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Diy: Underground bunker/root celler question

14K views 12 replies 8 participants last post by  Ricky-From-Dallas 
#1 ·
I know this has been covered a ton of times on here and I'm sorry to bring it up again. But as I was scrounging the internet and the forums here I thought of something. Now don't totally flame me for this but what about building a bunker/root cellar out of wood. Basic layout as follows. The box will be seven feet wide eight feet tall and eleven feet long. The shaft for the entryway is two feet wide by four feet long by two feet high. Basically you would build a frame out of 2x6-8's with a width of approx 2ft between the frames then u would run 2x6-8's horizontal to hold the frames together. Then use 4x8 sheets of MDF or plywood to cover the frame. Then use a 6 mil or better plastic sheeting to cover the whole thing too keep water out. Cut ventilation ducts to keep moisture down and i think this might work. What say y'all with more knowledge than me.
 
#6 · (Edited)
Something's we encountered in Iraq were pretty well built and had very similar structure. What you describe is more of a spider hole than a bunker. I would use it as such.

For a root cellar you want to keep your items a foot off the ground at least and not have ladders for rodentia. So built in shelves is a good idea. Your dry goods need to be in the very back away from the opening, doesn't matter if they're Mylar sealed, atomic lidded, and desiccant packed. Moisture will over power all of that when left in a damp hole such as you propose. Also don't plan on living down there. Treated lumber or not the rot will grow, it just won't grow on the wood. The environment is perfect down there for a type of trench foot, this isn't just the normal stuff either, it's the airborne type. Depending on your region depends on the severity. Arizona, this probably wouldn't be a big issue. PNW or AEC you're going to have major problems. If you can do it out of cinder brick or concrete. You'll be much happier. Also don't give yourself only one entry and egress point. Have two at least. If I were building mine over I'd have four, one for every cardinal direction with labels on each and an azmuth to where they are pointing. But as it sits I only have two. One North at 6400 mils and one West at 4950 mils. Just how the construction happened. That's not including the entry point at 1635. So from experience. Do it in brick and mortar. The one I built is nothing more than an OP LP now with pill slits in it's sides. If you had to live in it, and you would have to, you wouldn't want to stay long for the exact health reasons above. These things attract and trap water. For our water barrier we used excess HDPE at a 1/4" to line the exterior frames. We used crating for the floor which gives you about a 1/2" rise and keeps you quiet when walking around, and still wound up with about 8" of water for no apparent reason.

By all means build it, it's a valuable resource to have and exploit. But learn from my mistakes. Put a drain in the floor with a down pipe that leads away from your foundation, slope the floor towards it, about 2* in all directions, and build with cement.

Remember mass stops just about everything. Including water.
 
#9 ·
Good to go then. Use whatever in that case, we didn't see a whole of water damage issues in Iraq, if any that I can recall. The climate seems to have the same humidity level as desert Nevada. I would still recommend at least pooring a slab with a drain. The wise man built his house on a rock, or cement. You're board feet is going to get pretty costly unless you're using scrap rail road ties. Simply because you have to keep all the side panel dirt at bay. We got lucky and have ties in our little slice of deasease ridden paradise. It doesn't rain a ton there, I'm guessing but you still want to have slopes for your entrance portal and exit. I highly recommend having two points at least. If any human is going to be down there for any length of time. You also have to consider freezing and thaw expansion with lumber and subterranean living. Wood likes to move around a bit. Nails and screws move with it.

How much stuff, square feet wise, are you looking to store. Don't list your entire inventory. I wouldn't. Just give yourself the basic idea. We cut ourselves really short on moving space in there. A two foot opening doesn't give you any room to get anything down there. I don't even think I would fit with my clothes off and greased up. You may want to consider a wider entry, just for ease of access. Possibly three feet. The average male is 60" tall and 28" across. That extra 10" might come in handy for movement in and out with arm loads of stuff.

Im not tryin to tell a feller how to sheer his sheep. Just tryin to give a helping hand.
 
#10 ·
I would forget the 2X posts and rafters and I would never use MDF below grade. I would use 4X6 posts and 6X6 rafters. Maintain your 24" post and rafter spacing. For siding I would use 2X6 tongue and grove. All lumber should be pressure treated and all fasteners should be rated for PT lumber. I would paint the dirt side with 2 coats of foundation coating. While the second coat is still wet, I would wrap the sides with 6mil or heavier plastic sheeting. Insure the plastic sheeting extends at least 24" past bottom of the wall. I would slope this down 6-8" and out 24". At the low point install a 4" ABS plastic drain tile that gravity drains away from your cellar. After the sides are wrapped, I would cover the top with the same plastic sheeting. Insure the top covering drapes at least 2 feet down each side and use foundation coating to seal the top to the sides. 2X4's should suffice for you entrance. Back fill your hole with rock free fill dirt or sand. Sand is best. (rocks can cut the moisture barrier)

Next item of business is to position this or erect barriers to prevent vehicular traffic over top of the cellar. Not really fun to drop a truck, tractor, or 4-wheeler in to your cellar.

In Nevada's climate, it should last a long time.

I am neither an engineer nor a contractor so my thoughts are just that. My idea of what would work.

PS I just noticed your drawing has the rafters/joists attached to the posts. Place the rafters on top of the posts and fasten them in place with Strong-Tie Straps. If you just attach the rafters to the side of the post, the fasteners are holding all the weight on the rafter. This way the post is supporting the weight.
 
#12 ·
Plastic is not going to stop humidity and condensation. The wood is going to rot and mold over time. If you go with pressure treated wood it would last longer but cost increases. Paint should help too but again cost increase.

I would go with reinforced concrete/blocks. You're still going to need some type of draining system no matter what.
 
#13 ·
Can always try green stuff

There's a new green chem that you can apply to traditional pressure treated lumber to make it more resistant to decay. They've got it at HomeDepot. Also, Marine Grade wood will work very well. The original floor that's in our underground shelter is Marine grade plywood, the same stuff they make fishing piers and put on shipping containers because it resists water better. Its a little more expensive of course, but it works great.
 
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