pop top over unreinforced CMU wall

[DoubleStud]

I have a project where the existing house is a one story house with CMU walls built in 1947. We are adding another story. We just found out that the CMUs are running bond but all hollow. I am still not 100% sure how the 2x8 plate on top of cmu is attached. There is a chance maybe the all thread is embedded into the concrete footing and sticks out all the way to the top of the wall. I will find out more tomorrow when I do site visit. But from the sound of it, the plate is only attached to the wall occasionally at random spot. I will find out more about it tomorrow when i visit the site.

I need you guys opinion on this. Since we are adding another level on this wall (wood framing), I feel like I need to redo the sole plate on top of this wall. How would you go about it? I did not expect it to be be hollow, no bond beam, and no vertical reinforcement/grout every few feet. How would you reinforce this cmu wall and attach the 2x plate properly?

 

[ANE91]

In the US, I would not expect a house built in 1947 to have grout/reinforcement in the CMU. My market is like this.



Epoxy sleeves in the wall face work well.

Top-of-wall is a stickier wicket. Partial grout every 6’.

Of course, there are engineers in my market that don’t call out for any of this to be done. Contractors just stack on the second floor. Just waiting for that strong wind…

 

[XR250]

If you have access to the top of the wall, drop some full-height all-thread in the hole every 6 ft. ish and pour some runny grout in there.
Otherwise, stuff some rags in there and add anchor bolts.

 

[DoubleStud]

If you have access to the top of the wall, drop some full-height all-thread in the hole every 6 ft. ish and pour some runny grout in there.
Otherwise, stuff some rags in there and add anchor bolts.

So the all thread will act like a rebar? I was thinking about grout & rebar and cast in anchor. I guess a full ht all thread will simplify it.

 

[XR250]

So the all thread will act like a rebar? I was thinking about grout & rebar and cast in anchor. I guess a full ht all thread will simplify it.

It would but might be cheaper to use Rebar and anchor.
Rebar is also stronger than all-thread typically.

 

[TRAK.Structural]

May need to check the numbers at the end of braced wall lines to see if something more is required for any net uplift from lateral loading.

What is the size/condition of the footings under the CMU walls?

 

[DoubleStud]

looking at the footing from far away in crawlspace ( cant get close, if I try.. i may get stuck), concrete footing around 16-18” wide. For sure I will grout the corners and add rebars. What I dont really know how this wall is connected to the footing. If I add full rebar and grout, rebar wont be embedded to the footing. I will find out more today. Footing looks solid. House looks solid. Dont see any cracks/settlement.

May need to check the numbers at the end of braced wall lines to see if something more is required for any net uplift from lateral loading.

What is the size/condition of the footings under the CMU

 

[DoubleStud]

In the US, I would not expect a house built in 1947 to have grout/reinforcement in the CMU. My market is like this.



Epoxy sleeves in the wall face work well.

Top-of-wall is a stickier wicket. Partial grout every 6’.

Of course, there are engineers in my market that don’t call out for any of this to be done. Contractors just stack on the second floor. Just waiting for that strong wind…

Explain the epoxy sleeve on the face? How would that hold down the 2x plate?

 

[TRAK.Structural]

looking at the footing from far away in crawlspace ( cant get close, if I try.. i may get stuck), concrete footing around 16-18” wide. For sure I will grout the corners and add rebars. What I dont really know how this wall is connected to the footing. If I add full rebar and grout, rebar wont be embedded to the footing. I will find out more today. Footing looks solid. House looks solid. Dont see any cracks/settlement.

If there is no grout in the CMU wall currently than there probably isn't any real connection to the footing (that can resist uplift. You may have to grout enough area and use the weight of it to hold down any net uplift.

Unreinforced CMU can handle quite a bit of shear load, I would think you can get the numbers to work for that.

 

[DoubleStud]

If there is no grout in the CMU wall currently than there probably isn't any real connection to the footing (that can resist uplift. You may have to grout enough area and use the weight of it to hold down any net uplift.

Unreinforced CMU can handle quite a bit of shear load, I would think you can get the numbers to work for that.

I am thinking it may be grouted just the portion in soil where it retains 3 ft of soil. I will use a tape measure and see where my tape wont go any further. I will investigate what is going on with the existing all thread. It may help resist tension too if it is embedded.

 

[jerseyshore]

One thing that was a bit common around this time period (including my house that was built in the 60s) was they used a lintel-type block as the top course, not to really create a bond beam, but because the top of the block was 2 or 3" solid. They put the anchor bolts right into that and didn't have to grout any cells. And it's basically impossible to see that unless the top of the blocks are exposed.

A lot of times the older block walls need to be grouted just because they are old cinder blocks that are very porous.

If you are removing the existing roof for a new floor, why don't you just demo the top course and add a new bond beam? You can tie it into some vertical reinforcing all the way around and it makes it easy for new sill plate, anchor bolts, holdowns, etc.

 

[DoubleStud]

Update: We will add bond beam on the top of existing. It works out much better. The ceiling of the existing house was very low. So the plan was to "balloon" frame the wall down to below to raise the ceiling, and frame the second floor joists to a ledger. With the addition of the bond beam, we can just frame it regularly. Basically what jerseyshore was saying except we dont have to remove the top course.

 

[jerseyshore]

Update: We will add bond beam on the top of existing. It works out much better. The ceiling of the existing house was very low. So the plan was to "balloon" frame the wall down to below to raise the ceiling, and frame the second floor joists to a ledger. With the addition of the bond beam, we can just frame it regularly. Basically what jerseyshore was saying except we dont have to remove the top course.

Even easier then. They can use a knockout block or regular lintel block and drill holes for the vertical bars that you are adding into the existing wall. Only thing you have to check is holdown forces. Otherwise it's just like typical construction on a CMU foundation wall, which is always good when it comes to residential.