There are, however, a few tricks to getting it right first time.

The Value Of A Lean-To In The Northern Forest

All the photos in this article were taken in northern Sweden, well inside the Arctic Circle. I slept out in the shelter depicted in night-time temperatures that hovered between minus 20 and minus 30 degrees Celsius. This is colder than inside a domestic freezer. I did so without the aid of any sleeping equipment – no sleeping bag, bivvy bag, blanket or the like. Moreover, I was not at all concerned about freezing to death and I did get a reasonable amount of sleep. This is the value of a lean-to.

Shelter Position And Orientation

Before you begin constructing your shelter, you should take some time to find a suitable location and determine the appropriate orientation.

Standard considerations for shelter-building apply with respect to positioning, orienting and building this type of shelter, with some of these considerations even more critical in a winter setting.

Make sure there are no hazards overhead, from dead trees or hung-up branches.

Think about the lay of the land – avoid localised low points where cold air will accumulate. This is particularly important in winter.

Find the most naturally sheltered spot – any breeze will diminish the effectiveness of your shelter. Think also about gaining some protection from natural screens of small trees and overhead branches of larger trees.

Standing out in the open on a clear night in arctic conditions, you can literally feel the heat escaping upwards from your body. Any overhead protection from live branches will be of benefit.

A key consideration in building any shelter is the local availability of construction materials. When you are working on snow, even on snow-shoes or skis, the effort required to gather materials is multiplied. Make sure there are plenty of materials near to your intended shelter site.

Given that a lean-to shelter requires a fire to keep you warm through the long winter nights, you will need a plentiful supply of firewood. The most efficient way of collecting firewood is in large pieces. Look for dead trees that are still standing. Moreover, if you want to get any sleep rather than tending the fire all night, your firewood must be substantial in size. It will burn with a steady heat for a reasonable period of time, allowing you to get your head down. I look for one or two dead-standing pine trees in the immediate vicinity of where I am going to build the shelter.

The orientation of an open-fronted shelter is critical. Ideally the shelter, fire and any breeze or wind are parallel. There is a common misconception that putting the back of the shelter to the wind is beneficial. While it is beneficial in terms of being a wind-break, there will also be an effect like water flowing down a rapid. That is, there will be an eddy which re-circulates in the opposite direction. If the back of the shelter is to the wind, the re-circulation of air – and smoke from the fire – is back into the shelter. This is very unpleasant for the occupant of the shelter. Better to put ends onto the shelter and have the breeze blowing across its open front.

Finally, if you can, orientate the shelter so that the open side of the shelter gets the sun during the day. Assuming you are living and working out of the shelter, this will help keep you warm during the day. If you can only get the sun for part of the day given the other constraints such as wind direction, getting the sun onto you and your shelter in the morning will make the most difference.

The Right Tools For The Job

You could build a lean-to with only a belt knife and a folding saw. It would, however, be very difficult to complete within a day. The more critical point, though, is that with only these tools you wouldn’t be able to access the size of firewood needed to make this shelter work for you.

An axe is the most important tool you can carry in the northern forest. In high latitudes the growing season is short. Consequently, trees grow slowly and their wood is dense and knotty. In winter, you always need to process a lot of firewood, even if you are staying in a heated tent or cabin with a stove. An open-fronted shelter such as a lean-to is very inefficient in its use of fuel. In one night you will burn as much firewood as you would in several days in a heated tent. An axe is the number one tool in this environment.

Make sure you are familiar with using your axe in mild conditions before heading out into the north woods in winter. Even then, still be extra careful. Using an axe while wearing gloves or mittens, on skis or snowshoes, with snow rather than solid ground under your feet, increases the risk of mishap.

You should also make sure you are efficient with your axe. To get the most out of your axe in winter, your skills with it should be well honed. Precision and the ease of long use only come with practice. Specifically for building this shelter you should be quick at harvesting and limbing small trees as well as cutting poles to length while holding the pole in one hand and the axe in the other. For firewood, you should be confident in safely felling, limbing and sectioning trees of over 12 inches (30cm) in diameter. These are the basic jobs of winter survival with an axe in the boreal forest.

While an axe is the essential tool, a saw will come in handy. Some jobs are quicker and more efficient with a saw. For example, when sectioning a tree trunk, a saw is less wasteful of materials and energy. It is also safer. A saw also makes felling trees safer too, as the back cut can be more finely controlled.

A snow shovel is a much under-rated tool of the north. A good one makes moving lots of snow relatively painless. A key feature is a long handle or, at least a handle that will extend to a good length. The aim is to be able to move powdery snow in a broad, sweeping motion from an upright standing position.

To build your shelter you will need to clear an area of snow, down to the ground underneath. If you have a snow shovel, make good use of it. Otherwise you will have to improvise (more on this below).

The Ability To Light A Fire

The open fronted lean-to arrangement is dependent upon fire to keep you warm. Therefore, you must be able to light a fire. Carrying with you several means of lighting a fire is a basic survival tactic. Here sparks and matches work well and are reliable. There are common natural materials such as birch bark and tree lichens that will readily take a spark or small flame. Small kindling abounds on the lower trunks of spruce trees.

How To Construct Your Shelter

Once you have chosen the site and orientation of your shelter, you will need to find a couple of sturdy trees with enough space between them to house your shelter. Then you can get down to the business of construction.

First you should clear an area sufficient to house a raised bed, fire and the area in between. While possible without a shovel, this is much easier with a shovel or similar implement. Snow in the northern forests typically remains powdery and can even transform to a sugar-like crystals, which are even harder to move in any great quantity without the appropriate tool.

If you don’t have a shovel, improvise something to scoop snow, preferably with a sweeping motion from a standing position. Provided you have an axe, you can rough out a long-handled snow scoop of a similar size to a canoe paddle but with a curved blade. The action of using this is similar to a canoe paddle too. Alternatively, you could use a snowshoe, improving its ability to hold snow with a covering of any spare cloth or plastic you might have with you.

Second, you need to locate and cut a sturdy cross beam for your shelter. This, like all the other structural parts of the shelter, should be made from green (i.e. live) wood. This cross beam is then lashed between the two trees you have chosen. In the northern forest in winter, it is not possible to improvise natural cordage. While there are abundant spruce, pine and birch roots below the ground, the earth is frozen solid. Carrying some cordage with you is also a basic survival strategy for this environment.

If you do not have any cordage, or do not have enough to spare, you can prop the crossbeam in place with sturdy Y-poles from the front of the shelter. In either case, the cross-beam should be placed between the leaning back wall of the shelter and the upright trees. This way the weight of the bulk of the shelter is forcing the cross-beam onto the uprights rather than trying to separate it from them.

The height the cross-beam should be lashed onto the trees is determined by the height and width of your bed and the desired angle of the back wall of the shelter. Generally an angle of around 60 degrees is good. If there is any chance of wet precipitation (e.g. sleet or rain) then 60 degrees is the absolute minimum angle. The bed should be wide enough for you to lay on it and high enough off the ground that you can sit on it at normal chair sitting height.

Once you have lashed on the cross-beam, add green poles at the desired angle. Collect the trees and bring them back to the area of the shelter to remove the branches. These will provide the thatching and bedding material for your shelter. If any of the poles are too long, you can trim them down, using the excess to form the basis of the platform for your raised bed.

Ideally, you will lay the poles right next to each other, with no gap in between them. This makes for an awful lot of work, as well as requiring the felling of up to one hundred live trees. Spacing the poles at around a hand span apart is a suitable compromise, particularly if you are not in a survival situation. This will prevent the thatching material from falling in between the poles but will not be quite as wind-proof as having the poles side-by-side.

To sleep out in this environment, you should be insulated from the ground, to minimise conductive heat loss. Air is a good insulator. If the underside of the sleeping platform is kept open to the fire, this will also allow radiant heat and the circulation of warm air under your bed.

The basic bed platform should be made of long poles that have a little give in them. In this environment spruce is best. They should all be of similar diameters. Any tapering can be compensated for by laying the poles head-to-toe. This is then covered with spruce boughs. While a thick mattress of boughs makes for greater comfort in its own right, it also insulates you from the warmth of the fire coming up from under the bed. So, you have to strike a balance between both these components of your comfort.

When thatching the back of the shelter, start at the bottom of the rear wall and thatch upwards, working right across the wall. You are aiming for the material to be 30-40cm thick at a minimum. Place the branches on with their stems facing upwards as much as possible, interweaving each new row with the last. Remember to also thatch the head and the foot of your raised bed to minimise draughts. An optional addition for extra wind-proofing is to add snow to the back of the shelter, over the top of the thatching material.

How To Construct Your Fire

There are various fires you can use with this type of shelter. All of them have one thing in common – they lie parallel to you and your bed. The length of the fire should be at least the same as your height so you are warmed from head to foot.

A classic, easily constructed long-log fire is made with three logs – two at the base and one on top. The thickest log you have goes on top. There is an old saying in the north that “wood as thick as a capercaillie will burn all night”. That’s a pretty big log!

The knack with this type of fire is to get the logs burning steadily and giving out heat like a grill.

You start by placing two logs on the ground and lighting a fire in the usual manner in between and making sure it spreads along the full length of the logs. Lots of small sticks and some intermediate sized fuel ensure this. Now, if you put a large log straight on top of this lot, it practically smothers the fire. This means lots of smoke and not much heat when what we really want is the opposite, little smoke and good heat.

The trick is to hammer some substantial pieces of green wood (about 2 inches/4cm in diameter) diagonally between the two logs to form an X-shape at each end. The large log is then cradled by these X-stays and held separate from the logs below. You obtain a constant flame which gives off a good heat from the gap in between. The stays take a good while to burn through as they are green.

Where To Place Your Fire

The common mistake with this fire is the put it too far away from the shelter. This misjudgement is often based on sitting on the raised bed and feeling the warmth on your legs. When you lie down you are then too far from the fire, particularly when it dies down a little.

The fire needs to be close enough to be able to warm the rear wall of the shelter, which will help keep you warm indirectly, adding to the direct radiant warmth of the fire hitting your body and the warmth coming up under your open-fronted raised bed. This all translates to the fire needing to be a short step away. You are left with just enough room to get your feet down in between the shelter and the fire while sitting on the bed.

Aim To Sleep But Adjust Your Expectations

You can of course sleep in this shelter using a sleeping bag or a blanket if you have one. Just be wary of sparks melting holes in synthetic shell materials. If you apply the principles above correctly then it is perfectly feasible to spend the night outside in arctic conditions in only the clothes you are wearing.

If you have a big overcoat, you can use this as a blanket. Personally I find I sleep best on my side with my front facing the fire. Therefore I tend to keep wearing the overcoat but have it open at the front – this means my back is kept covered and warm while my front gets the benefit of the fire.

There is a common myth that you will not wake up if you get too cold. I can assure you that as soon as the fire dies down a little and you start to feel the chill of the night, you will be awake. As the fire dies down, it also tends to produce more smoke which, if it comes your way, will also likely wake you up.

Once you are awake, the job is then to adjust the fire so that it regains the warmth required for you to fall back asleep. Make sure you have plenty of wood ready before dark. You’ll burn through more than you expect in a night and unless the logs you are using are huge, you’ll probably have to replace at least the top log during the night.

So, you will manage to sleep. It will just be in shorter stretches than you are used to. You will likely feel tired the next morning but you’ll be warm and alive. You will also have the inner glow that comes from surviving a night out in the open in the arctic forest with nothing other than your bushcraft skills and knowledge.