Concrete / ratwall question

[Need more space]

After spending sometime on this forum I've decided to do a garage addition, you guys are spending my money for me lol...

The plans are to do a 16 foot addition off the back of my 16x24, the city gave the permit and required a 2 foot ratwall. My plans are to do a 1 foot wide and 2 foot deep ratwall on all four sides. Im going to pour ratwall first and then prep the middle and pour the floor on top. I'm in michigan to give you idea of weather conditions.

Questions

1. Since I'm pouring new cement aginst old concrete should I put anything between the two? Or just between the floors or between floors and ratwall

2. Since I'm pouring in two pours should I put some rebar in the wet ratwall so it anchors to the floor when I pour that on top?

3. What have you had best luck with for prepping the ground between the ratwall to properly support the new floor? Was think slag or or gravel?

4. If I use rebar and pour a 6 inch pad do you think I can pour and not use joints or saw cut for a nice smooth floor?


Thanks guys!!!

 

[blazentrout]

We have always pored them in one shot and when the were working up an existing foundation it was only the 3 outside walls that got the rat wall. we also just butted up the new pour to the old with dowels/rebare epoxied in place to tie everything together.
1. no
2. yes
3. sand or road base with a vapor barrior.
4.its a 50/50 on what it will do. may luck out and it does not crack but why not just fill the control joints with caulk and not have an issue.

 

[Rookie2]

whatz a ratwall ?

 

[Kevin54]

Welcome to Garage Journal. You have quite a few fellow members up your way.

In doing a rat wall at 2' deep, then going back and pouring your floor on top, why don't you prep everything all at once, and do everything in one pour, both the rat wall and floor. Either way, you are basically going to have a monolithic slab. I think it would save you time and money to do it all at once. You can go ahead and have your rebar already in place. I also think that you should pin the old floor to the new floor. That is nothing more than drilling 1/2" holes horizontally into the old floor at certain intervals, and driving in, or a lot of people will epoxy in lengths of rebar. This will keep one floor from dropping away from the other floor.

But just from a personal standpoint, I'd certainly go at it all at once and be done with it.


ROOKIE.....A rat wall is just what it states.....It's a rodent barrier.

 

[JoeFin]

Im going to pour ratwall first and then prep the middle and pour the floor on top.

Uses about 20% less concrete doing a "Non-monolithic" pour. Just leave the Rat Wall good and rough or form a shear-key in it with a 2"x4" when you pour it

I was in the same boat of needing more space and added 15'x24' on to my garage as well. And yes out here we call them "Stem-walls" but I drilled the foundation, epoxied in several pieces of rebar, and then tied the new rebar on to that.

Here we have to overlap the rebar tie 24". We also have to make sure the existing foundation is reasonably cleaned off. I also used a concrete bonding agent just before the pour

 

[mtmgtz]

The ratwall must be a Michigan thing. Never heard of one here in Illinois. I googled it and most references were to Michigan. You guys got a bad rat problem up there?

 

[Need more space]

We have always pored them in one shot and when the were working up an existing foundation it was only the 3 outside walls that got the rat wall. we also just butted up the new pour to the old with dowels/rebare epoxied in place to tie everything together.
1. no
2. yes
3. sand or road base with a vapor barrior.
4.its a 50/50 on what it will do. may luck out and it does not crack but why not just fill the control joints with caulk and not have an issue.

The reason I was thinking four sides of rat wall was just added support for pad, and the reason im having a issue doing in on pour was prepping middle. There used to be a old shed on cinder block that I'm removing. I wasn't sure I could get the area compacted well without the rat walls holding the center in place. Planned on digging center out and backfilling with a good base.

 

[C96]

I think your proposed way is just fine, seen it done this way many times. May take you more time and effort, but agree with your thought on the compaction issue.

Good Luck

 

[yeldogt]

Learn something every day .. never heard of a rat wall

 

[Rubrsidedown]

Rat wall.... Frost wall... same thing no?

 

[Need more space]

Welcome to Garage Journal. You have quite a few fellow members up your way.

In doing a rat wall at 2' deep, then going back and pouring your floor on top, why don't you prep everything all at once, and do everything in one pour, both the rat wall and floor. Either way, you are basically going to have a monolithic slab. I think it would save you time and money to do it all at once. You can go ahead and have your rebar already in place. I also think that you should pin the old floor to the new floor. That is nothing more than drilling 1/2" holes horizontally into the old floor at certain intervals, and driving in, or a lot of people will epoxy in lengths of rebar. This will keep one floor from dropping away from the other floor.

But just from a personal standpoint, I'd certainly go at it all at once and be done with it.


ROOKIE.....A rat wall is just what it states.....It's a rodent barrier.

Thanks for the welcome! Would love to,do it in one pour however concerned i won't be able to get it compacted well with the rat wall dugout. I like the rebar idea, ill be doing that!

 

[Need more space]

Uses about 20% less concrete doing a "Non-monolithic" pour. Just leave the Rat Wall good and rough or form a shear-key in it with a 2"x4" when you pour it

I was in the same boat of needing more space and added 15'x24' on to my garage as well. And yes out here we call them "Stem-walls" but I drilled the foundation, epoxied in several pieces of rebar, and then tied the new rebar on to that.

Here we have to overlap the rebar tie 24". We also have to make sure the existing foundation is reasonably cleaned off. I also used a concrete bonding agent just before the pour

I like the sound of the bonding agent, I'm choosing to,use rebar however inspector said it was up to me.

 

[Need more space]

The ratwall must be a Michigan thing. Never heard of one here in Illinois. I googled it and most references were to Michigan. You guys got a bad rat problem up there?

I've lived in the same city for 20years, never seen any however some of the surrounding areas have them bad

Rat wall.... Frost wall... same thing no?

Not to sure, but seems to be the same idea

I think your proposed way is just fine, seen it done this way many times. May take you more time and effort, but agree with your thought on the compaction issue.

Good Luck

Thanks, I'm unsure of stuff I've never done. I tend to over think things!

 

[blazentrout]

The ratwall must be a Michigan thing. Never heard of one here in Illinois. I googled it and most references were to Michigan. You guys got a bad rat problem up there?

Not were i live but we seem to have big issue with the 2 legged ones over in Detroit.

 

[wssix99]

The ratwall must be a Michigan thing. Never heard of one here in Illinois. I googled it and most references were to Michigan. You guys got a bad rat problem up there?

Where I live in IL, the rats are 30-40 lbs. and can't get through tiny openings. Maybe MI rats are more like mice?

 

[Need more space]

Not were i live but we seem to have big issue with the 2 legged ones over in Detroit.

Lol, your so right. My job put me in the city often

 

[mtmgtz]

Where I live in IL, the rats are 30-40 lbs. and can't get through tiny openings. Maybe MI rats are more like mice?

Lol. I live in central IL and did live in Southern IL. Rats aren't really an issue around these parts. You might run into a few rats under the aeration floor (above concrete grade) of a grain bin. Nice food source for them.

We have a few of the two legged variety as well but they were elected in...

Not sure that a rat wall and a frost wall would really be the same. A rat wall may not go below the frost line. Frost walls are generally a footing/foundation so therefore structural. A rat wall sounds like nothing but a vermin barrier.

 

[Need more space]

Lol. I live in central IL and did live in Southern IL. Rats aren't really an issue around these parts. You might run into a few rats under the aeration floor (above concrete grade) of a grain bin. Nice food source for them.

We have a few of the two legged variety as well but they were elected in...

Not sure that a rat wall and a frost wall would really be the same. A rat wall may not go below the frost line. Frost walls are generally a footing/foundation so therefore structural. A rat wall sounds like nothing but a vermin barrier.

Was hoping my rat wall also served as structure, thought it would since it was 2 feet down and a foot wide for the whole perimeter of the new pad.

 

[wssix99]

Was hoping my rat wall also served as structure, thought it would since it was 2 feet down and a foot wide for the whole perimeter of the new pad.

Have you dug down to see what the existing foundations are like?

 

[mtmgtz]

Was hoping my rat wall also served as structure, thought it would since it was 2 feet down and a foot wide for the whole perimeter of the new pad.

2 feet down is not going to get below the frost line in Michigan so it's not going to be structural in the sense of a foundation wall/footer.

Why are you making it 12" thick? That is really thick for a vermin barrier. I'm not sure how your existing garage is constructed, but I would forget the 12" by 24" deep rat wall and just pour a 6 or 8" foundation wall with footer below the frost line (not sure what Michigan is). It should still meet the rat wall requirements.

I also would not dowel in the 24" rat wall into your floor slab (if you still went that path). You're asking for lots of cracks since 24" deep isn't going to prevent frost intrusion. Your slab will heave from frost differently than the rat wall. You don't really want to tie the two together in any case, other than a monolithic slab (that's a single pour though) but those don't usually go down 24" and they use insulation to prevent frost intrusion.

 

[Need more space]

Have you dug down to see what the existing foundations are like?

No plan to this weekend

 

[Need more space]

2 feet down is not going to get below the frost line in Michigan so it's not going to be structural in the sense of a foundation wall/footer.

Why are you making it 12" thick? That is really thick for a vermin barrier. I'm not sure how your existing garage is constructed, but I would forget the 12" by 24" deep rat wall and just pour a 6 or 8" foundation wall with footer below the frost line (not sure what Michigan is). It should still meet the rat wall requirements.

I also would not dowel in the 24" rat wall into your floor slab (if you still went that path). You're asking for lots of cracks since 24" deep isn't going to prevent frost intrusion. Your slab will heave from frost differently than the rat wall. You don't really want to tie the two together in any case, other than a monolithic slab (that's a single pour though) but those don't usually go down 24" and they use insulation to prevent frost intrusion.

I was going 12inches thick with hope that more is better... Maybe I'm way off