Bricks, Masonry, Asphalt and Concrete - slab for central air unit....
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cliff&kim
03-02-02, 06:53 AM
I know it's a basic job, but I've never done it before. How big, how thick, best concrete mix, etc. Input appreciated. It's a 3 or 3-1/2 ton(haven't gotten it yet).:cool:
the_tow_guy
03-02-02, 12:14 PM
Pretty straight fowrard work, but can't be hard on the back, etc.
You'll want to make it a little bigger than the unit that will sit on it. My 4T is about 32x32", so far argument sake lets say 36x36".
Locate where you want to put the slab and level the ground out as much as possible. Make your forms out of 2x4'; cut two 39" and two 36". Nail together to form a square that measures 36x36" inside. Lay form on prepared site. Drive wooden stakes on the outside of each side to hold form in place; make sure top of stake is driven below the top of form so as not to impede finishing the surface after pouring.
For this size form you will need approx 2.6 cu ft of concrete. Size of the concrete bag will determine how many you will need. Most home centers carry Sakrete, Quickrete, or similar. As I recall one of the standard sizes is .6 cu ft of which you would need 5 bags. Always buy at least one extra bag; really sucks getting started and finding out you don't have enough.
Get out your mixing tools: Shovel and (reasonably) clean round trash can that will hold liquid (no big holes). Mix your concrete 1 bag at a time (2 if you're strong and amibitious). Empty bag into trash can and add proper amount of water (bag should tell you how much per bag; their suggestion I've found is often a little too dry. You don't want it soupy, because it will be weaker, but you want it moist enough to work also). Now mix it up by tipping top of trash can at about a 45 deg angle and rolling the can just like a cement mixer; make sure all the dry concrete mix gets moist and well-mixed. If you discover you've made the mix too wet, just open your next bag of concrete and add some more dry to the mix you're working on. Dump into form starting at one side/corner. Continue to mix and pour until form is filled up. Use a small gardening trowel to make sure concrete is well into corners and against forms. Now level off the concrete in the form by laying a long piece of 2x4 (on it's short side) on the top of form boards and moving it across. Move board back and forth as you work across form for best results. When surface is to your liking stand back and admire for a couple of hours until the surface starts to firm up. Now cover with clear plastic and leave it alone for about 5 days or so. Alternately if you don't want to use plastic, dampen the surface with a hose several times a day for 5 days.
Form boards can be removed after the first day, or if you use pressure treated you can just leave them in place (did that with a pad I laid for my daughter's portable b-ball goal).
Good luck.
You'll want to make it a little bigger than the unit that will sit on it. My 4T is about 32x32", so far argument sake lets say 36x36".
Locate where you want to put the slab and level the ground out as much as possible. Make your forms out of 2x4'; cut two 39" and two 36". Nail together to form a square that measures 36x36" inside. Lay form on prepared site. Drive wooden stakes on the outside of each side to hold form in place; make sure top of stake is driven below the top of form so as not to impede finishing the surface after pouring.
For this size form you will need approx 2.6 cu ft of concrete. Size of the concrete bag will determine how many you will need. Most home centers carry Sakrete, Quickrete, or similar. As I recall one of the standard sizes is .6 cu ft of which you would need 5 bags. Always buy at least one extra bag; really sucks getting started and finding out you don't have enough.
Get out your mixing tools: Shovel and (reasonably) clean round trash can that will hold liquid (no big holes). Mix your concrete 1 bag at a time (2 if you're strong and amibitious). Empty bag into trash can and add proper amount of water (bag should tell you how much per bag; their suggestion I've found is often a little too dry. You don't want it soupy, because it will be weaker, but you want it moist enough to work also). Now mix it up by tipping top of trash can at about a 45 deg angle and rolling the can just like a cement mixer; make sure all the dry concrete mix gets moist and well-mixed. If you discover you've made the mix too wet, just open your next bag of concrete and add some more dry to the mix you're working on. Dump into form starting at one side/corner. Continue to mix and pour until form is filled up. Use a small gardening trowel to make sure concrete is well into corners and against forms. Now level off the concrete in the form by laying a long piece of 2x4 (on it's short side) on the top of form boards and moving it across. Move board back and forth as you work across form for best results. When surface is to your liking stand back and admire for a couple of hours until the surface starts to firm up. Now cover with clear plastic and leave it alone for about 5 days or so. Alternately if you don't want to use plastic, dampen the surface with a hose several times a day for 5 days.
Form boards can be removed after the first day, or if you use pressure treated you can just leave them in place (did that with a pad I laid for my daughter's portable b-ball goal).
Good luck.