Introduction: How to Stack and Ventilate Firewood With Pallet Wrap

Just as pallets are incredibly useful, so too is 'pallet wrap' - a very thin, transparent and incredibly strong plastic film supplied on rolls which is both stretchy and self adhesive. Other than a pallet itself - surely there is no other product with such useful qualities? The number of possible uses is endless, but helping stack firewood must be somewhere near the top of the list.

Why do we need pallet wrap and why do we need to stack firewood at all?

First of all, firewood needs to be stored somewhere dry, preferably for about 2 years, so that most of the moisture within the wood is evaporated or else much of the precious carbon energy locked in the wood is wasted by evaporating large quantities of water in the fire itself. Check out 'The latent heat of evaporation of water'.

Secondly, stacking wood saves space and thirdly, pallet wrap stops our stack from collapsing and provides extra heat from the 'Greenhouse' effect of using translucent film.

We could just throw our precious logs onto the ground and cover them with a tarpaulin, but this has many problems:

  1. The logs in contact with the soil will stay damp
  2. It takes up a lot of space
  3. Tarpaulins are expensive
  4. There won't be much ventilation for the logs to dry effectively

I stack my logs on pallets to keep them off the ground and help with ventilation - some air can circulate under the log stack. I also create special vents in the pallet wrap to help evaporate the water..

But let's just go back in time a bit to last year when I wanted to stack my firewood on a pallet to dry. The middle of Summer is the best time to do this job as it gives the wood, which was cut the previous winter, enough time to dry for the forthcoming winters.

So, I was dutifully stacking my wood thinking what a nice pleasant and easy job it was and after getting to about 1 metre (3 feet) high ........ One of the corners of the stack spontaneously collapsed and I literally had to rebuild the whole thing from scratch - DOH!

Stacking wood is a lot easier against a wall or in a shed where you have upright surfaces to lean it against, but my stacks need to be free standing like in the photo above. Anyway, after rebuilding the structure 3 more times, I realised that I had to give the whole task a great deal more thought and consideration before the next build.

Step 1: How It Works

The log stack is ventilated by a combination of natural ambient wind and hot air convection currents induced by the 'Greenhouse Effect' within the stack.

When the sun is shining, convection currents occur as expanding hot air requires an escape route. If the sun is in the west, then the west facing sides of the stack get warm - up to 40 degrees C so far. The hot air expands and rises and this movement sets up a circular current inside the stack which results in air moving downwards on the colder East side of the stack and out of the vents.

The simulation above assumes that the wind and sunshine is coming from the same direction. The air comes in from the vents and under the pallet on the left hand side and rises up into the top of the stack by convection currents and comes down again and out of the vents again. The graphs at the 'Graphs' step confirm that air is moving fairly freely, even deep within the stack, by showing constant temperature and humidity changes on the probe located therein.

If the humidity in the centre of the stack was a constant 100% and the temperature never changed much, then the conclusion would be that there was no air circulation and inevitably our logs would turn to compost.

Step 2: Key Considerations

  1. Protection against the rain.
  2. Having enough ventilation to remove moisture in the wood.
  3. The stack does not fall down or fall on top of anybody.
  4. Easy to build without too much skill.

In theory, we could build the log stack without pallet wrap if we had the skill or were just plain lucky, but to make sure we are successful, pallet wrap is the answer. But why risk the stack falling over at all? What if a child was playing nearby or started to fiddle with some of the logs at the bottom or even climb up onto the top?

Other than using pallet wrap, I have also attempted to stack the logs with the best possible technique. Looking at the first photo above, the blue line shows the vertical and the red lines show where some of the corner logs are sloping downwards slightly - this is to stop them spontaneously 'popping' out of the wood stack and causing total disaster!

The photo shows the 'XY' plane, but we also need to have logs doing the same thing in the 'YZ' plane. If this is beginning to sound complicated, then looking at the computer simulated log stack in the video or next photo should help. Who would have thought that we'd need computer simulation to learn how to stack firewood?

A big problem with creating a stack of wood is that everybody, when asked, will reply 'yes' if they are asked: 'Do you know how to stack wood?'. What could possibly go wrong with something so simple?

If firewood was the shape of regular bricks, it would be much easier, but we'd still need interlocking corners.

Summary: Try and get the corner logs to interlock and slope downwards slightly into the stack in both the XY and YZ planes.

Step 3: The 'Magic Log'

The computer simulated log stack shows much more clearly how to actually stack firewood without the whole stack falling over. In purple, we have our interlocking corners, which are fairly strong and self supporting, BUT, we have also got 'pressures' or 'forces' from within the stack trying to push these corners outwards, especially if all the logs are round. Fusion 360 was used for the modelling and animations in the video.

If we wanted to go to the next stage of sophistication with our log stacking we'd want to interlock the corners themselves with the rest of the pile of logs.

One of the 'magic logs' is shown in the green circle and these are used to interlock the corners with the rest of the stack. We can also see how the logs in the corners are sloping downwards in the YZ and XY planes, which are effectively 'pushing back' against the forces within the centre of the stack.

Please note that it is not necessary to machine all your firewood into perfect cylinders! The best firewood for stacking is the stuff that has a square-ish profile and has been chopped from the rounds. To make life easier, select the square logs as much as possible for the corners and interlocks and use the round logs for the sides.

Any 'irregular' logs that are difficult to stack due to side branches etc are put into the centre of the stack, out of harm's way. They can, themselves, be stacked or just thrown in randomly.

Summary: Create interlocks between the corners and the rest of the stack and use the best shaped logs for the most critical parts of the structure.

Step 4: Tools and Materials

  • Logs
  • Large roll of clear pallet wrap
  • Roll of duct / gaffer tape
  • Pallets

Step 5: Start With the Corners

Carefully select logs that create good foundations for the corners. Square profiled logs are better. Try to get the logs sloping back into the stack a bit.

Step 6: Fill in Between Corners

It's important to build up the stack in a uniform manner, without building the corners too high too early or else they won't interlock with the rest of the pile.

Step 7: Build Up to Fourth Layer High

Step 8: Fill in Along the Sides

Step 9: Build Up Corners to Six High

Now we are getting to a more critical stage and it's important to try and keep the corners and sides as upright as possible.

Step 10: First Layer of Pallet Wrap

Wrapping up the first layer should stop the corners from popping out as long as they have been built reasonably well. The pallet wrap will help correct and alleviate any mistakes in the stacking.

Step 11: Fill in the Middle

The middle of the stack can be filled in with stacked logs, or if they are too irregular, just chuck them in randomly.

Step 12: Another Wrap at 12 High

The pallet wrap is one continuous run - it is not cut at all between layers.

Step 13: Another Wrap at 18 High

Get the wrap nice and tight without actually damaging it on any protruding logs.

Step 14: Random Fill the Top

A nice domed top is created at the end for spilling away rainwater.

Step 15: Wrap Over the Top

The top is wrapped over as shown and then another horizontal wrap is made to tie in all the vertical wraps. The final edge is tapped up with duct tape.

Step 16: Insert Ventilation Logs

The horizontal wraps can be pulled open slightly at the bottom of each section to create 'louvre / louver' vents. A suitably sized log is stuffed into the gap to hold it open.

If these louvres are not created, the moisture from the wood will not escape properly and condensation will form on the inside of the wrapping. Rain can't get into the vents as the gap is at the bottom.

Step 17: Graphs and Measurements

I've only had the sensors working for a few days so it's too early to see the long term humidity trends, but there is already some useful information to see.

  • Channel 1 (BLUE) : Sensor located in free air in shade under pallet.
  • Channel 2 (GREEN) : Sensor at top of wood pile just under the polythene.
  • Channel 3 (ORANGE) : Sensor right in the middle of log pile.
  • Channel 'IN' (RED) : Sensor on the west side of wood pile just under the polythene (gets afternoon sun).

The 'Greenhouse effect' is causing large temperatures to develop in the top and sunny side of the pile and there is enough air circulation for the hot air to find it's way into the middle and cause temperatures to rise there as well, especially during the middle of a sunny day, even though hot air does not normally want to go downwards. The humidity in the centre of the pile is also fluctuating which also suggests that air is moving around nicely.

If the logs in the centre were still wet (they were stacked after a rainy period) the humidity would be 100%, so obviously the water on the surface of the logs has gone, which I confirmed by manual inspection. Moisture inside the logs will come out much more slowly and I'd expect the humidity on channel 3 to slowly drop over the next 18 months. Watch this space for the next exciting update!

Just to prove that the logs are actually drying out, one freshly cut 'green' log was cut, weighed, labelled and placed in the centre of the stack and weighed again 6 days later. It had changed from 1.638 to 1.596 kg which is 2.6 % weight loss. I will weigh it again in about 2 weeks time, when it should have lost about 5% - It's going to be a parabolic curve when displayed in a graph as weight loss will be quick to start with and then progressively slow down to zero.

  • 0 days: 1.638 kg --------------
  • 6 days: 1.596 2.6% loss
  • 26 days: 1.480 9.6%

Have a look at the last graph above!

Step 18: Finished

Tape up any loose edges in the pallet wrap with gaffer tape or else the wind will catch hold of the edges and start to undo all our good work!

Key points:

  1. Create interlocking corners with logs sloping downwards into the pile slightly.
  2. Select the best shaped logs for the most critical parts of the structure.
  3. Create louvre vents in the pallet wrap.

Improvements

A tree fell down in a neighbour's garden so I sawed it up into rounds and stacked it with a chimney as an alternative to the louvre vents.

Please feel free to add suggestions for improving this technique in the comments section below. This instructable will be updated if I have missed anything.

Please in the competitions - top right - Thanks!

Comments

author
oragamiunicorn (author)2017-03-06

I can see that you've mastered your technique. But what is the benifit over just creating a crate of pallets and wrapping that, it seems like it would be much easier. Also could you improve ventalation by trapping short lengths of hose or drainpipe between the layers of wrap?

author

Just a shortage of pallets I suppose! I like your ideas, thanks!

author
Mjtrinihobby (author)2016-09-21

excellent write up as usual. You got my votes.

author
mpekar (author)2016-08-16

Nice instructable! I've been doing the same for many years, but I wrapped mine for stability when moving the pallets via skid steer. In doing so, I found I have to handle the wood one less time when using skids. I like your description of the science of the solar effect of seasoning the wood. Very thorough, good job.

image.jpeg
author
Tecwyn Twmffat (author)mpekar2016-08-16

Excelletn! Did you make vents for drying?

author
mpekar (author)Tecwyn Twmffat2016-08-16

Never found to be an issue. The top wasn't sealed up during the hot months and covered with a tarp during the winter before use. The rain "passed through" so to speak. My wood was mostly oak and required a lot of ventilation to season, and I remove as much bark as I can. I find the bark is a breeding ground for insects and rot and retains most of the moisture.

author
Venom8 (author)mpekar2016-08-18

Oak is a nice wood for an airtight but should be mixed with some other hard wood, (Maple,iron wood, beech, etc) as oak burns very hot and also much quicker than other hardwoods due to it being a very low density wood. I use oak in my wood furnace that heats my entire house (Continental Hybrid 150) but I always ensure to add other hardwood types in the mix..

author
ac-dc (author)2016-08-16

False assumption about wasted energy heating water in the wood. So long as the wood is dry enough to burn at a rate you find acceptable, the heated water coming off heats you just as well as if the wood were dryer. It is still heat, not wasted at all.

author
AlfieE2 (author)ac-dc2016-08-18

It takes exactly 1 BTU to convert each pound of water to steam (it is the fact that the BTU unit is based on). That BTU is absorbed in the process and does NOT produce any heat. Weigh a piece of green wood and compare it to its weight after a year of drying - you'll be amazed at the difference. Even "almost dry" wood loses a lot compared to completely dry.

author
Vyger (author)ac-dc2016-08-16

You can do a simple science experiment to find the facts about this.

Get some large cardboard boxes and run them through a shredder. (I shred cardboard all the time so a regular paper shredder with a 12 sheet capacity can do this). Using a scale divide up the cardboard into three piles. One pile is your control. It should be dry and free of any contamination. To the second pile add a measured amount of water and keep it in a plastic bag so the water gets dispersed evenly. After a day the cardboard should be damp but not wet. To the third pile add a lot of water, but not enough so that it will not burn.

Now the hard part, get some instruments that can measure the amount of energy given off when the cardboard burns. Some of the others might have some good suggestions here as to what to use.

Finally burn each pile and calculate how much energy each produces. They all three have the same energy content to start with. What conclusion can you draw from your results?

This would be a fun science fair project.

author
Tecwyn Twmffat (author)ac-dc2016-08-16

Thanks for your comment ac. I still believe that burning wet wood causes the heat to be lost. It's the 'latent' (which means 'lost') heat of evaporation, which effectively disappears and is no use to use unless it condenses back into water again. If the water trapped in the log was a gas then you would be correct, but it's all about the heat lost in the phase change from liquid to gas and water has a particularly high value.

author
namora (author)ac-dc2016-08-16

You present a non issue while make a false assumption about the physically held water. The energy to heat the water in properly stacked and dried wood is negligible but in poorly seasoned wood it can require so much energy that combustion cannot be supported. As to the heat of the steam/water vapor it is lost to its rise up the chimney or the atmosphere in an open fire, Contrary to popular belief heated air is of little use to most heating fires because of its immediate rise although there are a number of ways to utilise this often wasted heat and these would be excellent subjects for instructables. The real heating is done by infrared radiation.

However the problem with physically held water in wood is that the relatively low combustion temperatures burn less of the combustible gasses released by the heat of the fire and these unburned gasses combine with the water to form creosote which is deposited on the inner surface of the chimney creating a serious fire hazard.

Stacking cordwood against the side of a wooden structure is not recommended because this can be an invitation to termites and carpenter ants.

author
mpekar (author)2016-08-16

Also, as you can see by the third skid, my dogs found a chimp ink had moved in and assisted with the ventilation process by ripping off most of the wrap!

author
crankola (author)2016-08-16

Is your assistant Azealia Banks?

author
Tecwyn Twmffat (author)crankola2016-08-16

Yes - we were working on a new song together and did the log stacking in our lunch break.

author
crankola (author)Tecwyn Twmffat2016-08-16

!

author
Vyger (author)2016-08-14

I just thought of a fantastic user name, thanks to a phrase from you:

Chuck Random

author
Vyger (author)Vyger2016-08-14

And he could have a brother:

Phil Random

author
namora (author)Vyger2016-08-16

Would they perhaps work for the Bill Random Collection Agency?

author
Vyger (author)2016-08-14

I should get a hat like that for my assistant.

But then I suppose I should get an assistant first.

"Help Wanted ---- special assistant to Phil Hat, cousin of Phil Random. Must be good at wrapping things up."

I'm sorry. I must be in a punny mood today.

I have been cutting logs all week now. I have had 6 flat bed trailers of trees dropped off last week. A friend is helping to clear trees out for a new fence on a property by a golf course. They have been yanking them out of the ground with a front end loader and stacking them on the trailer root ball and all. It's a big mess now. Kind of like a giant was weeding his garden. But some of it is really good wood, and free is always a good price.

author
Tecwyn Twmffat (author)Vyger2016-08-14

That's cool! What species of wood did you get? ..... And whilst in the mood for puns ..... The 'burning' question is ..... Are you going to wrap your logs in pallet wrap?

author
Mindmapper1 (author)2016-08-14

Otherwise your wood will rot before it can be used

author

I've changed the title adding the word 'ventilate' to make it more obvious what's going on here. Thank you.

author
Mindmapper1 (author)2016-08-14

It is important that air can enter at the bottom of the stack and moisture and air can escape at the top

author

Yes - there is ventilation at the bottom within the pallet structure and the pallet wrap is pulled away from the sides to create rain proof louvre vents. There is no condensation in the top section so the vents do seem to be working well.

author
TomMcIn (author)2016-08-13

I use old pallets to keep the firewood from touching the ground. I have a large, open roofed area so just pile the wood on the pallets and use lengths of rebar mesh to keep the wood from spilling out.

Make sure there is lots of ventilation and that the air can get out the top. Otherwise, you will end up with piles of compost.

author
Tecwyn Twmffat (author)TomMcIn2016-08-13

The logs seem to be drying out very well although some compost would be useful too!

About This Instructable

24,420views

86favorites

License:

Bio: Ugly pirate roaming the seas in search of Treasure.
More by Tecwyn Twmffat:Arduino Cell Phone 4G Signal Booster / RepeaterSimple Manual Arduino 4 Axis Stepper Motor / 16 Channel LED Power ControllerFull English Breakfast
Add instructable to: