Concrete vs. Cinder block

[banjopkr]

Hi,
I am planning a barn and I am going to do a second level that is backed into a hillside. I want to build a retaining wall that will also be a foundation for that end of the barn. The wall will be 32'x 10' with a 5' footing. I have been considering a both concrete and cinder block filled with concrete.
In running the numbers on cost cinder block is the most economical. I am not sure about the strength of block compared to concrete.
Anybody have any experience with this or comments.

 

[dooleysm]

As far as I know, they are both similar enough to not matter. We poured all our walls/footers because we had access to forms and knew how to use them. We didn't know how to lay block.

So, for us it boiled down to us having more time than money, and going with the cheapest option.

I like the look of cinderblock alot better than poured walls.

If your building is going to be insulated, I'd recommend using ICF's, like Reward Wall or other name brands.

 

[drm]

The concrete will be significantly stronger than block. The compressive strength of standard batch plant concrete is in the area of 4,000 psi. Standard block can be as low as 1,250 psi. Cinder block is even lower. Special block with provisions for reinforcing may be as high as 2,500 psi.

More important is providing the proper reinforcing for the walls. This includes dowels and reinforcing in the footing. 10 feet is on heck of a retaining wall. Have it designed by a professional engineer.

...Derek

 

[flusher]

IRRC, around here any retaining wall higher than 4 feet has to be engineered in order to get the building permit.

For a retaining wall 10' high, I'm guessing that you'll have to have some type of horizontal or angled pilings driven into the hillside to help stabilize the soil and keep the wall from eventually bulging.

 

[Matt_W]

It was my understanding that cinder block is more pourous than concrete. I have poured concrete walls for my full basement and have had no water problems.

 

[Birdhunter1]

Cinder block baseemnt walls are very prone to leaking water, properly poured and seaed concrete is not near as prone.

Cinder block contruction doesn't use rebar or wire mesh or anything, the mortar is mied on site and layed on site.
Have you ever dropped a cinder block off the top of a wall or shot it with a high powered rifle? Busts apart every time.

Ever do the same with a chuck of poured concrete? It don't bust most of the time.

 

[Farwell]

I have both concrete and cinder block walls. My cinder block walls weep water where my concrete walls do not. Both walls are coated with sealer on the soil side. Concrete is more expensive, requires forms and more reinforcement but over time I think that concrete is the better investment.
IMO
Farwell

 

[SPIKER]

actual retaining walls need to be checked out and made using dead man back into the hillside, someone mentioned this and that they should / NEED to be gone over by a real enginer5s even if there are NO codes in you're araea still need to have em built RIGHT the first time.

there is a 3rd option, there are concrete retainging blocks MADE for this use, and can be dry stacked quite high with propre back filling afterwards and the proper retension webbing back into the hillside they are a great option cheaper than poured but higher than block but also 100 times better.
they have to ne crane set is biggest pribkem

mark m

 

[CurlyDave]

A concrete wall will be much stronger.

A 10' retaining wall needs to be designed by an engineer, as others have said.

You may need to key this wall.

In order to build the wall you are going to need to excavate behind its final location. The excavation should be "benched" or stepped so that when you are backfilling, the fill rests on a level surface, it should not be placed into a wedge-shaped space.

Proper drainage behind the wall is important, both to prevent water seepage, and for strength. If the wall is drained, it only has to resist the force of the drain rock fill behind it, if it is not drained it must resist the force of the fill plus the force of the water.

In general, water exerts a higher force than the fill.

 

[bugstruck]

Needs to be engineered and properly drained as others have stated. Several ways for the engineer to attack it though. Over that 32' span in a foundation environment, I prefer solutions that take advantage of the cross walls first by spreading the loads to the ends and perhaps a center gut/shear wall if you can. Now if you can't get there that way (I think an engineer could), your into a true retaining wall design. 10' really is allot of dirt.

That wall can be engineered with block, but your still going to have enough concrete in the way of grout, cap beams, pilasters, and the like that you'd be better with all concrete IMO. With block you need rebar and horizontal joint reinforcement too, so the steel component is going to occur regardless of the other material decisions.

If the backfill was more in the <8' range, an all reinforced block solution would be rather more attractive, but still not necessarily preferred.

 

[banjopkr]

I have been speaking with an engineer and he said the wall if it is filled with concrete using the same amount of rebar and with horizontal beams every 2 feet it would be sufficeintly strong to do what I want. I am thinking block because after running the numbers a block wall with the same amount of concrete and rebar is about a 1000$ less than a formed concrete wall. This is due to the forms. I am looking at the block as a cheap way of forming the concrete and it seems pretty straight forward for a do it yourselfer from all I have read. Block is way cheaper than icf's.
The plan now is to drystack and surface bond a 32' by 8' room dived at 16' with a block wall if you were looking down at it it would be E shaped. I will be completly filling the wall facing the dirt with concrete and rebar. Footing size rebar spacing and total fill will be figured by an enginneer.
Thanks for all the replys by the way.
Chris

 

[Builder]

In 1984 I built a 10-12' high Ivany (sp.? )block wall with 5/8" rebar stickers in the footings, rebar from the footings to the top of the wall and then filled all the cells with concrete. I then veneered the face of the wall with fieldstone. I backfilled the wall with 3/4" gravel and perforated PVC standpipes that have outlets near the bottom of the wall. All the stone has fabric behind it and the pipes are sleeved in fabric.

It holds back an enormous bank with cars parked on top of it.

Not one crack or repair issue in 22 years. /forums/images/graemlins/smile.gif

I've installed both types of foundations and the poured concrete can crack as bad as concrete block, especially at or near corners. One nice thing about block is that if it bulges or cracks, you can repair it while concrete walls are nearly impossible to fix if they do crack. Whoever said concrete block can't be reinforced is mistaken.

It's all in the design or preparation work behind the walls and how well you reinforce your concrete or block.

 

[Builder]

In your 5' wide footing itself, place #6 bars at ~20" o/c perpendicular to the footing, then wire some #3 bar to them running lengthwise along the footing at 12" o/c forming a sort of "grid" in the footing. Next, take #8 bars and bend them at 90deg angles sticking up out of the center of the 5' wide footing at ~8" o/c. After your footing has dried and you start laying block make sure you lay Dur-O-wall every course or 16" o/c. You then slip your #8 bars down through your cells to the bottom of the walls at ~8" o/c.

I'd be happy to mail you a set of engineered plans of a 9&1/2' high wall to you if it'll help. It holds back 7' of fill and has a 6' wide base footing. I built this job and it was fine.

The nice thing about block, other than being cheaper, is you can do it yourself, with a minimal amount of tools versus hiring someone with forms (if that's important to you).

 

[bugstruck]

Sure enough. You can certainly do it with block. By quantity I've constructed more reinforced CMU walls than all concrete for retaining wall type situations. As you note, both have advantages and disadvantages. That standpipe solution you did was something I added to our jobs starting back in the early 80's when it was rare to see it. Typically I did gravel chimneys every 10' with a sliding U form against the wall while backfilling. Filter cloth too. Had a drain pipe in it of course. Then we ran a continuous gravel trench about a foot or so below the surface grade that capped the chimneys. All this was obviously connected to the drain tile. Worked great and saved loads of stone too. A full gravel backfill is great but that would have added about 1,000 tons of stone to just one
wall. They were quite long.

"It's all in the design or preparation work behind the walls and how well you reinforce your concrete or block." Absolutely.

 

[bugstruck]

Your on the right track given your needs and preferred methods. The Engineer is the important first step. The horizontal beams you mention make me think he is using the walls to pick up the load. The 5' foot size you mention sounds like an undersized retaining wall footer for that height? The Engineer could do a hybird solution or a single method. They typically prefer one primary method, my experience. Keep us posted on how he solves it. Always interesting to see how they attack it. Just stay away from the deadmen or grade beam tie back solution if possible. I've seen it and it can work well, but I'm not a fan of that for your situation, or most others except wood. You haven't mentioned it, so I assume it's not under consideration. Good Luck! Sounds like a very nice project.

 

[Builder]

I was going to suggest a 6' wide footing on a 10' wall.

Bugstruck I go nuts on this stuff. I always overdo it because I keep long term relationships with customers and there's nothing worse than going to a house or addition you built 5-10 years later and seeing a big crack in a wall.

 

[bugstruck]

Sounds familiar. I'll take my chances on the over-built side before I'll risk something marginal. Not worth it. I probably dropped about 20% more concrete by by volume into my projects than they needed, but those projects don't have even the minor cosmetic issues most eventually develop. Do it once, do it right and you never have to return for a warranty issue either. Funny how people will go bananas over quality issues with a car or consumer product, but the house, office building, etc. can be a time bomb and they'll accept that?? /forums/images/graemlins/shocked.gif I don't even try to figure that out. Yet when they get good work they genuinely appreciate it.

 

[keeney]

Here in MN when building 10' deep basements, it is quite common to use either block or poured concrete. Poured concrete would be 10" thick with rebar for 10' deep. Block for that depth would be 12" and core-filled and perhaps also have rebar. I think code here requires anything over 4' bare retaining wall or 8' foundation wall needs to be specifically engineered.

These walls are typically braced at the corners by the other walls of the basement and the floor deck at the top. They are not tied back into the slope.

 

[Irving Drinkwine]

Sorry I am a little slow, so please be patient.
Is what you are planning on building (The retaining wall part ) any different then a normal wall in a basement, and if so how?

Or if anyone could explain this to me I'd be grateful.

Also, the fabric that is used to cover the french drain pipes, is it a synthetic, non woven material? Could landscaping fabric be used instead?

I have a brick wall about 4 or 5 feet tall by 6 feet that someone built as a retaining wall. It is not yet back filled and there is nothing from the bricks to tie the wall into the earth behind it. Can I add something?
Any suggestions for an easy fix?
Not filled in, I mean not intentionally filled. The dirt behind he wall has collapsed some and while I could get back there, it is probably 2 feet above the base of the wall.


\ |
\ |
\|
|
TTTTTTTTTTTTTTTT
\=slope of soil
|=brick wall
TTTTT= ground level on other side of retaining wall.

Not to scale and very crude, but hopefully something to make my written description a little clearer.

Construction of any type is an area where I'm not very knowledgeable, so any help or advice would be appreciated.

__ID-->

 

[Ryan03]

I grew up in a house with a block basement, the home my wife and I built and now live in has a poured concrete basement. I think the biggest problem with poured basements is when the contractor or batch plant tries to cut corners on unsuspecting home owners. I was very fortunate that my wife is a Civil Engineer with a P.E. license. She caught our contactor trying to just but the rebar together in the bottom corners of a couple forms, rather than overlapping and tying it together. Needless to say, she made them fix it, and at that time also informed them that she took Friday off,[the day they were pouring] and would be there bright and early with her slump cone and a half dozen test cylinders[ the company she used to work for specialized in materials testing and had a full in house lab.] Everthing ended up testing just fine, and the remaining cylinders broke well above 4,000 psi in the 28 day test. Now 4 1/2 years later our basement is trouble free and dry as a bone, with one minor crack in the wall near our walk out area. I attribute this to it being done right. As far as a couple others that this sub did, lets just say they were not as fortunate as us and have had problems, as for the sub, they are no longer in business. Poured walls can be fixed, as we do it all the time at work with bridge head walls and such, but make no mistake that it is a major pita. compared to a block repair, and the lonegivity of it as compared to a block wall repair is a debatable subject, especialy in my part of the country where we get several freeze thaw cycles. IMO, either style, block or poured, are only as good as the people building them. One other drawback that comes to mind is how much colder a poured basement is than a block basement, even with the foam insulation on the outside of the walls. It takes a couple of weeks with the heat on to get the walls warmed up [Have'nt got around to finishing the basement yet].