Decks, Patios, Porches and Docks - Adding on to existing patio

Just curious what prep work I need to do to add on to an existing concrete patio. It's the normal 4-5 in thick concrete square that are on most new houses these days, only a little bigger. Just wondering if I need to put the expansion joints in between or what to do. Also, can I skim coat the existing concrete just so it looks uniform with the new? Plan on doing this sometime next month on leave. One of my many projects. Thanks!

Todd

Yes you'll be glad of the expansion joint next year after your new work has settled relative to the old.

Expansion joint - yes. Skim coat - no (it'll crack).

Would it be better to just bust up the old concrete so it all looks uniform? It's not too big of an area, but more so than the squares out your back door found on most new houses today. Probably about 3 of those total sq footage wise, but not an all day job to bust up. Just want it to look nice.

Not a bad idea. Otherwise your patio says, "Hi. I'm a blah expanse of concrete yet there's something noticeably odd about me." Sometimes success is in how unremarkable a thing is.

I know a skim coat would crack, but what about adding another inch or two in new concrete on top. Would that crack as well. Just curious cause if that will work, I will save myself some time and labor. If it won't, I'll just start busting away when it comes time.

Todd

What about adding new and then staining both as a means to achieve uniformity?

What you can imagine, is, the ground under your new concrete is going to sink a bit, no matter how pre-compacted. Let's say 1/8". Then the heavy new slab sure wants to drop 1/8". Can you hold it up along an edge? With a 1" flange of concrete? No, because the shear strength of concrete is very poor, it'll just crack there so the main part of the slab can settle.

Even an entirely new wide slab needs joints to guide where cracks happen, because it'll settle unevenly. Cracks may be inevitable, but we can dictate where they are.

The cracks may take a year or longer to appear.

If you want a uniform finish, maybe you could joint the new work in line with the old outlines, set it 1" higher, and also top the old with same mixture?

cool, thanks for the info. I'll be sure and update y'all when I get to doing it next month, if i can find the time in between everything else. I only have 18 days leave, and want to relax a little, lol. If not, I'll be home from Iraq in August for good.

Good planning and intentions.

I hope your neighbors have it done before you get back from doing you duty that is not fully appreciated. - Do you have their E-mail addresses that you can post?

Dick,

The powers that be in this forum aren't going to allow todrick to post his e-mail address, let alone those of his neighbors!!

todrick,

Pretty sure what Dick is looking for is a way to get them advise on the project. That's fine. Just PM Dick those e-mail addresses. (Click on Concretemasonry and send him a Private Message.)