Bottom of the Stack Blues

[BamaScroungr]

Since I've reached the bottom of my first three stacks I've noticed my wood is hissing and spitting a lot more moisture than it was a month ago, when the stacks were taller. Is this normal?

 

[Cburke]

Are your stacks/wood off the ground on pallets or something similar? If not this could be causing this. Also in my opinion wood on the bottom of a stack doesn't dry as well. I have had some bigger pieces hiss and sizzle but for the most part they are dry.

 

[BamaScroungr]

Yes, I forgot to mention my stacks are all on pallets. Glad to see someone else has similar issues. Maybe I need to get my stacks higher off the ground?

 

[bholler]

Are your stacks covered?

 

[Ashful]

Yes, I forgot to mention my stacks are all on pallets. Glad to see someone else has similar issues. Maybe I need to get my stacks higher off the ground?

I just rotate the stack when I move it up to the house. What was on top of the stack in the wood lot ends up in the bottom of the rack at the house, and vice versa. I may get a hisser for the first day or three after moving a stack, but that's about it.

 

[LocustPocust]

Yes it's normal. It's close to the ground so it doesn't dry as well and It gets wet from splashing when it rains hard.

One of my stacks was 3/4 empty so I moved what was left onto another tier. Very dead barkless Black Cherry. It seems pretty dry but from experience I'll let it sit on top of another stack for a few weeks.

 

[Poindexter]

Yup, normal. Higher in the stack = dryer wood. The very dryest stuff is at the very top where it is covered on the top and both sides by your overhang. The wettest stuff is at the bottom where splashing rain drops and heavy morning dew can get at it.

If you are running a big enough inventory you can put the bottom two layers of splits that have one summer of seasoning time on them on top of a fresh stack of green that hasn't started seasoning yet. Come fall the top two rows will have two years of seasoning on them and ought to be pretty darn dry. Not a fan of restacking myself.

Alternatively you could raise your pallets up off the ground with cinder blocks or railroad ties. You could also consider experimenting with putting a layer of plastic on your pallet floor before the wood goes on. That can bite back if the plastic at the bottom ends up being the floor of a puddle instead of the ceiling of a vapor barrier. Worth thinking about anyway.

 

[maple1]

You can improve things in the future by getting the pallets up off the ground on blocks or splits or whatever. The higher the better. I also run around mine with the weed whacker a few times in the summer to keep grass & weeds away from the bottom so air can get in under there - and grass & weeds also constantly give off moisture. Or you could go around once or twice with Roundup.

 

[Firefighter938]

I stack about 2 miles away from my house at my parents. Then I move the wood in the fall to my house. The benefit is rotating the stack to get some of those bottom pieces mixed into the middle a chance to dry out. I also stack about two days worth of wood on either side of the hearth. I burn one side down and then other side gets the added benefit of drying next to the stove. Once I get a rotation established all the wood has a chance to dry for at least a day. Maybe even 2 or 3 days this year.

 

[gzecc]

I now put smallest splits on the bottom of all my stacks. Used to put largest on the bottom for structural reasons. I switched it for seasoning reasons.

 

[BamaScroungr]

Well thanks for the input guys, I may try something different this next season.

 

[Applesister]

I put paver bricks under my pallets, mostly to level them and try to save the pallets a little. But it gives them another little air pocket.
Theres a little bit of rotating involved and maintenance with stacks you keep outside.
Obviously if you rotate to a shed you're somewhat conscious of where the bottom of the stacks will go.
Or to another spot by your back door.
You can make a mental note of the bottom layer and not really worry about it, or you can fuss.
I fuss a little bit but I dont let others know. I do it when no ones around.
I hate defending myself for being OCD.

 

[Ashful]

Alternatively you could raise your pallets up off the ground with cinder blocks or railroad ties. You could also consider experimenting with putting a layer of plastic on your pallet floor before the wood goes on. That can bite back if the plastic at the bottom ends up being the floor of a puddle instead of the ceiling of a vapor barrier. Worth thinking about anyway.

Good idea, but I would think you'd want that vapor-barrier plastic UNDER the pallets, not over them. You want an air space between the plastic and the firewood.

 

[HItz]

I have gravel under my pallets, maybe 2 inches of gravel. Not sure how long it'll last before it is covered in wood droppings but right now it seems to work pretty well.

Most of my other wood has the cinder block with landscaping timber setup so the first row of splits are about 12 inches off the ground (8 inches of cinder block plus 4 inches of landscaping timber).

 

[Ashful]

I have gravel under my pallets, maybe 2 inches of gravel. Not sure how long it'll last before it is covered in wood droppings but right now it seems to work pretty well.

Most of my other wood has the cinder block with landscaping timber setup so the first row of splits are about 12 inches off the ground (8 inches of cinder block plus 4 inches of landscaping timber).

I'll be interested to hear how this holds up after a few years. Have always debated doing the same for my stacks.

 

[Poindexter]

Good idea, but I would think you'd want that vapor-barrier plastic UNDER the pallets, not over them. You want an air space between the plastic and the firewood.

I have read that a lot, believed it for a while. At my house, I am not sure that is true.

How come the split 6 rows up, with 5 layers of other splits between itself and the pallet gets dryer than the one at the bottom on the pallet with the "better" airflow?

 

[Poindexter]

Heretical huh? But look at al these folks in this thread from all over the continent seeing the same outcome. Why is that?

I have some hypotheses, and some new construction based on my hypotheses, but I don't "know" why.

Observation: The bottom couple layers of splits in a sizable stack are generally a little wetter than the ones above them, even with an airspace under the wood to get it off the ground.

Possibilities:

1. splashing rain drops, heavy ground hugging early morning dew. Solution, elevate stacks. Observation at my house, helps, but not the whole story.

2. hot air can carry more water vapor than cool air. hot ait high in the stack can carry away more water than the cooler air at the bottom. Solution, Katy bar the door... gotta go

 

[iron]

i know our local meteorologist/weather geek always talks about how cold air pools on the ground. so, even though temperature measurements are taken at 6ft off the ground (i think), you're likely going to have temps several degrees cooler at the ground surface. so, that could contribute to the bottom row not drying out as quickly

 

[Longstreet]

i know our local meteorologist/weather geek always talks about how cold air pools on the ground. so, even though temperature measurements are taken at 6ft off the ground (i think), you're likely going to have temps several degrees cooler at the ground surface. so, that could contribute to the bottom row not drying out as quickly

That's only true in certain environments/situations - periods of cooling and in closed areas (such as buildings) being two examples. In open spaces in times of rising temperatures (exactly when our stacks are drying the most - warm summer days as the sun shines), temperatures increase as you get closer to the ground.

Hot air does rise, but when that heat is being provided by a medium (the ground in our example) you cannot get hotter temps as you move farther away. Remember, the ground heats the air, not the other way around. The top of racks dry faster because they get more sun and aren't in proximity to ground moisture. It has little to do with hot air rising.

Your weather guy isn't incorrect, you just cannot apply his statement to drying stacks of firewood in the open.

 

[Paulywalnut]

I use Box Elder on my first rows just for this reason. Moisture is always going to be higher in the lower part of the stacks unless you're talking 3 years in the wind and sun.

 

[Wood Duck]

I find the same thing in my stacks - the bottom few layers are always less well seasoned than wood higher up. I think it is because it is a little windier the farther from the ground you go, and this is especially important on moist, calm days when the ground is a source of moisture. Air close the ground is more still and more moist, and that makes the bottom of the stacks dry out more slowly than the top of the stack.

 

[Poindexter]

I have another hypothesis, can't prove it. I _think_ the thermal mass of the sunlight heated woodlpile pumps water vapor out of the ground, and that same water vapor is very happy to condense on the nearest surface dry enough to accept it.

Couple pics. My smoker is running at 225dF today. Note what is happening to the snow around the base of the unit.

 

[Poindexter]

And another example of what I THINK might be the thermal mass of the wood pile attracting water vapor is over in a another thread. I couldn't see uploading the pics twice, so here is the link.

https://www.hearth.com/talk/threads/solar-cord-wood-kiln-operation.152699/#post-2061218

Interesting thread here, common problem over a wide area, I wish we had a physicist member.