How does one build a house out of cement blocks?
March 3, 2021 2:45 PM Subscribe
Can someone please direct me to a straightforward step-by-step guide to building a cement block house that meets California building code?
I feel like there should be some good how-to resources somewhere on the internet, but all I can find are DIY retaining wall instructions and videos from other jurisdictions (e.g. Jamaica).
Just a small 1-story house, in the 300-700sqft range. I know there's rebar involved, and mortar, and maybe concrete or insulation filling the voids in the blocks, but I don't know how it all connects, and how much of each component is necessary.
So: How do you build the walls of a house from concrete blocks?
I feel like there should be some good how-to resources somewhere on the internet, but all I can find are DIY retaining wall instructions and videos from other jurisdictions (e.g. Jamaica).
Just a small 1-story house, in the 300-700sqft range. I know there's rebar involved, and mortar, and maybe concrete or insulation filling the voids in the blocks, but I don't know how it all connects, and how much of each component is necessary.
So: How do you build the walls of a house from concrete blocks?
It's a better question to ask your building department. It's possible that you are not qualified to design or build a masonry structure in California intended for use as a residence. If you are, they'll probably be able to tell you how to do it, only because there's a prescriptive code covering it. That's how my building department in San Diego had detailed instructions for building retaining walls of varying heights. Your library would be a great place to look, but you're going to be talking to the building department at some point, so you might as well do it now.
posted by LionIndex at 3:34 PM on March 3, 2021 [8 favorites]
posted by LionIndex at 3:34 PM on March 3, 2021 [8 favorites]
There's a lot to cover here, so I'm only going to cover a few hopefully-useful points.
First of all, you absolutely must contact your local building authorities (as noted above) prior to doing anything; if you do not, and they find out you've built something that doesn't meet their rules, they can force you to tear it down at your expense. In fact, even if you've built something that technically meets their requirements, and you cannot prove it to their satisfaction, they can force you to tear it down. In both cases they can (and usually will) assess various fines and fees.
They will have requirements regarding where a structure can be built, how that structure relates to other nearby structures, what foundations are allowed, what types of wall construction are allowed, where electrical outlets are allowed, how many smoke detectors are required, and so on, and so on, and so on. If you can find an older copy, Building Codes Illustrated may be helpful in getting an overview (this is the 2018 version; the 2021 version is coming soon, and of course other websites have the book for less money).
Note that building codes are updated every few years, but each jurisdiction may update their own version at varying times, and may also add local amendments, all of which are further reasons to get in touch with your building authorities.
Having said that, the trade term for most (not all) "concrete blocks" is CMU -- Concrete Masonry Unit. Searches using this term will be more useful, I suspect.
The relevant trade organization is NCMA, which has a bunch of relevant technical information on their website.
Unless you are in an unincorporated area, it is very likely that you will be required to submit plans that have been stamped by a professional engineer (or even a structural engineer), so getting deep into design requirements may not be useful expenditure of your time -- this is another reason to check with your local authorities.
posted by aramaic at 3:48 PM on March 3, 2021 [9 favorites]
First of all, you absolutely must contact your local building authorities (as noted above) prior to doing anything; if you do not, and they find out you've built something that doesn't meet their rules, they can force you to tear it down at your expense. In fact, even if you've built something that technically meets their requirements, and you cannot prove it to their satisfaction, they can force you to tear it down. In both cases they can (and usually will) assess various fines and fees.
They will have requirements regarding where a structure can be built, how that structure relates to other nearby structures, what foundations are allowed, what types of wall construction are allowed, where electrical outlets are allowed, how many smoke detectors are required, and so on, and so on, and so on. If you can find an older copy, Building Codes Illustrated may be helpful in getting an overview (this is the 2018 version; the 2021 version is coming soon, and of course other websites have the book for less money).
Note that building codes are updated every few years, but each jurisdiction may update their own version at varying times, and may also add local amendments, all of which are further reasons to get in touch with your building authorities.
Having said that, the trade term for most (not all) "concrete blocks" is CMU -- Concrete Masonry Unit. Searches using this term will be more useful, I suspect.
The relevant trade organization is NCMA, which has a bunch of relevant technical information on their website.
Unless you are in an unincorporated area, it is very likely that you will be required to submit plans that have been stamped by a professional engineer (or even a structural engineer), so getting deep into design requirements may not be useful expenditure of your time -- this is another reason to check with your local authorities.
posted by aramaic at 3:48 PM on March 3, 2021 [9 favorites]
Response by poster: I will build to code and with permits. I have prior experience as an owner builder; I'm familiar with my local zoning code and communicating with my local zoning and building departments about this project. I need to confirm feasibility and work up a cost estimate ASAP and the building department here has a really long response time for Q&A stuff right now. Hence this question!
The California Residential Code is derived from the International Residential Code and has a section on Concrete Masonry Construction, but I don't have the masonry-related background knowledge to understand a lot of it right now.
It looks like an architect or engineer's stamp may be required, but I know there are empirical standards both in that code and TMS 402 (which my library doesn't have, and it's pricey for an initial "can I do this?" investigation).
Furthermore, I get the impression that there are typical or best practice techniques for building walls from CMUs. I guess that's what I'm looking for, even if it isn't quite tailored to California code.
I believe what I'm wanting to build with would be ASTM-90 loadbearing CMUs.
Building Codes Illustrated looks promising; I'll see if I can get that or something similar from the library. The NCMA documentation is proving somewhat helpful too - lots of diagrams of best practices, etc. Thanks!
posted by sibilatorix at 4:28 PM on March 3, 2021 [1 favorite]
The California Residential Code is derived from the International Residential Code and has a section on Concrete Masonry Construction, but I don't have the masonry-related background knowledge to understand a lot of it right now.
It looks like an architect or engineer's stamp may be required, but I know there are empirical standards both in that code and TMS 402 (which my library doesn't have, and it's pricey for an initial "can I do this?" investigation).
Furthermore, I get the impression that there are typical or best practice techniques for building walls from CMUs. I guess that's what I'm looking for, even if it isn't quite tailored to California code.
I believe what I'm wanting to build with would be ASTM-90 loadbearing CMUs.
Building Codes Illustrated looks promising; I'll see if I can get that or something similar from the library. The NCMA documentation is proving somewhat helpful too - lots of diagrams of best practices, etc. Thanks!
posted by sibilatorix at 4:28 PM on March 3, 2021 [1 favorite]
What aramaic said. It's not enough to know how to put up a wall. Building codes have gotten tremendously complex and technical. This is why most people pay contractors/developers to build houses for them. But if you decide to try, good luck! Just be prepared to spend a vast amount of time and money.
posted by Artifice_Eternity at 4:28 PM on March 3, 2021
posted by Artifice_Eternity at 4:28 PM on March 3, 2021
It's a better question to ask your building department.
For our recent construction project our city building department was generally happy to answer "would you allow X?" questions but for "how do we comply with Y?" questions they pretty much always said "ask an architect or something, we're not here to advise you". I'm sure this varies from city to city, but generally their job isn't to teach you the rules, it's to verify that your plans and, later, execution comply with them.
posted by aubilenon at 4:52 PM on March 3, 2021 [2 favorites]
For our recent construction project our city building department was generally happy to answer "would you allow X?" questions but for "how do we comply with Y?" questions they pretty much always said "ask an architect or something, we're not here to advise you". I'm sure this varies from city to city, but generally their job isn't to teach you the rules, it's to verify that your plans and, later, execution comply with them.
posted by aubilenon at 4:52 PM on March 3, 2021 [2 favorites]
Upon seeing your reply, definitely check out the NCMA Details section for useful drawings of standard elements, and the Construction section. I mean, just about everything they have is handy in some way, but IMO those are probably the two most useful in terms of getting to grips with CMU fundamentals in a cost-free way.
...secondarily, and perhaps a bit offtopic, note that at least in my old area OSHA was starting to get pretty picky about silica exposure so if you plan on using powered cutting implements to divide CMU you should have a dust plan. Note that CMU shouldn't be installed when wet, which complicates dust control (a lot of folks seem to saw in advance, let them dry, and then proceed but I have no idea what NCMA/OSHA think about that myself). Of course, the old-school approach of hitting 'em with a tool works and is pretty dust-free.
...and when I say OSHA was starting to get "picky" I mean citing (the low-grade type of cite, not the Big Hammer) a steel fabricator for having a gravel yard in which the gravel may have had silica, reasoning that the trucks driving upon that gravel would kick up silica dust. I know this because the steel fabricator called me about it; the easiest solution was to spray the yard every so often. The longer term solution was to drive around a bunch, use detection gear, and establish that the dust did not break exposure limits within any reasonable timeframe. I mean, everyone has gravel yards, where else are you gonna put your laydown? In the shop?
Now, I see people cutting CMU unprotected semi-routinely, so you may not need to care -- but even so, personally, if I were gonna push my luck I'd cut the units somewhere out of sight and not near any civilians (last thing you need is a neighbor calling about your silica dust). This is mainly a "hey, watch out" type of thing -- just like hexchrome is for steel folks. Mainly gotta show you're paying attention and they'll usually leave you alone.
posted by aramaic at 4:58 PM on March 3, 2021 [3 favorites]
...secondarily, and perhaps a bit offtopic, note that at least in my old area OSHA was starting to get pretty picky about silica exposure so if you plan on using powered cutting implements to divide CMU you should have a dust plan. Note that CMU shouldn't be installed when wet, which complicates dust control (a lot of folks seem to saw in advance, let them dry, and then proceed but I have no idea what NCMA/OSHA think about that myself). Of course, the old-school approach of hitting 'em with a tool works and is pretty dust-free.
...and when I say OSHA was starting to get "picky" I mean citing (the low-grade type of cite, not the Big Hammer) a steel fabricator for having a gravel yard in which the gravel may have had silica, reasoning that the trucks driving upon that gravel would kick up silica dust. I know this because the steel fabricator called me about it; the easiest solution was to spray the yard every so often. The longer term solution was to drive around a bunch, use detection gear, and establish that the dust did not break exposure limits within any reasonable timeframe. I mean, everyone has gravel yards, where else are you gonna put your laydown? In the shop?
Now, I see people cutting CMU unprotected semi-routinely, so you may not need to care -- but even so, personally, if I were gonna push my luck I'd cut the units somewhere out of sight and not near any civilians (last thing you need is a neighbor calling about your silica dust). This is mainly a "hey, watch out" type of thing -- just like hexchrome is for steel folks. Mainly gotta show you're paying attention and they'll usually leave you alone.
posted by aramaic at 4:58 PM on March 3, 2021 [3 favorites]
IAAA, IANYA.
The profession, and the engineering profession, take a really dim view of "plan stamping", like you can loose your license for doing it.
So if you find out an architect or engineer is required, there's not much use spinning your wheels when these folks will know the rules cold, and won't stamp a set of drawings you bring in.
American Concrete Institute (ACI) 530 is code for unit masonry, you'll find it referenced somewhere in your IRC.
Sketches of plans and elevations to start would be OK.
posted by rudd135 at 7:13 PM on March 3, 2021 [2 favorites]
The profession, and the engineering profession, take a really dim view of "plan stamping", like you can loose your license for doing it.
So if you find out an architect or engineer is required, there's not much use spinning your wheels when these folks will know the rules cold, and won't stamp a set of drawings you bring in.
American Concrete Institute (ACI) 530 is code for unit masonry, you'll find it referenced somewhere in your IRC.
Sketches of plans and elevations to start would be OK.
posted by rudd135 at 7:13 PM on March 3, 2021 [2 favorites]
Looks like you need a professional, seeR606.1.1
posted by rudd135 at 7:18 PM on March 3, 2021 [1 favorite]
posted by rudd135 at 7:18 PM on March 3, 2021 [1 favorite]
This is not a DIY project for a novice. Hire a professional. In addition to the typical residential requirements from the International Building Code, I’d be shocked if CA doesn’t have an additional layer of seismic requirements.
posted by Kriesa at 7:35 PM on March 3, 2021
posted by Kriesa at 7:35 PM on March 3, 2021
Why are you anchored on CMU?
Are you aware of aerated block systems e.g. Hebel. High-strength, low weight - reduces labour a lot, able to be grout-filled, cut with hand tools. Many durable materials in market now. Give an architect some parameters and a budget, and say you want material options that fit ^ and are code-compliant.
posted by unearthed at 12:53 AM on March 4, 2021 [2 favorites]
Are you aware of aerated block systems e.g. Hebel. High-strength, low weight - reduces labour a lot, able to be grout-filled, cut with hand tools. Many durable materials in market now. Give an architect some parameters and a budget, and say you want material options that fit ^ and are code-compliant.
posted by unearthed at 12:53 AM on March 4, 2021 [2 favorites]
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posted by klausman at 3:33 PM on March 3, 2021