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I want to pour additional concrete to extend my back patio by 12 feet.
The edge I am going to pour against (on the existing patio) is highly irregular and is not a square face.
I know you have to have an expansion joint, but other than renting a concrete saw and squaring up the face, how could I pour this concrete without having issues later ?
How irregular is the surface?

I'd put down a form board against the surface, pour the slab and after it cures completely, fill the gap with a vinyl "crack" sealer. If you're talking several inches of gap, you may just want to fill in the area with decorative pea gravel.
(07-25-2018, 12:18 AM)Catch Wrote: [ -> ]How irregular is the surface?

I'd put down a form board against the surface, pour the slab and after it cures completely, fill the gap with a vinyl "crack" sealer. If you're talking several inches of gap, you may just want to fill in the area with decorative pea gravel.

Catch, when they poured the patio slab, they used two 1"x 4" inch stacked as the retainer boards for the pour. The bottom board bowed out under the weight and was about 2" out in the center.
(07-25-2018, 12:24 AM)Grendelmort Wrote: [ -> ]
(07-25-2018, 12:18 AM)Catch Wrote: [ -> ]How irregular is the surface?

I'd put down a form board against the surface, pour the slab and after it cures completely, fill the gap with a vinyl "crack" sealer. If you're talking several inches of gap, you may just want to fill in the area with decorative pea gravel.

Catch, when they poured the patio slab, they used two 1"x 4" inch stacked as the retainer boards for the pour. The bottom board bowed out under the weight and was about 2" out in the center.

Will the seam be in a traffic area or basically up against a wall or other structure?

To fill a gap that wide, you can still use vinyl sealer, but you would want to stuff some PVC foam pipe insulation into the crack first. That will take up a lot of the area of course so that the sealer isn't too thick and prone to cracking or separating.

You can find the foam pipe insulation at Home Depot, usually used to protect hot water lines. I'm guessing your slab will be about 8" thick? You could either fill it halfway up with pea gravel, then foam, then caulk, or just stack multiple tubes on top of each other. Leave about 1" depth for the caulk.

Good luck :)

Guest

They sell something in the big box stores that you can paint on the existing concrete to make it adhere to the new concrete, however, if you are putting an expansion joint I'm not sure you need this. But you can literally ask those guys at the store and they'll know.

Another trick, get estimates from contractors for extending the patio and ask them how they plan to solve that problem. It's a little sneaky but you may end up hiring them to do it anyway.
(07-25-2018, 12:31 AM)Catch Wrote: [ -> ]
(07-25-2018, 12:24 AM)Grendelmort Wrote: [ -> ]
(07-25-2018, 12:18 AM)Catch Wrote: [ -> ]How irregular is the surface?

I'd put down a form board against the surface, pour the slab and after it cures completely, fill the gap with a vinyl "crack" sealer. If you're talking several inches of gap, you may just want to fill in the area with decorative pea gravel.

Catch, when they poured the patio slab, they used two 1"x 4" inch stacked as the retainer boards for the pour. The bottom board bowed out under the weight and was about 2" out in the center.

Will the seam be in a traffic area or basically up against a wall or other structure?

To fill a gap that wide, you can still use vinyl sealer, but you would want to stuff some PVC foam pipe insulation into the crack first. That will take up a lot of the area of course so that the sealer isn't too thick and prone to cracking or separating.

You can find the foam pipe insulation at Home Depot, usually used to protect hot water lines. I'm guessing your slab will be about 8" thick? You could either fill it halfway up with pea gravel, then foam, then caulk, or just stack multiple tubes on top of each other. Leave about 1" depth for the caulk.

Good luck :)

Thanks man, I think I know what you are getting at.
Would it be possible to square up the face with Hydraulic Cement and then go from there using the standard 1/2" expansion joint ?
(07-25-2018, 12:39 AM)Grendelmort Wrote: [ -> ]
(07-25-2018, 12:31 AM)Catch Wrote: [ -> ]
(07-25-2018, 12:24 AM)Grendelmort Wrote: [ -> ]Catch, when they poured the patio slab, they used two 1"x 4" inch stacked as the retainer boards for the pour. The bottom board bowed out under the weight and was about 2" out in the center.

Will the seam be in a traffic area or basically up against a wall or other structure?

To fill a gap that wide, you can still use vinyl sealer, but you would want to stuff some PVC foam pipe insulation into the crack first. That will take up a lot of the area of course so that the sealer isn't too thick and prone to cracking or separating.

You can find the foam pipe insulation at Home Depot, usually used to protect hot water lines. I'm guessing your slab will be about 8" thick? You could either fill it halfway up with pea gravel, then foam, then caulk, or just stack multiple tubes on top of each other. Leave about 1" depth for the caulk.

Good luck :)

Thanks man, I think I know what you are getting at.
Would it be possible to square up the face with Hydraulic Cement and then go from there using the standard 1/2" expansion joint ?

Sorry, I respond with a question every time you ask a question Chuckle

What part of the Country are you in? Do you see regular freeze/thaw cycles? Honestly, I am not real familiar with Hydraulic Cement, but I'm assuming it's similar to grout? When I was in construction, we'd often grout the finished structure to give it a cleaner, smoother finish. But grout would pop off in time due to thermal expansion. Granted, in your case, it would be up against the expansion joint and would be readily seen anyway.

If you're in the northern half of the Country, I don't think any surface coating would be a good idea. Also, it sounds like your "patch" could be up to 2" thick towards the top and bottom, almost 0" at the center. You'll get a slightly different expansion in the thicker area of the patch of course...not good for adhesion. But, I've been out of the industry for quite awhile and am not sure what new "super products" they have come up with since then.

Do you have a local ready mix plant you could ask what they recommend? I wouldn't ask the guys at Home Depot/Lowes/etc, though they are often great people, they aren't typically experienced contractors.
(07-25-2018, 12:48 AM)Catch Wrote: [ -> ]
(07-25-2018, 12:39 AM)Grendelmort Wrote: [ -> ]
(07-25-2018, 12:31 AM)Catch Wrote: [ -> ]Will the seam be in a traffic area or basically up against a wall or other structure?

To fill a gap that wide, you can still use vinyl sealer, but you would want to stuff some PVC foam pipe insulation into the crack first. That will take up a lot of the area of course so that the sealer isn't too thick and prone to cracking or separating.

You can find the foam pipe insulation at Home Depot, usually used to protect hot water lines. I'm guessing your slab will be about 8" thick? You could either fill it halfway up with pea gravel, then foam, then caulk, or just stack multiple tubes on top of each other. Leave about 1" depth for the caulk.

Good luck :)

Thanks man, I think I know what you are getting at.
Would it be possible to square up the face with Hydraulic Cement and then go from there using the standard 1/2" expansion joint ?

Sorry, I respond with a question every time you ask a question  Chuckle

What part of the Country are you in? Do you see regular freeze/thaw cycles? Honestly, I am not real familiar with Hydraulic Cement, but I'm assuming it's similar to grout? When I was in construction, we'd often grout the finished structure to give it a cleaner, smoother finish. But grout would pop off in time due to thermal expansion. Granted, in your case, it would be up against the expansion joint and would be readily seen anyway.

If you're in the northern half of the Country, I don't think any surface coating would be a good idea. Also, it sounds like your "patch" could be up to 2" thick towards the top and bottom, almost 0" at the center. You'll get a slightly different expansion in the thicker area of the patch of course...not good for adhesion. But, I've been out of the industry for quite awhile and am not sure what new "super products" they have come up with since then.

Do you have a local ready mix plant you could ask what they recommend? I wouldn't ask the guys at Home Depot/Lowes/etc, though they are often great people, they aren't typically experienced contractors.

Catch, you really know concrete.
(07-25-2018, 12:56 AM)phxsparks Wrote: [ -> ]Catch, you really know concrete.

I used to Chuckle

I've never poured a driveway, sidewalk or even a patio in my life. This is more what I used to do:

[Image: Kk0FqhH.jpg]

The tallest structure we built was 380' (shown in the photo). We used a method called "slip form"...continuous, non-stop pouring of concrete, 'round the clock. Once you started and the forms started moving up, there was no longer the option to stop.

@Grendelmort , I had one other thought. I still had my CAD program open from today, so I made a quick sketch (a picture is worth a thousand words lol). Since you do have a fairly wide gap, you could possibly stagger your expansion joint so that it's a more common type of seam, but still allows for the bulged area. Another cool thing is this would "key" the two slabs together essentially.

Here is the thought:

[Image: oVTIOaI.png]

But I still think the best idea is call your local ready mix plant and see what they suggest.

Good luck and enjoy the patio when you're done Drinks
Make a form to square up the irregular joining face. Pour n cure. Make proper joint for the new expansion off the true-up.
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