Pine wood underground cellar

Hello,

I am in the process of building a root cellar , having already dug the hole (4x3 meters) with roughly 1.5m depth. It will stick half of meter off the ground and I plan in covering it with all the excavated earth.

My concern is if it is a good idea to use wood(some black locust for the posts and beams, and pine for the roofing ,that should support all the weight of the earth). I will use a waterproof membrane on the exterior of the wooden stricture and some gravel for drainage between the earth and the membrane. I will also have a drainage pipe, and some passive ventilation pipes installed.

Given all of the above: Do you thing I will encounter rot/mould problems?
And if yes, what do you recommend?
Thank you!

I think your location would help us give a better idea. I think a humid coastal environment would require something different than a desert/arid one. So far, it is sounding pretty good IMO.

Hi Timothy,

Welcome to Permies.

Hi Timothy,

I m in a a mainland area, hills with forests and pastures. Sometimes is drought and sometimes it rains too much. Otherwise, tempered climate.

My thinking is.. if no water gets in from the top, the only source of water is the humidity inside.
If the inside air is humid enough to cause the wood to rot, it is probably too high anyway?

How wet is the soil in the hole?

Hi Nahara;
So for those of us in America, your excavation is apx. 9' x13' x 5' deep.
I like using black locust as posts and beams, but I have concerns with pine as roofing unless it is thick and straight-grained.
I would be very sure of proper drainage.
Are you building a north-facing entryway ( mud room)  with double walls and double doors?
Ventilation is a must or you will have mold issues.
Were you planning on covering your wood roof with anything before backfilling?

Have you considered a double-wall root cellar? A building inside your building with insulation between?
This would make for a very long-lived cool room.

Pictures please as you progress.

Sebastian Köln wrote:How wet is the soil in the hole?

Hello Sebastian,

Not that wet, but I have a lot of brown clay and blue clay, so I am thinking that the soil will hold onto moisture.

thomas rubino wrote:Hi Nahara;
So for those of us in America, your excavation is apx. 9' x13' x 5' deep.
I like using black locust as posts and beams, but I have concerns with pine as roofing unless it is thick and straight-grained.
I would be very sure of proper drainage.
Are you building a north-facing entryway ( mud room)  with double walls and double doors?
Ventilation is a must or you will have mold issues.
Were you planning on covering your wood roof with anything before backfilling?

Have you considered a double-wall root cellar? A building inside your building with insulation between?
This would make for a very long-lived cool room.

Pictures please as you progress.

Hello  Thomas,

Thanks for your comment.
The pine is round timber ,dry and peeled , diameter ranging around 4-6 inches.
I am building behind a building on the north side and I am considering installing 2 insulated doors.
The wooden roof I was planning to cover with a second hand truck canvas for waterproofing and afterwards to backfill.

I do not know what a double-wall root cellar is? I can't imagine.

I only have pictures with the dig(I have dug just a little deeper than the picture shows):

If you can cut it with a spade, the clay is probably too wet.
But there should be a good chance of drying it out over time with sufficient ventilation. If it does not get new water.

I am worried about water getting in through the top soil and then running down the walls. So I would remove the soil and ensure all water drains away from it.

Sebastian Köln wrote:If you can cut it with a spade, the clay is probably too wet.
But there should be a good chance of drying it out over time with sufficient ventilation. If it does not get new water.

I am worried about water getting in through the top soil and then running down the walls. So I would remove the soil and ensure all water drains away from it.

Ventilation as in passive ventilation or with a fan?
I was planning in adding gravel between the walls and the earth, și all that water that seeps through should go down the dravel into de drainage pipe... hopefully

The clay is going to be a little bit of a bear but I wouldn't let it slow you down. I'd highly encourage you to 'overbuild' the ventilation and drainage to be sure that it can handle the moisture from the ground.

This is not the same idea that you are utilizing, but this video shows a fella's root cellar and some hindsight realizations that he has which might be beneficial for your own planning.



Please post updates as you build, I'm learning with you!

Nahara Radu wrote:
Ventilation as in passive ventilation or with a fan?
I was planning in adding gravel between the walls and the earth, și all that water that seeps through should go down the dravel into de drainage pipe... hopefully

If you size the ventilation for passive operation, you can add a fan if it wasn't enough later.

If you build a fairly water-tight wall and floor, and have drainage from the bottom of the hole, that might work, yes.
I assumed the clay sides would remain as the walls.

EDIT: If you keep the clay walls they will keep the humidity very stable. If the walls separate the room from the earth, I would assume the humidity inside to fluctuate more?

It takes time but you could preserve wood with “Shou Sugi Ban”.  Char the wood, brush, wash, oil.

But (especially for something underground) I’m more interested in techniques using the existing soil material:  Earthbag, CEB, rammed earth, stabilized earth with 10% cement, stonewall, etc.

Hello, I m trying to keep a project -journal: Not much progress happened because of the lack of time, I only finished digging the drainage trench, 12 m long and with relative depth because of the slope. It leads to an old dried up well.

Started to frame the walls, this is what I have done so far. The posts are black locust and the beams are oak.

Hello again!

I have new updates on the root cellar project.

- I have completed the frame of the build
- built the retaining walls (3-4cm thick fir wood)
- added a standard membrane for water insulation
- put in place a 11cm diameter vent from the bottom to the top of the root cellar (the orange one in the pictures)
- added gravel to the sides to help with the drainage, among other functions

Plase see the pictures attached and give me some feedback. How can I improve?

I will continue by building the roof out of round timber fir (~10-13cm diameter) over it the same membrane and all the dugout earth.
Also I will add another vent on the top on the other side.

Hello there, some more updates:

Quick update: started to cover it with the excavated earth.

https://permies.com/t/223095/a/222164/IMG_20230916_171629.jpg

A bottomless bucket under the drain outlet might be convenient for a solar bilge pump

[quote=Burl Smith]https://permies.com/t/223095/a/222164/IMG_20230916_171629.jpg

A bottomless bucket under the drain outlet might be convenient for a solar bilge pump [/quote]

Thank you for your idea but I don't fully understand the principle . Could you make me a sketch? Or doodle? To fully understand,please? Thank you!!

This week's update contains:
- added more earth on the top and sides of the build
- dug out some stairs(very hard to dig dried up clay), in the future we are planning for some flat rocks for the steps
- made the inclined mold for the exterior door
Still a lot of work to be done.
The hygrometer points at 16° Celsius (60°fahrenheit) during the day, outside around 25, with the north side of the root cellar opened as can be seen in the photos.
The humidity is around 60% (59-64) which I hope will go down or I m guessing I will need to add a fan for venting. Any ideas on this part?