6 Inch Block Garage Foundation?????

fortstowe

Just received a call from a potential customer wishing to have a 24x32 detached garage foundation laid up with 6 inch block. Will 6 inch be suitable/structurally sound? I have never seen plans using 6's and typically use 8's. Any help would be greatly appreciated.

Glasshousebltr

You might have to ask a woman whether or not 6 inches is enough.

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Bob

stacker

it would depend on how good you used them

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Glasshousebltr

Yes indeed ....I concur .....it's all in how they're laid.

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Bob

concretemasonry

You can use normal 6" block for a garage foundation or for the entire garage if you wish.

I have seen 20 story load bearing apartment buildings built with 6" block with no steel or concrete columns. - 4 different strengths of block, normal mortar and some rebar and grout.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

K2

In my area block foundations are not allowed at all. I would stick to what is normal for your area unless there was an engineers stamp on the 6" foundation...

mdshunk

I've seen 6" interior partitions, but not so many bearing walls. I'm sorta wondering if they might even cost more at the block plant, versus the more typical 8"?

stacker

i just got some block today from the lumber yard.8in block cost me 1.83
the 6in i ordered cost me 1.47.
i layed a foundation about a month ago,90% of it was 8 in.the area around the garage was 6in block.i dont think you would lose that much load bearing power between the two.kinda like going from an 8 to a 10,you dont gain or lose that much.

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Dik Redi

Only difference is you need more reinforceing with 6" . Dura-wall evry other course, and instead of re-bar pined to footing evry 4' like the 8" are id pin it every 32" and grout,, even if its only 3 courses ( 2' ), if any taller why not throw a bom ( bond ) beam in there ,, cant hurt

concretemasonry

Dik -

That is a little much for reinforcement. Bad engineer, bad code or bad inspection. Almost any code will allow unreinforced block for garage foundation/stem wall. A bond beam makes sense since it gives you a chance to hold down the flimsy wood frame garage. From a practical standpoint reinforce and fill the cores where you have an anchor bolt.

A comparison with some good construction - They may have 32" or 48" reinforcement spacing for the lower one or two floors on a 20 story building. After that, it is less. Why go crazy on a garage?

Poor engineering is one of the reasons for the lack of masonry. Throw in an uneducated inspector in and you have a mess and less masonry.

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Tscarborough

Exactly, Concretemasonry. Combined with a total lack of knowledge of the difference between mortar and concrete, engineers tend to overbuild masonry structures, thus robbing them of their chief advantage: simplicity.

K2

Here block foundations are not done because of expansive soils. It's pretty tough to get even a poured concrete foundation to stay in one place on this kind of soil. Probably half the homes that are built around here are on stable soil and probably could be done in block. But, when an area is set up for poured walls, poured walls becomes the simple way.... I was a mason in another state in another life. I love poured concrete foundations and would never have anything else.

Subia29

??? If the engineer approved it. They should know calcs on load beariing. Right? If the mason contractor builds according to plans without challenging it & project fails,Who would be liable if it already passed inpection?Just a Question I need to know in the future.

concretemasonry

My point was that bad engineers and uneducated inspectors can lead to rediculous details and high costs, which decrease the amount of masonry used. I was not talking about liability since masonry codes have such an excessively high factor of safety and are proven to be much more reliable and adaptable to conditions than other building materials.

If California, they have some unique conditions and loads. I designed there. The engineers are quite good, but often have a high opinion of their abilities. Some feel the rest of the world should be built the same as the way they design for the worst conditions found in California. The fiasco with the blending of the UBC into the IBC is an example.

California does some great things in masonry in spite of trying to design for the world. I worked with local engineers when I was in Northridge after that quake and years later saw the great mason training they were doing at a high school near Fontana. - Cheerleaders at the masonry competition!!!

Some of the best masonry engineering I have seen was in South America. Often, the engineers work for the GC or developer and are a part of the job from beginning to end. This includes creating good, clear workable drawings and almost daily vists to the job (it may be 5 to 20 apartments 15 to 20 stories high).

These engineers are deeply involved and know their business. I asked one about what code they used and is answer was "WE USE YOUR CODE, BUT WE DO IT BETTER". Much of their knowledge goes back to the reinforced concretemasonry in San Diego in the late 1960's to 80's. They just took the modern engineering requirements, applied them to their conditions and made them workable and buildable. There would be more masonry in the U.S. if our engineers were more involved and knew more about masonry.

Dick

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Tscarborough

Let me give you an example of a job I was involved in that went to litigation. The engineer specified field testing of the mortar to a proportion specification, type S, and insisted that the mortar break at 1800PSI. To achieve this, the mason had to use such a stiff mix that the mortar cracked all over and leaked like a sieve.

Who was wrong? The mason did as specified, the engineer thought he was doing the right thing, per his normal concrete procedures and practices, and the owner got a crap building. Everyone involved lost money, just because the engineer did not understand mortar.

concretemasonry

The ASTM mortar spec (which I vote on) is one old inherited spec that engineers and architects do not read or understand.

You can specify what properties you want or you can specify what proportions you want used.

Both are good approaches, but a specifier cannot specify both.

To simplify - If you specify the performance (strength) you cannot control the proportions. If you specify the proportions, you have to accept the the strength you get.

Strength is not the criteria for mortar acceptabilty. Workability is the most important. The appendix to the specifications say that the specifier should specify the LOWEST mortar strength possible to carry the loads. Stronger is not always better. - You can make a 4500 psi block prism with 1900 psi mortar.

Dick

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Tscarborough

That is correct, and there is no test for field mixed mud.

fortstowe

Thanks to everyone that post an answer to my question. Here in Ohio, the price difference between 6's and 8's in about 10 cents. 96 for 6's and 108 for the 8's, so price is not a real big issue on such a small job. Concretemasonry you sure seem to know your stuff and really appreciate the information.

POOLMANinCT

now this a quality thread.
a field expert & engineer
w/o hidden agendas or motives discussing practice & theory....

ray

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lukachuki

Concretemasonry and Tsc make us all feel like mere mortals!


...for which we are all truly grateful!!! Their information and the good information of others on this board can be trusted but not always understood.

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