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Homeowner Forum / Construction / April 2008strong concrete block walls
Hello, I will build a concrete block wall 4 blocks high for a garage. Three of the courses will be below grade. I want to make this wall as strong as practically possible. (I could not use a poured wall because of access problems). I live in a freeze/thaw area. I want to use some rebar in the cores for strength. Should these cores with rebar be filled with concrete or mortar? Also anything I can do to prevent cracking from the freeze/thaw cycles? Would a control joint on each wall make sense? Thanks, paul First of all lets start with the height. 3 blocks ie 24" down isn't deep enough for a freeze thaw area. > Hello, I will build a concrete block wall 4 blocks > high for a garage. Three of the courses will be [quoted text clipped - 7 lines] > a control joint on each wall make sense? Thanks, > paul > First of all lets start with the height. 3 blocks ie > 24" down isn't deep enough for a freeze thaw area. [quoted text clipped - 10 lines] > > a control joint on each wall make sense? Thanks, > > paul Not sure what you are trying to accomplish. What do you mean by "freeze thaw"? Obviously, you need to be below the frost depth in your area or no amount of rebar will save you. If you are concerned about lateral force, then core fill with concrete. A bond beam would help, though it's hard to see why it would be necessary on three courses. I assume you are filling the center and prepping for a slab---in that case the slab and fill would prevent the wall from pushing in. No need for control joints. The block will need a concrete footing below frost line wide enough to carry the dead and live loads imposed based on the bearing capacity of the soil. Vertical steel in concrete filled block cells at 4' on center and at each side of any openings should be adequate for your needs. A 16" wide by 8" deep footing with at least 2 #5 bars horizontal should be adequate for the footing.  Signature______________________________ Keep the whole world singing . . . . DanG (remove the sevens) dgriff237@7cox.net > Hello, I will build a concrete block wall 4 blocks high for a > garage. Three of the courses will be below grade. I want to [quoted text clipped - 5 lines] > freeze/thaw cycles? Would a control joint on each wall make > sense? Thanks, paul > Hello, I will build a concrete block wall 4 blocks high for a garage. > Three of the courses will be below grade. I want to make this wall as [quoted text clipped - 4 lines] > freeze/thaw cycles? Would a control joint on each wall make sense? > Thanks, paul Thanks. Basically I don't want the wall to crack. It will sit on a 8 x 16 footer at the frost line. The wall will be 4 blocks high with 3 below ground. My concern was could expansion/contraction from freezing/thawing crack the wall? And if so, is there anything I can do to prevent this? I'm not sure this would normally happen, so maybe it's not a problem, but since I don't know I sent the post. I will use the rebar in the footer and at 4' as DanG suggested. Thanks, Paul > > Hello, I will build a concrete block wall 4 blocks high for a garage. > > Three of the courses will be below grade. I want to make this wall as [quoted text clipped - 15 lines] > Thanks, > Paul What part of the country do you live in? On Apr 11, 2:16 pm, "PaulS" <semen...@ix.netcom.com> wrote: > "PaulS" <semen...@ix.netcom.com> wrote in message > [quoted text clipped - 21 lines] > Thanks, > Paul What part of the country do you live in? Midwest (Indiana) >> Hello, I will build a concrete block wall 4 blocks high for a garage. >> Three of the courses will be below grade. I want to make this wall as [quoted text clipped - 15 lines] >Thanks, >Paul How tall are the blocks? You probably will want the bottom of your footing about 4.5 to 5 ft down. > >> Hello, I will build a concrete block wall 4 blocks high for a garage. > >> Three of the courses will be below grade. I want to make this wall as [quoted text clipped - 18 lines] > How tall are the blocks? You probably will want the bottom of your > footing about 4.5 to 5 ft down. As long as the bottom of the footings are below code frost depth (which is certainly shallower than 4.5 to 5' in Indiana!) you should be fine. >> footing about 4.5 to 5 ft down. > [quoted text clipped - 3 lines] > Indiana!) you should > be fine. Former Hoosier. 36" should be good for that area. I wouldn't pour a footing for a doghouse without a couple #4 rebar's in it. > Former Hoosier. 36" should be good for that area. > > I wouldn't pour a footing for a doghouse without a > couple #4 rebar's in it. Well, that's pretty interesting considering who's saying it. You're an old timer and you often point out about the benefits of old time construction. They didn't use rebar in footings for generations, so what's happened to the soil recently that it's now required in every situation? Right, nothing. Code is an attempt to create a one-size-fits-all building. If a builder knows what they're doing, and take into account local conditions and compensates for them, there is no need for rebar. If Code calls for it, well, you have no choice and you have to put it in. That doesn't mean that the rebar actually adds any benefit and it does not compensate for poor foundation practices. R > On Apr 12, 10:52 am, "Glenn" <pilc...@kc.rr.com> > wrote: [quoted text clipped - 27 lines] > > R Most don't use rebar in driveways either but I want #4, 24" ew just because I like my driveway to stay together. Code around here calls for 2 #4 in footings, so just habit I suppose. Yeah, I go back to where we used 18" stone basement foundations directly on the ground with no footings. I'll take steel to stop the cracking they did. Cheapest thing for what they do in the whole building... > "PaulS" <semen...@ix.netcom.com> wrote in message > [quoted text clipped - 13 lines] > since I don't know I sent the post. I will use the rebar in the footer and > at 4' as DanG suggested. I just did a quick check on frost line depth in Indiana, and depending on where you are, it can vary from 30" to 42". The first thing you should do is verify the frost line design criteria. The buried portion of the foundation does not usually have a big problem with freeze/thaw. If you're garage is unheated and there's soil on both sides of the foundation, there's almost no chance of a problem. Freeze/thaw only becomes an issue if there is a fair amount of water in the soil. While you are excavating your foundation, you should determine what sort of soil you have and it's drainage capabilities. If there are any doubts, you can put in drainage tile (not actually tile, it's really pipe) around the perimeter, and/or use gravel and sand in the backfill. Rebar in footings is unnecessary unless you have doubts about your soil or if your subgrade preparations are faulty. A couple pieces of rebar won't make the footing act like a beam, it will just keep the pieces together, and, frankly, it's extremely rare for different sections of a footing/foundation to have any appreciable differential settlement unless the soil conditions and drainage are poor, or your subgrade preparations are faulty. I guess you catch my drift by this point. If you don't take into account the soil conditions, drainage and subgrade preparations, any work you do after that will be at risk. 'Superior' construction won't negate those failures. R The two #5 bars continuous proper laps and corner bars are code required minimum here. Perhaps the OP is not in a code compliance situation, but I would put it in as a minimum. Engineer designed would be higher. Signature______________________________ Keep the whole world singing . . . . DanG (remove the sevens) dgriff237@7cox.net >> "PaulS" <semen...@ix.netcom.com> wrote in message >> [quoted text clipped - 72 lines] > > R >The two #5 bars continuous proper laps and corner bars are code >required minimum here. Perhaps the OP is not in a code compliance >situation, but I would put it in as a minimum. Engineer designed >would be higher. I may have missed it but has anyone suggests a "permit" might be required for this job? In my area, I can go to the local city hall and ASK for the proper depths and construction practice that is acceptable. The inspector who will come out to look and see if your footings are in fact deep enough generally will give a homeowner guidance short ort of taking responsibility but will tell you what he expects to see in order to sigh off on the job. I cannot see where a permanent building like this would not require one. Pretty hard to hide it if you want to forgo a permit but if you want to do it w/o permit, you can still ask the "what if I wanted to do, such and such"? They would give some info better than the guessing game you are playing. The fellas giving you advice are going from experience and most likely know their job well but they won't be there to help you correct it if the local building inspector makes you do it. Big job, make sure you do it right the first time. Good Luck, Roscoe aka Rick Knowledge is like money, the less you talk about it the more people assume you have. |
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