Electrical Shed/Bunker - Stick, block, or ICF? Lessons learned or suggestions?

[immortl]

I am going to be building a structure to house all of my solar electrical gear this Spring. I am trying to determine the best structure construction method for my particular area / use case here in Western MT. The structure will be located at the base of a large hill. It will house the batteries, inverters, MPPTs and associated gear. I'd also like to keep the 10kw diesel generator out by it, thinking up against one of the outside walls. To start with there will be 4 Midnite Powerflo16s and 2 Victron Quattro 10ks.

The area at the base of the hill where the shed/bunker will be located is open grassland facing directly south. My thought it to put up a 12'x20' structure. I have thought of 3 options so far.

1. Stick built shed using 2x6 studs, good insulation, and hang rock board internally to hang the gear on.

Ideally though, I think I'd like to sink the structure into the ground/hillside for temperature stabilization in both winter and summer. It can get down to -20ish overnight for a few days a year in winter and summer time temps can see a spike over 100 for 3 or 4 weeks a year. The area is referred to as the 'banana belt' of MT and is not as cold as other areas. I will say in the summer the sun is intense and hot. This is where the idea of a 'bunker' comes in. I recently picked up 2 older mini excavators to dig the pole mounts with so digging out an area for the electrical bunker ought not be an issue, or so I think. The soil is pretty darn rocky and I'm not yet sure how far down it is to bedrock.

2. Concrete block structure sunk into the ground/hillside - been watching videos on concrete block cellars. Sort of have an idea how to lay the blocks, but definitely need some practice. Seems you run rebar in the walls and fill with concrete afterwards. Saw one video where they filled the sun facing wall with vermiculite instead of concrete to keep the heat out. Then coat the outside and inside walls to waterproof it. Would I have to finish the inside walls with anything else? Then I'd use concrete anchors to mount everything on the walls?

3. ICF (Insulated Concrete Form) structure sunk into the ground/hillside - also been watching videos on ICF bunkers and homes. Seems it's like big adult legos, perhaps a lesser learning curve than concrete block? Again, some waterproofing at least on the outside before backfilling. What about the inside foam walls? Put up rock board? Would I sink anchors only into the rock board or do deeper through styrofoam and into the concrete wall portion?

Anyone have any thoughts or ideas on the above or other possible options I haven't yet considered? Anything you'd do differently if you built a dedicated electrical structure again?

Thanks!

 

[robbob2112]

Look in the up in smoke subforum. There is a long thread on building concrete or other flame proof ideal structures....

Also, think about geothermal heat pump for heating and cooling. Planning stage is best.

 

[skyking1]

I did an ICF daylight basement so I am a bit biased.
If you do put it in the hill, put it up the hill just far enough that you can dig drainage out from around the bottom of the slab to daylight easily.
I did slab on grade, then I had a nice surface to build the ICF walls. I put dowels into the concrete. Then I used Resisto waterproofing membrane down to the bottom of the slab on grade.
If you do good drainage, waterproofing is not going to have much damp on it ever.
It comes in 16" high blocks. Build it 5 rows high for 80".
Then frame up triangles east and west, and a rectangle north to make a south facing shed roof using I-joists.
Put standing seam metal on that and put panels on that too.

 

[quantum`]

I build exclusively with ICF, interfloor decks of Hambro D500, and InsulDeck roofs. Seismic safe, non-combustible, and exceptionally energy efficient. The 'therrnal inertia' of the concrete keeps an almost even temperature year-round. My current project is under a small plane flight path, but the homebuyers will hardly hear them.

Sure, you can screw the rock board to the 1" firring strips which are 1/2" below the surface, and usually spaced every 8". But you might be hanging heavy inverters. In this case cut out the foam where you expect the fastening areas to be and screw OSB over the holes. Concrete will fill the holes and you'll have rock-solid fastening points.

You will need to brace the walls; I own Giraffe brand, but you may find someone willing to rent. Just make sure they're the newer light-weight, not older bone-crushers.

Caution on ICF brands: There are about 72 brands out there and alot of junk; I recommend Logix.

If someone tries to sell you wood: Just Say No. (I've always been afraid of fire)

The only thing is ICF is so tight that the shed may overheat in Summer. I'd block out an area of ICF concrete with EPS, to allow for a duct or two, not to mention putting in all conduits before the pour.

 

[SilverbackMP]

Mine is stick built but only because there was an existing 12x12’ shed with an insulated garage door and concrete pad. Tore off the the sh!t squirrel damaged T1-11 siding and replaced with metal. Sprayed with foam (was doing my shop at the same time) and filled in with as much rock wool as I could stuff in. Inside walls all covered with plywood and then sheet rock for some more fire barrier. Built a a false floor that I also foamed. Installed a 9K Mitsubishi Hi2 Minisplit (bit over sized but the shed is home to 3x Sunny Boys, 4x Sunny Islands, batteries, and an undetermined amount of small scale server and switch stuff).

My alternate plan was to buy a small reefer van body.

My dream would be to have it all bunkerized or partially bunkerized. I’d go ICF if all brand new and money wasn’t a limit…with a tunnel to my underground lair under and beside my main house. Oh…and with a blast door big enough to roll at least side by side (or two) inside. Be cheaper just to buy a missile silo lol.

Colin Furze’s setup is also quite interesting (YouTube) as far as bunkers and tunnels and bat caves.

 

[rodrick]

I built my shed stick version due to the fact I have to move it to western Montana in about two months and my only concern is heating , during the summer with a small ac unit will be fine you will have plenty of power to run it

As far as fire resistance I used sheet rock covered with cement board

 

[dreancestere]

Probably not something you want to do. But, I thought it was interesting:

 

[kennyb]

I built a hybrid 12x14 ICF and stick frame. The bottom half is battery and inverter space. The upper half is a rainy day space for the nearby cabin. It's on an insulated raft slab. I put radiant tubing in the slab. I'll be using a propane water tank to heat the slab in dark winter and a ducted mini split to heat and cool for the rest of the year. - But in the meantime I've been running an 1800w electric heater I had in my empire of dirt. The upper floor isn't insulated or finished yet, and I've been able to easily heat the space to 15c when outdoor temps were -20c. It did however take ages and loads of energy to heat the thermal mass of the concrete.

I did it for pennies slowly acquiring the icf blocks from house builders left overs. The slab is r60 and made of reclaimed 4" roof XPS from a factory teardown.

Build as big as reasonably possible. I was avoiding a building permit and had to stay below 160sqft and it's been a struggle to fit everything to my electrical code requirements. Plan your services before hand. Coring out holes is a pain. I didn't rent braces, I used 2x4 and left over 3/4 plywood from my house foundation forms. I braced every ~2 feet on the outside. We poured in 2 lifts, on a "warm" December day (5c). it didn't budge. I'd suggest fiberglass rebar, it doesn't frostjack and is better thermally. Downside is you need to buy bends, you can't just field bend.

For fire resistance I covered the entire building in 2" of Rockwool comfort board (left over from my house), clad it in steel and inside I installed 2 layers of type c drywall.

 

[quantum`]

Rockwool Rules.

 

[skyking1]

@kennyb that is just great!

 

[immortl]

Look in the up in smoke subforum. There is a long thread on building concrete or other flame proof ideal structures....

Also, think about geothermal heat pump for heating and cooling. Planning stage is best.

Thanks for the pointer, I will check it out. I'll check out geothermal heat pump as well. The current smallish house uses a wood stove for primary heat with 2 propane wall heaters for backup. My sense is geothermal can be pricey to install, but it is something on my list to explore for the future house.

I did an ICF daylight basement so I am a bit biased.
If you do put it in the hill, put it up the hill just far enough that you can dig drainage out from around the bottom of the slab to daylight easily.
I did slab on grade, then I had a nice surface to build the ICF walls. I put dowels into the concrete. Then I used Resisto waterproofing membrane down to the bottom of the slab on grade.
If you do good drainage, waterproofing is not going to have much damp on it ever.
It comes in 16" high blocks. Build it 5 rows high for 80".
Then frame up triangles east and west, and a rectangle north to make a south facing shed roof using I-joists.
Put standing seam metal on that and put panels on that too.

Thanks for the suggestions. I am thinking about the drainage from the hill. I like the idea of a few extra panels on the roof. I did buy 4 extras...
When you say you put dowels into the concrete - are you referring to rebar up into the forms or something else that tied into the Resisto?

...

Sure, you can screw the rock board to the 1" firring strips which are 1/2" below the surface, and usually spaced every 8". But you might be hanging heavy inverters. In this case cut out the foam where you expect the fastening areas to be and screw OSB over the holes. Concrete will fill the holes and you'll have rock-solid fastening points.

You will need to brace the walls; I own Giraffe brand, but you may find someone willing to rent. Just make sure they're the newer light-weight, not older bone-crushers.



If someone tries to sell you wood: Just Say No. (I've always been afraid of fire)

The only thing is ICF is so tight that the shed may overheat in Summer. I'd block out an area of ICF concrete with EPS, to allow for a duct or two, not to mention putting in all conduits before the pour.

So yes, most things going on the wall will be heavy. If I'm understanding correctly, cut away inside wall foam in areas where I expect to mount gear and then screw some osb over the cutouts. When the concrete is poured, it'll fill in and when I remove the OSB, I'll have concrete at the same level as the foam wall. Would I want to target mainly where the actual screws/mounts would go or the whole backsize of the gear? I'm thinking I would be tempted to pretty much cut away an entire wall's worth of foam inside.

Caution on ICF brands: There are about 72 brands out there and alot of junk; I recommend Logix.

I haven't yet dug into the ICF brands and really appreciate your suggestions and tips. This is very helpful.

The only thing is ICF is so tight that the shed may overheat in Summer. I'd block out an area of ICF concrete with EPS, to allow for a duct or two, not to mention putting in all conduits before the pour.

The possibility of overheating in the summer is a concern. I was thinking I can add in a small minisplit if necessary and definitely some venting. The structure would run long wise west to east, so a 20' wall would be somewhat exposed to the sun, depending on how far down I am able to sink it. I could maybe position it behind the 3 pole mounts (each with 16 400 watt panels) which would shade it some. I sort of wanted the mounts a bit further down the pasture and up against the hillside if not a little bit up the hill. I need to see how I can maneuver the mini excavators and still dig down 7 or 8 feet. If I can manage to dig the mount foundation holes slightly up the hillside, that would be ideal.

Mine is stick built but only because there was an existing 12x12’ shed with an insulated garage door and concrete pad. Tore off the the sh!t squirrel damaged T1-11 siding and replaced with metal. Sprayed with foam (was doing my shop at the same time) and filled in with as much rock wool as I could stuff in. Inside walls all covered with plywood and then sheet rock for some more fire barrier. Built a a false floor that I also foamed. Installed a 9K Mitsubishi Hi2 Minisplit (bit over sized but the shed is home to 3x Sunny Boys, 4x Sunny Islands, batteries, and an undetermined amount of small scale server and switch stuff).

My alternate plan was to buy a small reefer van body.

My dream would be to have it all bunkerized or partially bunkerized. I’d go ICF if all brand new and money wasn’t a limit…with a tunnel to my underground lair under and beside my main house. Oh…and with a blast door big enough to roll at least side by side (or two) inside. Be cheaper just to buy a missile silo lol.

Colin Furze’s setup is also quite interesting (YouTube) as far as bunkers and tunnels and bat caves.

Don' t know if I'll ever quite get that far, but the idea of a complete underground bunker complex is extremely appealing. I like your idea of putting server rack and switching gear out there. I could put my ESXi host and NAS and whatnot out there too.

I built my shed stick version due to the fact I have to move it to western Montana in about two months and my only concern is heating , during the summer with a small ac unit will be fine you will have plenty of power to run it

As far as fire resistance I used sheet rock covered with cement board

Whereabouts in western Montana are you heading towards? I am outside of Plains.

I built a hybrid 12x14 ICF and stick frame. The bottom half is battery and inverter space. The upper half is a rainy day space for the nearby cabin. It's on an insulated raft slab. I put radiant tubing in the slab. I'll be using a propane water tank to heat the slab in dark winter and a ducted mini split to heat and cool for the rest of the year. - But in the meantime I've been running an 1800w electric heater I had in my empire of dirt. The upper floor isn't insulated or finished yet, and I've been able to easily heat the space to 15c when outdoor temps were -20c. It did however take ages and loads of energy to heat the thermal mass of the concrete.

I did it for pennies slowly acquiring the icf blocks from house builders left overs. The slab is r60 and made of reclaimed 4" roof XPS from a factory teardown.

Build as big as reasonably possible. I was avoiding a building permit and had to stay below 160sqft and it's been a struggle to fit everything to my electrical code requirements. Plan your services before hand. Coring out holes is a pain. I didn't rent braces, I used 2x4 and left over 3/4 plywood from my house foundation forms. I braced every ~2 feet on the outside. We poured in 2 lifts, on a "warm" December day (5c). it didn't budge. I'd suggest fiberglass rebar, it doesn't frostjack and is better thermally. Downside is you need to buy bends, you can't just field bend.

For fire resistance I covered the entire building in 2" of Rockwool comfort board (left over from my house), clad it in steel and inside I installed 2 layers of type c drywall.

Your post has got me scheming. The small 'house' that is on the property is newish and nice inside and has all the modern conveniences, but it's actually 2 Amish sheds put together and finished off as a traditional house inside and is not on a permanent foundation. I want/need to have something on a permanent foundation to make the property 'real estate' for when the interest rates drop. I am liking the idea of a 2nd story above. All I need is a simple room, doesn't need running water.

Thanks again to everyone, I appreciate the great insight and very useful information.

 

[doing it different]

You could partly bury a shipping container. Thinking to do a cold storage/ celler that way

 

[Brucey]

You could partly bury a shipping container. Thinking to do a cold storage/ celler that way

They can't take any pressure from the sides so be careful.

 

[doing it different]

They can't take any pressure from the sides so be careful.

Yeah some reinforcing might be smart. But if you backfill with gravel it will be minimal.
You will want to put some kinda waterproofing on it, and really good drainage

 

[quantum`]

When you say you put dowels into the concrete - are you referring to rebar up into the forms or something else that tied into the Resisto?

Dowels should have an L-bend and wired into the footing rebar. Don't just stick straight rebar into the wet concrete if you want strength. You can hold them straight with a 2x2 wired to each up high.

Also consider an Ufer ground in the footing. They're very effective, that is unless you use FastFoot or some other clunky alternative.

So yes, most things going on the wall will be heavy. If I'm understanding correctly, cut away inside wall foam in areas where I expect to mount gear and then screw some osb over the cutouts. When the concrete is poured, it'll fill in and when I remove the OSB, I'll have concrete at the same level as the foam wall. Would I want to target mainly where the actual screws/mounts would go or the whole backsize of the gear? I'm thinking I would be tempted to pretty much cut away an entire wall's worth of foam inside.

Correct. You could do the whole back panel. Just make sure that OSB is screwed well into the firring strips as, the farther down the wall the hole is, the more pressure, and blowouts are likely and a real mess.

The concrete would help with heat dissipation of the inverters.

 

[immortl]

Dowels should have an L-bend and wired into the footing rebar. Don't just stick straight rebar into the wet concrete if you want strength. You can hold them straight with a 2x2 wired to each up high.

Also consider an Ufer ground in the footing. They're very effective, that is unless you use FastFoot or some other clunky alternative.

Ok, got it, that makes sense to me. I'll be exploring the Ufer ground. Seems like that could be the common single ground for the electrical system and the buildings in the area based on my quick reading.

Correct. You could do the whole back panel. Just make sure that OSB is screwed well into the firring strips as, the farther down the wall the hole is, the more pressure, and blowouts are likely and a real mess.

The concrete would help with heat dissipation of the inverters.

Ok, that gets me excited. Good to know I could do the entire back wall that way. When you say screw the OSB in to the firring strip and mention to be careful of blowouts, I'm thinking drill some holes and use fender washers and bolts to add more security. Coat bolts with something so I can back them out after concrete sets, the back washer and nut would just remain in the concrete while I could remove the bolt and the front facing washer...

 

[immortl]

@Brucey @doing it different

I am confident that at some point I will have some sort of at least semi sunk if not fully sunk container up there. In my head I would frame out the interior for support. Somewhere along the line a long while back I picked up that they're not all that stable with regards to side pressure and I've always figured I'd do some interior framing to reinforce them.

We had looked at a property once that had a buried short bus. Ever since the wife to be has wanted an underground bunker, and tunnels, and secret escape hatches, and air filtration, etc... I also foresee a 100yd underground rifle range. Used to shoot at one in the Flathead valley and it was great for sighting in the rifles, no wind.

I really wish I had started all this 20 years ago.

 

[HarryN]

Suggestions

1) Build it 3x as large as you think that you need
2) Hills are not necessarily stable and can have slides
3) A lot of water and mud can come down a hill, both on the surface and just below the surface, so drainage is a big deal. Minimum of 12 inches of drain rock, and then 6 inches of a base rock or 1/4 x dust.
4) Generator - put it inside of "something" to help contain the noise and protect it from the elements. It needs to work in the worst of times.
5) Use a material that will not rot when snow is piled up on one side 6 ft high

 

[doing it different]

@Brucey @doing it different

I am confident that at some point I will have some sort of at least semi sunk if not fully sunk container up there. In my head I would frame out the interior for support. Somewhere along the line a long while back I picked up that they're not all that stable with regards to side pressure and I've always figured I'd do some interior framing to reinforce them.

We had looked at a property once that had a buried short bus. Ever since the wife to be has wanted an underground bunker, and tunnels, and secret escape hatches, and air filtration, etc... I also foresee a 100yd underground rifle range. Used to shoot at one in the Flathead valley and it was great for sighting in the rifles, no wind.

I really wish I had started all this 20 years ago.

Where I am we have clay. The settling is what pushes like crazy. Once its settled it's not bad. I would have 2x4 across the middle and support the walls outward.

 

[skyking1]

If you can get cheap leftover ICF like @kennyb did, that would drive the bus for me. Nothing so moderating as putting a bunch of a structure underground.
I would not cut out the foam from the inside, myself. There is no reason not to stand things on the concrete floor for the bulk of the support, so no need to go nuts hanging all the weight on the wall. I would not want to lose that insulation.
Sheet rock and tape, and then put CDX plywood on it and anchor back into the concrete rather than the plastic lath in the ICF if you want it stronger.
3/4" ply is nice to hang most things on and something really heavy can get an anchor into the concrete.
I'd make an approach out of ICF from the down hill side and roof that so it looks like a root cellar.
frame up the shed roof and cover the sides and back with metal too.

 

[rodrick]

Whereabouts in western Montana are you heading towards? I am outside of Plains20 miles west of kalispell

30 miles west of Kalispell south of hwy 2

 

[niktak11]

You'll definitely need a mini split if it's a tight insulated building. A big system could be putting out space heater levels of heat.

 

[skyking1]

set mostly below grade, you can vent a lot of heat out the gable ends during the day.

 

[quantum`]

Ok, that gets me excited. Good to know I could do the entire back wall that way. When you say screw the OSB in to the firring strip and mention to be careful of blowouts, I'm thinking drill some holes and use fender washers and bolts to add more security. Coat bolts with something so I can back them out after concrete sets, the back washer and nut would just remain in the concrete while I could remove the bolt and the front facing washer...

Keep in mind that when you fasten the OSB it will be to the built-in firring strips. No need to coat the screws, in fact that would weaken pull-out strength. You'll see when you get them. Drywall screws, or similar phosphate-plated or epoxy screws are best. If you set the load center into the concrete remember to make it 5/8" proud of the EPS to allow for the thickness of drywall.

Cut wire races in the EPS with a chainsaw. Three wires max per race. To recess outlet boxes, Windlock makes a special ICF heat-wire tool with different widths for water lines, outlet boxes, etc.

I don't bother with fender washers, just alot of screws, and for larger holes like a load center I screw 2x4 braces across to prevent blowouts. You'll be sorry if you don't...

Some electrical inspectors require you to cover the back of a load center if you're going to cut a hole and set it in the concrete. They claim it is base (as opposed to acidic) and will attack the steel. Personally I think that's specious but I do what they say.

When you do a cutout for something as large as a load center, you are cutting the webbing between the outside EPS and inside EPS. This compromises the strength of holding the walls together. So on the outside screw a 4'x4' OSB to hold the EPS from blowing out the back.

 

[immortl]

You'll definitely need a mini split if it's a tight insulated building. A big system could be putting out space heater levels of heat.

OK, this is one of the things I wanted to suss out in this thread, but didn't ask directly. My purpose of sinking the structure into the hillside/ground is to try to take advantage of temperature moderation.

While ICF seems easier to install/build with, might uninsulated cinder blocks achieve the desired temperature moderation a bit better?