Originally Posted By Cpn_Ron:
They pretty much all say waterproof on their data sheet, at least what I've seen, though I think they're technically "water-resistant." I know SBC is/has been used for cisterns and other water storage; I honestly don't have much direct experience, just what I've seen others do. I'd use an additional waterproofer either way, just to be sure.
I looked into SBC and dry-stack pretty extensively while planning to build our next home. I think I've settled on ICF's now, though. I would fill the blocks with concrete anyway, might as well get integral insulation while I'm at it.
Stronger in some ways - yes. Typical mortar can crack under certain types of stresses. I don't recommend using typical mortar - something with a higher PSI rating would work better.
Interesting. Most of the ones I've seen typically used say water resistant, but that's stuff like sakrete. Turns out quikrete is using the phrase "waterproof" on their bags. Considering most people apply it far too thin to give a structure notably increased structural stability with even 1/2" thick exterior application, I'd still not trust it to hold up for the long term on its own. Any moisture getting between the block and SBC, and you'll get cracking during freeze/thaw in our climate.
Rusteerooster is probably fairly well versed in the speculative use of the trowel as well. I'd venture a guess he'd be like me and be more inclined to use a mortar joint construction, filled with concrete & rebar, and surficially sealed with a double application of sealant. That should do the trick so long as you use a strong, high PSI rated mortar.
My father's a structural engineer, and he hates my affinity for block wall construction... He's a huge fan of pre-stressed reinforced concrete panels.
I've seen good work done with ICF's on job sites, but make sure you don't skimp on the reinforcement & framing work to hold them in place. I've seen some shoddy contractors do a foundation wall, and insufficiently reinforced areas near the top of the wall cause things to shift or sway once filled heavily with concrete. Sometimes shifting over 1 to 2 inches at the top dimensions, and then they wonder why their floor beams and pre-stressed concrete flooring is too short and doesn't have enough overlap to be structurally stable.
Personally, I'm a huge fan of the hand-craftsmanship that goes into masonry work, but I'll readily admit it's not as structurally durable for the long term compared to some pre-cast reinforced concrete forms. What I like to do in my design work is to marry the two construction techniques together...
Like this Mausoluem I designed...
It uses precast reinforced concrete for extremely strong & durable structural integrity, and uses limestone masonry, CMU block masonry, and cast stone masonry for less critical structural and aesthetic purposes. There's no WAY that roof could be supported in the way it is using traditional masonry techniques. It requires substantial anchoring for wind / horizontal stresses, weight distribution including snow/ice loads, etc.
Cass Gilbert, a nationally famous Architect & Freemason at the turn of the previous century made a name for himself by becoming a pioneer of a certain construction technique. He LOVED stone masonry work, but the labor costs, and time requirements to cut & shape stones for use in building were incredible budget killers in the early 1900's! To build a Grand design using expensive stone was obscenely expensive to use expensive stone for structural work.
So he pioneered a steel suspension frame construction system. By using a steel frame to anchor thinner cut pieces of expensive stone, somewhat like a fascia, he was able to design massive buildings that are quite impressive. Such as the US Supreme Court building in DC, etc. He designed the chapel & other buildings in this cemetery out of old-style cut limestone masonry, and I had to find a cost effective way to match the look of his previous work in this new mausoleum.
As much as I like precast reinforced concrete for structural use, if I'm building a tornado shelter or safe room, I don't want other people to know about it. Having a large class-A straight truck or small crane rumble into the neighborhood would be an opsec nightmare...
I'd rather just build it with CMU's with high strength mortar joints, put rebar down the centers & fill with concrete.
Then I'd frame up and weld some rebar in the ceiling to the wall rebar, and do a poured concrete ceiling, with a couple sonotube / pvc pipes going out the top for ventilation.
I'd put extensive drain tile pipe around the exterior that 'daylight' or drain out on their own (don't want to rely on electricity for a sump pump setup).
I'd coat the entire exterior with a roll-on waterproofing sealant, and then a thick layer of tar sealant on the exterior walls & ceiling. Then stick some tar paper on top of the exterior ceiling, and another coating of tar sealant on the tar paper just for good measure.
Back-fill the structure with drain rock up against the side of the structure, using a separating fabric / membrane between normal dirt fill and the drain rock.
Keep the drain rock about 12" thick all the way around the structure when back-filling, and you'll likely NEVER have to worry about water issues.
Slower, labor intensive, and time consuming method, but it will work. With the right rebar it'll be incredibly structurally sound, and you can do it all yourself with minimal noise / visibility issues if you live rural enough and locate the structure in a place out of general view of the public / neighbors.