Stacking CMU blocks as shown above is a very weak configuration. If you go with this design, I suggest filling them with rebar and concrete to add strength. Since you are in California, the seismic rules for construction are likely to be the determining factor in what materials you can use.

ditto......have you looked at ICF? IMO....if I built anything in Ca, I would use ICF.

I agree- that's a very weak design in the photo. If I were building with CMU, I would add rebar and concrete anyway. CMU walls aren't all that strong, despite their appearance. They also have little to no insulation. Some people put insulation in the holes, but that does very, very little. Unless you're in a very mild climate, you'd have to add insulation on the inside, resulting in very thick walls. I'm another big ICF fan, and a mason could stucco the outside and strike fake grout joints to make it look like CMU.

I watched a mason applying 'brick' walls in FL. They put gray stucco on the wall, followed by brick red stucco, and struck grout lines through the red layer down to the gray layer. It looks exactly like brick!

California is a series of seismic zones (severity depending on location). CMUs are not a good material for lateral loads, and the build code will require substantial reinforcement designed to resist lateral loads. If budget is an issue, put CMUs out of your mind and use wood stud walls with shear walls where required by design and code. Stud walls with diaphrams are very resistant to lateral loads, when properly anchored and nailed.

I don't live in CA. But for my addition we are mimicking the house. Most of the walls will be block, but I believe there is rebar as well (I can see it in the phase we are currently on) as well as insulation. I'm sure people must do block all the time in CA and there must be a way to enforce it against earthquake damage?

"... I'm sure people must do block all the time in CA and there must be a way to enforce it against earthquake damage?..."

Yes, of course there is. The CMU cells are filled with vertical and horizontal rebar, tied together, and grouted solid. The rebar is tied into the foundation before the CMU are laid.

The OP's question was to compare the cost of CMUs versus conventional stud-wall framing. There's little question that stud-wall construction is faster and cheaper in seismic zones.

If one wants CMUs in a seismic zone, they can be done. It's only money!

"For cost we had heard they could be more expensive but that they could also save money on one aspect because you're not having to do drywall in the inside"

Then there won't be a possibility for electrical in that wall. Also, it will take a mason and a helper, to strike the joints on both sides. You want a real crafts man to strike those joints on the inside.

Avoid at all cost. They do not look good, permit no electrical, smell musty, and may develop cracks, allow insects. I would not go with any masonry wall w/o rebars. I like having both horizontal and vertical rebars.

How would you waterproof exposed cement blocks to the outside and maintain the look?

but that they could also save money on one aspect because you're not having to do drywall in the inside or worry about the outside materials (like wood siding).

Assuming of course that's the look you want, which we do. So they're basically done when they're installed. Oh also we found out they actually are insulated really well once the concrete gets poured inside them, you don't need to add insulation either.

Who told you that? I live in FL where 90% of all houses are built with cement block. You can bet that it is drywalled inside. And insulated. Cement block has very minimal insulation. If you heard otherwise, you heard wrong.

Cement block are not waterproof! How will you avoid water intrusion?

What I found...what looks like it should be inexpensive...is not.

The designer of the above pictured deathtrap stairs should be tossed off them just like his victim will be.

@Corlett: Those wooden stairs, the railing height - for an orangutan?

@jp fox: Go for it. Let us know how it turns out.

"@cpartist they are left exposed inside and out here all the time it's very common"

Then they would not be ordinary cement block construction obviously.

Here is Florida we live in CMU homes, but there are studs inside the walls where the electrical runs and drywall on the interior. Wood framing can be a feast for termites, house vermin and support mold. I would never go back to a wood frame home, especially in regions that suffer from drought.

Yes beveryly but the exterior is covered somehow to keep the water our. The first picture the op posted shows what appear to be bare cement blocks and he speaks of wanting that look. Cement block unto itself is very pourous and would leak almost like a sieve.

@virgil like this? We are installing block walls on my project (hopefully they are doing it right):

California code permits reinforced cmu walls in buildings.

r factor is of reinforced cmu is R1-R5 or something similar.

CMU is not used as foundation in CA, the blocks are placed on conventional concrete foundations.

Rainwater does not present a water intrusive issue. There is no water pressure against the cmu above ground. Sealants similar to paint can be used.

Rocky, in CA there should be vertical rebar for each "hole" of the cmu for a building. I do not know the requirement for a "wall". CalTrans requires rebar in each hole for freeway sound walls. There are requirements for max vertical length of the rebar. Example: length limit 6', to get a wall over 6' in height, an additional piece of rebar must be added, vs using single 10' piece.

Rainwater does not present a water intrusive issue. There is no water pressure against the cmu above ground. Sealants similar to paint can be used.

It doesn't? Why not tell that to my house I'm building. Tropical Storm Emily just blew in this morning and because our first floor cement block walls haven't been stuccoed yet, there is water intrusion through the walls.

Thanks Jim Mat. I'm in AZ. Do you know if rebar in each hole is best then for sound resistance? I'm guessing it's too late to add more rebar on my project...

re rainwater, CA code. The building in the OP is in CA, not FL.

My daughter lives in CA and while it doesn't rain frequently there, it does rain and sometimes quite hard too

Plain CMU walls are used for commercial buildings all of the time, in all different climates. It must be sealed properly, though, or water will soak through. They make concrete sealers that are very effective. The insulation factor for regular concrete is dismal, however. There are specialty air-entrained blocks that perform somewhat better.

Interresting

This is called reinforced concrete masonry and uses concrete masonry units (CMU). The reinforcing is both horizontal and vertical. The cores are filled with grout not concrete or mortar.

Standard units are used as a backup wall for veneers. Architectural units have a decorative weather resistant face. Adding insulation in a cold climate raises the cost and complicates the appearance. It might be fine in some parts of California.

IMO there are more attractive modern materials that are more energy efficient.

This is a 3-year old thread.

I suspect the OP has already found her/his answer, which is in seismic zones, with special structural requirements, it costs a lot more money to use heavy construction materials and make them laterally secure, than lightweight construction material such as wood framing.

Seismic forces consist of simultaneous forces in three axis, (x, y and z) exerting both compressive and tensile forces on structures. CMUs have inherent strength in compression but are comparitively weak in tension, hence the need for steel reinforcing in both horizontal and vertical planes.

Wood framing, properly designed for seismic activity, has strength in both compression and tension. And, for residential structures, it's cheaper and faster.