Concrete Block Orientation

[Intheswamp]

I have noticed that several coop building projects have the foundation piers constructed with hollow concrete blocks turned sideways. These types of blocks are designed to be used with the openings vertical and filled with concrete. For a small chicken coop they should be fine without being filled but the correct orientation I would think should still be maintained.

With the hollow blocks laying on their sides (openings visible) there is probably a little over 40 square inches of concrete support per stack of blocks. With the blocks vertically oriented there is probably more than 60 square inches of concrete support per stack of blocks. A block oriented vertically has shear stability all around it's perimeter (can't sway more one way or the other) but with a block laying on it's side it only has stability down two sides...it can sway(and break) in the direction of the other sides.

Laying the blocks vertically will require either a cement pad to rest them on or possibly a thinner "cap" block to rest them on to keep them from sinking into the ground....at the top of the block a piece of pressure treated 2x8 would work good to go between the blocks and beams...slide a piece of roofing felt or piece of tin flashing in between the cement and wood for some added termite protection.

Another point is that the hollow concrete block is stronger in the vertical position than it is in the horizontal.

Of course, if you can acquire solid concrete blocks then it's a non-issue.

I'm no building contractor so I may be a bit off on my figuring but this has been on my mind and I thought I'd mention it...
Best wishes,
Ed

 

[naturababe]

thanks for the tip, i'm thinking of putting my coop up on concrete blocks to help prevent rot.

 

[CityChook]

Makes sense to me. We put our blocks on a cement pad, in a single layer, and we filled them with sand to give them more stability. The coop is unbelievably heavy, so I wouldn't have wanted to try it with the blocks laid horizontally.

 

[patandchickens]

That is an interesting point, but I think I'm going to take the opposing view on this one.

In the case of a typical chicken coop, I do not think there is a lot of danger in overstressing the concrete (even in a sideways block) -- the main and commonest problem is the block sinking into the ground. It will tend to do that no matter WHAT you do, especially on clayey and/or frosty soils, but the more you can prevent it, the better.

If you have a block "the right way", with the cavities vertical and the thin wall ends bearing on the ground, there is significantly more psi pushing the block into the ground than if you have it "sideways" with its totally-solid side on the ground.

I suppose the ideal situation might hypothetically be to orient it "the right way" but atop a paver just a bit larger than the concrete block.

But as I say, I am just skeptical that a normal coop is going to be applying so much pressure to a "sideways" block as to cause the concrete to fail, so it seems to me that "sideways" may actually be a perfectly valid orientation.

Also not a contractor or structural engineer <g>,

Pat

 

[Intheswamp]

Howdy Pat. Yelp, I think I stated in the first post that you've gotta have something solid for the vertical block to rest on. I think an ideal situation would be to dig down below the frostline and pour a concrete pier footer and then block up from there. I definitely agree that we shouldn't stand the blocks up vertically on bare ground...would not be a good thing.

I don't think the static weight of the smaller coops would put enough pressure on the sideways blocks to make them collapse either, but I can imagine instances where a sideways force could cause the sideways blocks to collapse. Accidentally bumping the coop with a trailer or tractor while working around it could push the coop in a direction that could cause a sideways block to collapse where the vertically oriented block would probably hold. Even strong winds could do it...I've seen 75' pecan trees with their tops bent over touching the ground (Hurricane Opal and the next morning the trees were laying on the ground among other things

). Even strong thunderstorms can generate some awesome winds. These are some extreme situations, I know, that hardly anyone will experience but they are possible.

I guess what I was trying to say with my post is that the engineers designed the blocks to be used in a specific way so why not take advantage of their knowledge and design skills? It wouldn't take too much more effort to turn them vertically with a small added expense for cap blocks or maybe footers and you wouldn't have to worry about shear forces collapsing the structure as easily. But, it probably is over engineering for a chicken coop...at least until Orca the Mighty Orp jumps down from the roost one day and knocks the whole coop down.

Best wishes,
Ed

 

[gryeyes]

Oh, great, y'all have made me go outside to LOOK at the concrete blocks under the coop and duck house I've built.

Whew! Guess I'm not as dumb as I almost thought I was!

I've taken so many little "Linda Shortcuts" in the construction of my coops, I didn't trust that I'd oriented the concrete blocks correctly.

'Course, they're not on pavers, so the brand new coop will probably sink into the clay soil next rainy season. (I even waited UNTIL after some significant rain to dig in that ground, because it's so hard the rest of the year I would never have been able to level the blocks.)

 

[Intheswamp]

Quote:
Well...if you're concerned about it you could get a scissor-jack or bottle jack and slip under the beams beside each block and jack it up and slip a cap block under the bottom block...carefully.

Ed

 

[Penturner]

The difference in the strength of the block when on it's side in comparison to when it is upright is extreme. The blocks are "Engineered for maximum strength from minimal material and orientation is a major factor in how they get that. I would not want anything I built standing on the side of a block. As for issues of sinking. that is one more thing that needs to be adequately done in order to build an effective foundation. A solid level surface is needed for the blocks to rest on. even if it is just a shallow trench of gravel or sand. a piece of lumber, pavers, or even a 3 or 4 inch thick slab of concrete. In my experience I build the foundation as exact as I am capable of because every piece added to the structure after that adds it own little bit of imperfection. by the time you get to the roof. all of these add up to some pretty unsightly mistakes.
Just to give you an idea. I can break a block in half by kicking it on the side. I would probably need a sledge hammer to break it from the top to the bottom. at least a break that ran completely through it. Really big difference.