Concrete Concerns

[EddieWalker]

There are allot of block buildings done all over the world that don't have anything in the voids. Just block on top of block. Some have stood for decades, others have isssues. In my opinion, most of the issues are because of poor soil preperation and/or the wrong design in the foundation.

When you say that you added fiber to the concrete, does that mean you didn't use rebar? Did you have an engineer design your footings? What type of soil are you working in and what is the depth that you have to dig down to avoid frost heave?

In my experience, dealing with homes and problems with walls, cracking sheetrock and trim, it's always the foundation that is causing it. What you do with the walls is secondary to what was done with the foundation.

Why are you using block walls? It's aweful hard to beat the strength of wood framing. Block cracks, transfers outside temps and is notorious for leaking when it cracks. The only time I'd think that block walls would be a good idea would be for a basement, or a wall that will be below grade. Even then, just the parts that are below grade would be block with wood building up the rest of the wall.

If it's for secruity, your entry points and windows are what they will be going through regardless of what the walls are made out of.

If it's to cover the walls in rock, wood with 3/4 plywood sheething and lathe over it would be stronger.

With all the added drawbacks of finishing it off, running your utilities and insulating it, I think block construction would also be more expensive.

If it's a fire issue, stucco is very effective. Fine Homebuilding had a great article about a house that survived the Firestorms in Los Angales when every other house was burned down to the foundations. This house looked like it hadn't even been in a fire, except for the landscaping was all gone. The owner had 4 pane glass, no roof vents of any kind and had doubled the thickness of the stucco, along with a tile roof. Basically, he made it fire proof, and it worked!!

Eddie

 

[Dargo]

Not knowing where the OP is, I assumed that he is building somewhere like in the USVI some other similar area. If the buildings are not poured, then block with core fill is the main construction. When going around with a contractor who specializes in building basements in areas with high water tables or where the basement drops into a flood zone, I was surprised to find that the engineers call for block walls over poured in place concrete walls.

In a freaking sloppy muck pit, for lack of a better description, I helped him lay 12 courses of 12" block walls on a 24" wide by 24" deep foundation that had 4 #8 runs of rebar on stands to keep them in place while the 5000 psi concrete was poured. For those who don't know, #8 rebar is 1" thick. Believe me, it sucked to use a manual tube bender to make the 90 degree bends to go in the corners. The 12" block walls were laid on that foundation and every other core was filled to the top with 5000 psi concrete with a stick of #8 rebar in each of those cores as well. At the bottom of each of the non-filled cores a weep hole was drilled into the bottom of the outside and appropriate tile and pea gravel was used to carry the water to the sump pump. He also used a huge amount of perforated pipe snaked under the basement floor, also covered in pea gravel, that emptied into the sump as well. That basically carried all water trying to reach the outside of the wall, water that got into the wall and water that got under the floor into the sump pump. Of course heavy mastic was used on the outside of the wall and the sump pump had a double redundant double deep cycle marine battery backup setup so it would still operate for days without power.

To my surprise, the guy who lives there has never even painted the inside of his basement walls and has never even had a wet spot on his basement walls, let alone any leak. Other homes in his area with poured walls always fight dampness and weeping walls. Obviously I'm not a hydrologist or basement engineer, but I learned quite a bit from the one guy who paid a top engineer who specialized in that sort of work to design his basement. This same engineer designs 'hurricane proof' homes for the islands. Due to the lack of the ability to get quality concrete and the expense, he has designed several homes that have block walls with poured cores and the like.

 

[tommu56]

The better way to fill walls is do it in lifts less than 2 ft if you want all the cores filled.
Bond beams in u shapped block you lay rebar in you and fill with concrete. Most buildings I have seen with bond beams and filled cores cores were filled on 4' centers and had bar in them too along with bar in the bond beams.

tom

 

[CurlyDave]

I have never seen a concrete contractor use a stinger to settle the concrete fill in a block wall.

I always do, and on a 6' wall get 4-5" of settling compared to just pumping concrete in. Then you add enough concrete to completely fill the wall.

 

[Hooked_on_HP]

When you fill blocks with concrete you pour the concrete pretty wet. I is hard to get stiff concrete in that small of a hole. also you usually use a chip mix insted of using 3/4 stone. When you put a vibrator in wet concrete all the rock settles to the bottom. I would also worry about the mortar crumbling from the vibrator.

 

[Pops15]

If it's a fire issue, stucco is very effective. Fine Homebuilding had a great article about a house that survived the Firestorms in Los Angales when every other house was burned down to the foundations. This house looked like it hadn't even been in a fire, except for the landscaping was all gone. The owner had 4 pane glass, no roof vents of any kind and had doubled the thickness of the stucco, along with a tile roof. Basically, he made it fire proof, and it worked!!

Eddie

I didn't see the article but that sounds like a house I saw on the news. The firefighters only had the resources and time to save one house. They did a quick survey of the neighborhood and decided the stucco house was the most likely to survive the fire so they concentrated their efforts on it. The home owner was all smiles when he returned to find his home intact.....he said he didn't have homeowners insurance!

 

[CurlyDave]

When you put a vibrator in wet concrete all the rock settles to the bottom. I would also worry about the mortar crumbling from the vibrator.

I am not very worried about the aggregate sinking to the bottom or the mortar crumbling in the 30 seconds or so it takes to settle the concrete fill.

I agree these would be issues if I used the vibrator for several minutes.