Block Rebar Questions

[65 Stang Project]

Just got my permits for a 24x24 garage. To my surprise, rebar is an option not a mandate in my area (eastern PA). That being said, I am going to run two pieces of 1/2" continuous rebar in the footer (concrete will include fiber). The footer has to be 36" below grade and will be 16" wide by 8" deep. I am going to have a few courses of 8" block to get 1 course above my slab. The question. I have a slopped lot, so my back block wall will be about 30" out of the ground. Meaning that their will be about a 30" difference between interior and exterior fill lines. How should I reinforce the back block wall so it does not cave out when I fill the inside and poor the slab? Should I fill all of the block cavities with concrete plus add vertical rebar? How far apart should the rebar be? Want to make sure that my concrete guy doesn't try to corners.

 

[brownbagg]

every four feet

 

[Dan in Pasadena]

Yes, grout the cells solid.

For residential purposes you will rarely regret having too much rebar but you may regret having too little. I'd use more vertical steel that four foot centers, but that's just me and I live in seismically active SoCal.

 

[cyamaha2007]

I would put rebar on 2ft centers. Then fill the cavity's solid. A block shop by me is still standing in perfect order after 80 years. I asked the owner how it held up so well he said his dad did rebar every hole and filled them with crete. He also soaked all the blocks in water for 24 hours before setting them.

 

[LutzTD]

I would put rebar on 2ft centers. Then fill the cavity's solid. A block shop by me is still standing in perfect order after 80 years. I asked the owner how it held up so well he said his dad did rebar every hole and filled them with crete. He also soaked all the blocks in water for 24 hours before setting them.

what does soaking the blocks in water do?

 

[NUTTSGT]

When I built the house garage, filled a bunch of block. I filled every so many feet and all the block in between the doors. I filled holes on both sides on the overhead door and walk in door. The corner blocks were filled along with a few more in the back wall. The extra ones were in front of were the cars sit. My thinking was incase somebody slipped (brake/gas) and hit the back wall it might keep the block from breaking.

 

[malibu101]

Sorry to go a little off topic...............
I see it's the OP's first post.

Welcome to GarageJournal, 65 Stang project!!
I live nearby in Walnutport. The world wide web can be a small world sometimes.

Lots of good info here to help with your build. Ask questions and look around!

 

[PittsS1]

I have the same situation- did vertical rebar 4' O.C. and a horizontal bond beam at the top with 2 #5s. Maybe some of the masonry folks can chime in with better info, but from all the people I've talked to and research I've done, just filling all the cores doesn't necessarily help all that much. I'm no expert though.

My house is 12" CMU, and had no core fills or reinforcement of any kind. It has 1 crack in an 8' basement wall. I did do a major renovation (lifted house off foundation) and added vert. rebar at 4' O.C. and a bond beam on top, but code required me to do that.

 

[cyamaha2007]

Yes he used tarps to make a pool and soaked the blocks overnight

 

[brownbagg]

what does soaking the blocks in water do?

fuk them up, please dont do that, one is against the building code and second it ruin the mortar joint, CMU block has to be completely dry

 

[brownbagg]

code is # 5 every four feet, three in the corner, one on each side of door or window, and two in the bond beam at top with corner bars.

 

[cyamaha2007]

wow im glad i didnt try that but construction practices have changed in 80 years i guess

 

[Bruce4310TX]

Dont waste your Money on fiber spend it on re-bar, Fiber only helps lessen the amount of surface tension cracks during the first 24 hrs after that its done its job. A good crete man and the proper mix you wont have a problem Its not a replacement for re-bar, Even wire mesh is better than fiber. Alot of contracters say with it you dont need re-bar thats False.

 

[65 Stang Project]

Thanks for all of the quick advice. I'm going to put rebar every 2' on the back wall, which has the most grade difference. The sides and front will have it every 4', more in the corners.

 

[1ownerT]

You may want to consider adding Durawall horizontal reinforcement to your block wall.

 

[NUTTSGT]

My house is 12" CMU, and had no core fills or reinforcement of any kind. It has 1 crack in an 8' basement wall. I did do a major renovation (lifted house off foundation) and added vert. rebar at 4' O.C. and a bond beam on top, but code required me to do that.

How high did you lift the house off the foundation ?

 

[wnstwolf]

Bruce beat me to it. Had a similar project as yours stang65. When the concrete trucks showed up and ralized they were pouring the footers they asked me why I ordered fiber reinforced mix. I had solid forms and tons of rebar overkill for my 46" wall that would also be acting as a retaining wall. AS I was doing it myself the truck driver laughed and said he had not seen bridges with that much rebar... but I did waste money on the fiber mix. Kept that for the slab though and no cracks...

 

[PittsS1]

How high did you lift the house off the foundation ?

Lifted it 36" temporarily in order to do the work. Added two courses of block and a double sill plate for an extra 19" of headroom. So when all the block was in place, trying to snake those 8.5' vertical rebars down in there with only 20" of space between the top of block and rim joist was a real treat.

 

[PittsS1]

For the O.P, this picture shows a cutaway of the bond beam around the top course. I had to leave a gap in here for lowering the house, hence the rebar being cut and a block or two missing, but normally this is continuous...

 

[ms fowler]

Do not soak the blocks. The mortar joint is made when the cement in the mortar is drawn into the dry block. Dry blocks make for stronger joints.

 

[NUTTSGT]

Lifted it 36" temporarily in order to do the work. Added two courses of block and a double sill plate for an extra 19" of headroom. So when all the block was in place, trying to snake those 8.5' vertical rebars down in there with only 20" of space between the top of block and rim joist was a real treat.

Thanks, 20" of clearance, I was wondering about that treat.