Ok boys and ghouls. I’m bidding on a rather large deck that consists of 9 seperate piers. When the deck package was drawn up, no one seemed to recall a concrete patio underneath the area where the deck was going. Now, it seems, there are a lot of piers that need to be placed on that patio. I know that some of you want me to say, “Duh, you think a 4 in. patio will support all that dern weight?”, but I won’t. I’d prefer an opinion of whether it’s smarter to just saw cut the concrete and then dig the piers or to tear up the whole pad. I’m assuming that saw cutting will be the easier way, but sometimes I like to type my thoughts out to get things straight.
Wes
Replies
How big is the patio? The only reason I can think of that you would want to tear it up is to avoid the patch job after the pads have been poured. If you don't mind the patches then cut and dig is the way to go. I see em all the time on the street and at the mall where they've added a pad for a new lamp post or somehting. the cut and patch marks are a little unsightly but maybe someone knows of a way to put some sort of coat over the whole patio......just an idea.
Around here it would be easier for me to have an excavator remove the slab. They'd show up with a 10 yard truck towing the machine, pull the machine off and break the slab, throw it in the truck, get back on the trailer, and leave. If you cut the slab you will still have to break up the chunks (I assume) and haul them away (I assume again), and then dig your piers thru the holes you cut. I'd just start with a clean slate if you can.
I only say this because every third guy around here is an excavator with a big Kobelco or Hitachi and a ten yard Mack to tow it around. Plus, you can take plain concrete to the gravel pit and they crush it, so no disposal cost.
Any reason you can't pour a 24"x24"x12" footing on top of that 4" patio slab? Then set your sonotube on that and pour the pier. That should spread the point load so the slab won't pie-wedge on you. What's the depth of the frost line in your area? Are there any frost-heave cracks in the slab as it now sits?
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
I'd want to know about the soil under the patio slab. Does the slab have any steel in it? How old is the concrete ( if you can't get machinery in there). What do the plans call for? Will you need an engineers stamp? Do you live in an area with a big snow fall?
Diamond saws work great but rebar is hard on the blades and can cause excessive wear ...= $
Good Luck
if the deck is attached to the house and you live in a frost zone, ya gotta dig it, in the great white north that means 6' and an expanded base .. (in 96 the frost went down 10' in our area!!!!)