Results 1 to 4 of 4

Thread: Seeking Advice on Construction of Concrete Patio

  1. #1

    Seeking Advice on Construction of Concrete Patio

    My wife and I would like to put a concrete patio in the no-man's land between the house and the garage. Currently it is a mass of pathetic looking grass and dirt.

    A description of the pad we'd like to pour and the area it will be poured in. It will be 14 ft. wide by 12 ft. long, and from the reading I've done, 4 inches thick. On two sides it will be bounded by a concrete sidewalk leading to the back door of the house and on the other, the concrete block foundation of the garage.

    Do I need to form the sides that will abut the sidewalk and garage or can I pour right up to it, ostensibly using the walk and foundation as the form? Is there some reason that would be a bad idea? Can I pour it all at once? Will I need to cut it afterward to control cracking?

    Any advice is appreciated. Hopefully I've made the intent clear.

    Thanks and regards,
    Russell

  2. #2
    Join Date
    Dec 2006
    Location
    Woodinville, WA
    Posts
    30
    Russel,

    I recently completed a few concrete projects, but I am a novice so take my advice with a grain of salt. I poured a footer and a wall adjoining the foundation of my house. I read to use jointing boards (tar covered particle board is what I used) to keep the new structure separate from the foundation because if the new foundation settles and is connected it may crack the old foundation which is already all settled in. So from what I've read it is best to keep them separated.

    They had the jointing boards at home depot although when I asked noone knew what I was talking about. I ended up finding them myself.

    I'm sure you will get more comprehensive advice form some of the more experienced folks.

    Good luck!

    Jim

  3. #3
    Join Date
    Jan 2007
    Location
    Rio Rancho, NM
    Posts
    1,417

    Concrete Patio

    We put a 22' by 22' concrete patio at the house that we had in Virginia Beach.

    When I laid it out I put the expansion boards against the existing house and garage. I didn't want any cracking, so I laid 6" by 6" wire mesh in the concrete and the patio was still there when we sold the house 7 years later without a crack.

    As far as pouring it in one pour, it is totally possible but ensure that you have a few friends over to help in getting the concrete laid and finished.

    Time to have a party!!!! Supply the beer after the pour is done.

    Dave
    Nancy Laird
    dandnspecialties@msn.com
    FWW Registered Voter and Voting Member
    Woodworker, turner, laser engraver; RETIRED!!


    A veteran is someone who, at one point in his life, wrote a blank check made payable to his country for an amount of 'up to and including my life.' If you love your country, thank a vet.

  4. #4
    Join Date
    Oct 2006
    Location
    ABQ NM
    Posts
    29,079
    Quote Originally Posted by Russell Svenningsen View Post
    ...Do I need to form the sides that will abut the sidewalk and garage or can I pour right up to it, ostensibly using the walk and foundation as the form? Is there some reason that would be a bad idea? Can I pour it all at once? Will I need to cut it afterward to control cracking?

    Any advice is appreciated. Hopefully I've made the intent clear.

    Thanks and regards,
    Russell
    Hi Russell. Good to see you post. In a past life I was a civil construction inspector, so I've seen a lot of specs and construction practices. I picked up a lot of concrete slab and joint experience working on airport parking aprons that got heavy loads. To answer your questions...

    Jim was right about the need to isolate the new slab from your existing sidewalk and garage. The "jointing boards" he mentioned are also called "compression joint material". It's essentially Celotex, which like Jim said is a lot like tar-covered particle board, but it's somewhat spongier. It's about 1/2" or so thick by about 4" wide. You can simply place a layer of this on the edge of the existing concrete, and pour your new stuff right up to it. The walk and foundation do work as your form, but this just adds a bit of cushion for when the separate pieces of concrete expand and contract with temperature changes as they always do.

    For a slab the size you're talking about, I don't think you'd need to cut any joints in the slab, but you should tool "control joints" in the fresh concrete to direct where you want the concrete to crack. If you look at a typical sidewalk, you'll see that most of the "cracks" in the sidewalk and simple grooves that were made when the concrete was still wet. These are control joints. When the concrete cracks -- and it will -- it seeks the path of least resistance, so it tends to follow these control joints. You'll also notice on most sidewalks that every so often, you'll see a wider joint, usually with compression material in it. These are "expansion" joints, which absorb the shrinking and expanding the concrete does as the temperatures change.

    To determine how far apart control joints should be, a conservative rule of thumb is to take the slab thickness in inches, double that number, then make the joints that many feet apart. So for a 4" slab, the joints would be about 8' apart. If I were puoring your slab, I'd tool two joints to divide the slab into four 6' x 7' rectangles. You can get away with bigger sections (some guys will go more like 10' to 12' between joints), but eventually it will crack, so you may as well tell it where you want it to crack in the first place. You can go without joints at all, especially if you add 6" x 6" wire mesh like Nancy did, but eventually, the slab is very likely to crack, so in my opinion, it's best to tell it where to crack in the first place.

    They say there are three rules about concrete:

    1. It's gray
    2. It gets hard
    3. It cracks

    With dyes, you can change rule #1, but the other two are pretty much "cast in concrete".

    Hope this helps -
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

Similar Threads

  1. Be careful what you wish for! Seeking advice.
    By Randal Stevenson in forum General Woodturning Q&A
    Replies: 3
    Last Post: 07-13-2014, 02:11 AM
  2. It's a patio!
    By scott spencer in forum Carpentry and Construction
    Replies: 13
    Last Post: 07-12-2011, 02:41 AM
  3. Patio Furniture
    By Robert Kiles in forum Flatwork Project Showcase
    Replies: 5
    Last Post: 01-12-2011, 04:42 PM
  4. New patio roof
    By robert dewinter in forum Carpentry and Construction
    Replies: 17
    Last Post: 09-12-2007, 06:02 AM
  5. Seeking advice about the Rockler Drill Press Table
    By Frank Pellow in forum New Tools
    Replies: 16
    Last Post: 01-22-2007, 09:57 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •