Anyone here do this, done this, had it done?
I’ve been looking for ways to save/repair a patio. It’s an L-shaped slab about 16′ x 20′ divided with a control joints into six 4′ x 10′ areas. The slab is at least 30 years old, probably much older. Its appearance hasn’t changed much that I can remember.
Two pieces of the slab have been broken for the duration of my memory. They have sunk and are at least 1″ lower than the others. There is one other crack as well.
I’m trying to come up with some feasible options. Here’s a list of possibilities:
A.Mud-jacking / slab-jacking the broken portions back into place
B.Cutting the broken portions out, place compacted fill underneath and fill hole with new crete
C.Demolish entire slab and pour new.
I’m leaning toward option “B”. It would probably be the easiest and cheapest, based on my limited knowledge.
As an aside I’m going to put a roof over part of this and tie the roof into the house. Roof would be a gable about 15′ wide, protrude 5′ from the house. Redwood post would support the roof structure and have to tie to the concrete somehow.
I was thinking of drilling the patio and epoxying threaded rod into the crete with bolt-down post bases. I don’t know much about the thickness of the slab or how it will behave when I start drilling. Any other ideas or things I should be concerned with?
The crooked lines are the cracks.
Edited 6/26/2007 7:02 pm by jase
Edited 6/26/2007 7:03 pm by jase
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crooked lines are cracks.
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My tendency would to remove the existing, repair the subgrade, and re-pour... but I have easy access to flatwork guys and zero access to a mudjacker. Still, your slab sounds like it's borderline as far as investing more dough in it.
Repairing the subgrade can be the problem. If you don't do that, any new work will fail. Mud jacking does a halfway reasonable job of "repairing" the subgrade, OTOH.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I've been through the phone book and haven't been able to find a mudjacker. I don't want to tear out the whole patio; that would be more work than I want to do, especially if I don't have to.This is my dad's house. I'm almost as cheap as he is when it comes to fixing things, which is why I'm leaning toward cutting out the bad spots and fixing those.Jase--Is there a better way?
I think they're listed in the Yellow Pages here somewhere under "concrete". [Yeah, under "concrete restoration".]You might ask around -- mudjackers tend to be small contractors who don't advertise a lot but get jobs by word of mouth.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Had our driveway and apron next to the house mud-jacked about 25 years ago. Two inches at points, IIRC. Some of it's settled back an inch or so, but I'm still quite satisfied with the job.
Far-far cheaper than demo/rebuild.
While you are removing the damaged areas for repair, auger some holes and pour concrete piers for your posts. Anchoring them to a slab that is a) of unknown thickness and b) already failing is not the best plan, IMHO.
Mike Hennessy
Pittsburgh, PA
Jase,
Some things to consider:
Option A: You may get it back to level, but how long will it stay there? I had a nice level driveway, albeit with some cracks, until the neighbors put in a new sprinkler system. The additional water in the soil caused a big section of the drive to lift up an inch as the soil expanded. With concrete, the most important part is what's underneath. Even if it stays perfectly flat forever, the crack(s) will be ugly. There are resurfacing products that you might want to look into; one such is: http://www.concretesolutions.com/. I found them more them more than 10 yr's ago, so they aren't fly-by-night.
Option B: The new slab portion will almost certainly not match the others in color, and may stick out like a sore thumb. If you go this way, I would want to connect the new section to the old with pieces of rebar drilled/epoxied into the old slab(s) and bedded in the new.
Option C: If you go this way, make sure they properly prepare the base taking into consideration drainage & soil type in your area. Also consider wire and/or added fiber to reduce cracking.
Lastly, regarding your post(s), do not, not, not, not, use the exiting (failing) slab or even a new slab as the footing. Set the posts on a properly constructed footing that extends well below the frost line for your area. I'm in the process now of re-footing a carport post (actually a concrete filled lally collum) that was just set on a standard walkway slab and which has now subsided about an inch and a half putting the whole structure in danger of heeling over. The fun part is that the colum supports a 3-way junction of 4x12's that are only connected together by the lags in the column flanges, but that's another story.
a oncrete paito really doesnt weight that much . if you have a 20 x 20 patio 4 inches thick, thats five yards, a yard is close to a ton. 2000 lbs. that would be 19575 lbs per five yards. 400 sq feet in a 20x20. Thats 48 lbs per square feet. If you soil will not hold 50 lbs a sq ft. you really have a sub soil problem.
Failures such as the OP describes generally occur due to incomplete compaction of fill under the slab. For this reason the worst areas will generally be closest to the house.If any portion of the slab is replaced, care should be taken to compact the fill reasonably well (but don't over-compact as that could cause the replaced areas to stand proud as the rest continues to sink).
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Dad's got a nice neighbor with a Bobcat who's going to take the slab out this weekend...for nothing! Next week we will build a new patio with footings for the roof-carrying posts. We will be able to properly prepare the grade and create a path for drainage. My mother has lots of plants on and around the patio (read constantly wet patio) and there are two downspouts that dump near the slab with no drainage path.
Thank you all for your input. I wasn't able to find a mud-jacker. It eases my mind that the patio will be redone right and the drainage issue will be addressed.