cinder block mortaring question


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Old 10-15-16, 09:48 PM
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cinder block mortaring question

Im building two cinder block posts between cement slab and portico to hold up, hold down and hold against lateral forces. Please dont tell me why I dont need to do this. That is not why Im here. I want to replace the existing metal supports, shown with something stronger, stronger then 4x4s or 8x8s. Something not just to hold up my portico, but to hold it down and hold it against lateral forces during a hurricane. The rest of the house has already been strengthened.

Ive done most of the repair and improvements to my 1954 home that Ive owned and resided in since 1986. However, Ive never mortared cinder blocks. I have in the last few months watched many videos on this and think that I can do it However, I do have a question.

Before mortaring the 1st block to the slab, Im thinking that I need to strip off all the old concrete paint and get down to the actual concrete. Do I or is there a way around this? I will be drilling a hole, using rebar, and filling the 1st few blocks with mortar after mortaring the joints as I stack the blocks.

I will not be using the blocks in the 1st 2 pics, but the ones in the last pic.

Any other advice?

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Old 10-16-16, 04:33 AM
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It would be best to remove the paint so the mortar can adhere better. I'd probably use a brick hammer to chip the paint off and rough up the concrete. Rebar drilled into the slab will also help. How thick is the slab where you intend to lay the block? You are adding more weight and may need a better footer. In that case you'd cut out that part of the slab so you can pour the footer.

Block won't necessarily tie the roof down any better than any other support. Whatever is used needs to be tied to the ground AND secured to the roof. With block you generally fill the block with concrete and install a hurricane tie down embedded in the concrete.
 
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Old 10-16-16, 05:19 AM
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You've already stated that you don't want to hear why not but cement blocks are great in compression but very weak in tension. So, just on their own your blocks will provide little uplift protection. If your goal is to provide lateral support and hold down for the roof then thin columns of CMU blocks is not a good solution.

How do you plan to attach your roof to the block? Just letting the roof rest on your columns will provide zero hold down protection. You will need some way to have steel connecting your roof all the way down to the footer with a continuous, strong load path in between.

How will you finish off the top of your block columns? You may need to box in above them to avoid creating a shelf that birds will love to nest on.
 
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Old 10-16-16, 06:02 AM
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one thread gets one title, duh...

ok im gunna back up and ask for suggestions here. What is the best way to do this? Hold portico up, down, and laterally? The slab is part of the original slab that supports the rest of the cinder block house built in 1954.

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Old 10-16-16, 06:36 AM
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IMO none of the blocks pictured are the right ones to use... the thing to do is to support the roof with 4" steel columns that provide the structural connection, then if you want cmu around it, use 8" C pilaster blocks, alternating the joints on each successive course, grouting the core as you go up.

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Old 10-16-16, 06:44 AM
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The main thing is for the support to be anchored to the ground and the roof structure!
Back when I lived in central fla I read an article that stated a correctly build wood structure was better able to withstand wind than a block structure. Wood can give a little in the wind and relies on ties to hold it together. Block will resist the wind until the force is great enough to blow it over.
 
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Old 10-16-16, 06:52 AM
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wanted to do that, but cant figure how to attach to slab so its strong laterally. The strongest simpson which would need to be inside the slab is rated for 800 pounds laterally at the base, with no rating higher up. I dont think that would provide much support laterally at 8 plus feet in the air. im confident that simpson ties top and bottom would give me the hold down that I need, but not the lateral.
 
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Old 10-16-16, 06:54 AM
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Lateral strength can be achieved by adding support near the top at a 45 angle.
 
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Old 10-16-16, 07:13 AM
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Steel columns would need to be fabricated with the proper flanges for attachment points. Any company with a structural engineer can do it.
 
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Old 10-16-16, 07:13 AM
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how many titles does a single thread really need?

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Old 10-16-16, 07:15 AM
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Yes, with an angle going the towards the house also for maximum strength. The 'triangle' can either be closed like the example or open - whatever you think will look best.
 
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Old 10-16-16, 07:17 AM
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"Any company with a structural engineer can do it."

that's what the city wanted me to do for my roof job too. Im not spending that kind of money.

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Old 10-16-16, 07:33 AM
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The structural engineer simply draws up the design, approves it, gives it to the welder. You can probably get a fly by the seat of your pants welder to do the same thing. The post just needs a flange around the bottom to anchor it down, probably a 4 hole flange, and the top of the post would have a similar flange, but also an added flange to fit in your inside corner where your x marks are in your first photo. The LENGTH of those flanges along with their attachment points is what provides your lateral resistance, so that no 45 degree angles are needed. Call a welding shop out to look at it. But what I'm saying is that if they don't have someone on staff that will take the liability of design (which is what structural engineers get paid to do) they might not want to take on the project.

There is not that much potential for lateral movement there in the first place.
 
 

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