Smoothing/leveling concrete slab


  #1  
Old 07-04-14, 11:25 AM
J
Member
Thread Starter
Join Date: May 2013
Posts: 9
Likes: 0
Received 0 Likes on 0 Posts
Smoothing/leveling concrete slab

Hello everyone,

I just had a concrete contractor out to pour a 17x22 ft. slab for us. I informed the contractor that I wanted the slab in order to level the area in preparation for pavers atop the slab. I realize that crushed gravel and sand is the standard method, but for such a large area, I decided to opt for the concrete slab instead and let the contractor level the area.

He informed me that the slab would be "rough" when done, and I agreed since we were going to cover it anyway with the pavers. As you can see from the attached pictures, "rough" was well beyond what I expected. I was under the impression that "rough" meant like sandpaper, not a hiking trail; I cannot imagine that a contractor would think this surface would ever be acceptable.

Now we have a rocky mess in our back yard, and I would like to know what would be the most cost- and time-effective method of salvaging this debacle so that we can install our pavers atop this "slab."

Thank you for any advice.
 
Attached Images    
  #2  
Old 07-04-14, 11:42 AM
Rough Rooster's Avatar
Member
Join Date: Feb 2014
Location: USA
Posts: 446
Received 16 Likes on 12 Posts
Facing your dilemma, I would use a brick laying mortar (enriched with some Portland) and lay the tiles in that.
That is an inexcusably BAD job.

RR
 
  #3  
Old 07-04-14, 12:21 PM
J
Member
Thread Starter
Join Date: May 2013
Posts: 9
Likes: 0
Received 0 Likes on 0 Posts
Rough Rooster,

Thank you for the reply. Forgive my ignorance, but I would like to do this job only one more time, so which type of mortar should I use? I have found Fast Set Repair mortar and Type S mortar at Lowe's, but I am uncertain if either of those would be appropriate.

Also, do you think it would be useful to set the perimeter stones in mortar and then use a 1" layer of sand for the interior stones to ensure drainage? I have read conflicting advice.

Thank you again.
 
  #4  
Old 07-04-14, 12:23 PM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 28,345
Received 1,629 Likes on 1,462 Posts
I agree, that is a very bad job. That rough a surface will make it more difficult to trowel out your mortar and not get air pockets. It can be done but it does not make your job any easier. I might even consider giving the pour a scratch coat of mortar to get it up to a more friendly texture for the final laying of the pavers.

Before laying your pavers I would look over the pour after a rain or give it a good soaking with a hose. Look for any puddles. If you notice any areas that are not draining plan to compensate for it when laying your pavers.
 
  #5  
Old 07-04-14, 12:43 PM
czizzi's Avatar
Member
Join Date: Jul 2007
Location: USA
Posts: 7,388
Received 15 Likes on 13 Posts
Who pours concrete to lay concrete squares on? Why did you not just have a contiguous slab pours and they treated to give an aggregate look?

Anyway, the key here is not looks as it was never meant to be a finished surface. Is it level?, and if so, I would put some sand down, lay the pavers, sand again between the stones and enjoy the patio. All you need is an approximate surface as the sand will act as the final bed for the pavers.
 
  #6  
Old 07-04-14, 01:47 PM
S
Member
Join Date: Dec 2013
Location: usa
Posts: 1,348
Received 1 Like on 1 Post
nevermind that pavers aren't design'd to be laid on conc, you may be lucky,,, NO mortar - just a screeded sand bed,,, place the pavers, set them w/hammer, & broom in polymeric sand to hold in place.

pavers are known as ' flexible pavement ' in engineering terms - also ' engineered cracking pavement ',,, unfortunately the same can't be said for your conc,,, UNLESS there are contraction jnts in it, the conc will crk where IT wants to crk,,, had jnts been properly installed, it would still crk BUT where YOU want the crks,,, then you could have aligned your pavers to ' fit ' the pattern.

we just got a 200sy paver job - the other bidder wanted to also place conc 1st,,, to the h/o, conc does sound stronger & it is,,, its just NOT flexible NOR a good base for pavers.

where's you ever get the idea you needed conc for a base ?
 
  #7  
Old 07-04-14, 02:35 PM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,110
Received 4 Likes on 4 Posts
I can't tell from the pic, but if the slab is at or above ground level, you'll need some sort of edging material to hold the sand in place if you go that route.

What kind of base material was put in, if any at all? 17 x 24 and not a single relief joint? That guy is doing the whole profession a disservice by calling himself a contractor.
 
  #8  
Old 07-05-14, 02:20 PM
S
Member
Join Date: Dec 2013
Location: usa
Posts: 1,348
Received 1 Like on 1 Post
backing up the slab should resolve that little issue - he'll figger that out soon enough, o' great super-moderator
 
  #9  
Old 07-05-14, 04:03 PM
J
Member
Thread Starter
Join Date: May 2013
Posts: 9
Likes: 0
Received 0 Likes on 0 Posts
Thank you all for your feedback. In reply to the questions regarding why I chose concrete for the base, the reason was primarily financial. The concrete was less expensive than the paver base, but I now see why--because the contractor apparently is incompetent. Unfortunately, we are not going to jackhammer what we have and start over since that seems wasteful, so I think a combination of suggestions will be the chosen route:

First, I plan on laying a scratch coat of mortar around the perimeter to level that part out. Then, I will lay the edging stones in that mortar so I have a perimeter to keep the interior sand in. Then, I will add a layer of sand (1" or so) to the interior of the slab and then lay the pavers in the sand and finish with polymeric sand in the joints as suggested.

I suppose I can only hope that the underlying slab does not crack too severely, but it sounds as if the lack of relief joints may be a significant issue in the future.

Thank you again for your suggestions and (unfortunate) confirmation of the complete lack of knowledge of my contractor.

Please let me know if any of my solutions seems unfeasible. Thanks.
 
  #10  
Old 07-05-14, 04:09 PM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,110
Received 4 Likes on 4 Posts
I'm not sure, but you may be able to saw relief joints now, so at least if you get cracking you'll know where they are? Better to have a crack between pavers as opposed to in the middle of one. Did he use wire or rebar at all?

I think you might even be able to do the cut joints with a circular saw and appropriate blade, though renting one designed for the job would probably be better.

If the guy was licensed in any way, I'd definitely report him to the BBB and local/state office if you have one.

I'm really surprised that the concrete was cheaper. I mean, whats in it? Rock and sand...same as normal paver base (different materials of course). Bulk deliveries are normally pretty cheap if you talk to the stone yard nicely.
 
  #11  
Old 07-05-14, 04:27 PM
J
Member
Thread Starter
Join Date: May 2013
Posts: 9
Likes: 0
Received 0 Likes on 0 Posts
I was surprised as well, which should have been my first warning. Nonetheless, I think I will investigate getting a masonry blade for my circular saw and making the relief cuts along the paver joints as you suggest. He, of course, did not use any wire or rebar to my knowledge, so hopefully cutting the concrete will be more feasible.

Should relief cuts be made along each paver column, or only along a few columns? We are using 16" pavers. Thank you again.
 
  #12  
Old 07-05-14, 04:52 PM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,110
Received 4 Likes on 4 Posts
Should relief cuts be made along each paver column, or only along a few columns?
That would be a Pro question...I would think maybe one perpendicular to the 17 ft section (8.5 ft x 24 ft sections), and at least 3 across the 24 ft (making 8 ft x 8.5ft sections).

If you use your own saw, beware of the dust. It will absolutely eat your bearings alive. Wet the slab and then keep a small trickle of water running. It shouldn't be a shock hazard as long as you are plugged into a gfci and the saw is double insulated.
 
  #13  
Old 07-06-14, 02:25 AM
S
Member
Join Date: Dec 2013
Location: usa
Posts: 1,348
Received 1 Like on 1 Post
its too late to cut contraction ( relief ) joints as the conc's already developed micro-cracking in its need to relieve the tension created by the curing process - that's my story yada, yada, yada,,, 1 could diamond saw full depth to achieve proper slab dimensions - how thick is the slab - it wasn't posted in the original thread,,, iirc,14" blade on a demo saw will cut 5" deep, 4" for a 12" blade,,, jointing pattern is the most important item to prevent random cracking & must be done while the conc's uncured as much as possible.

looking back @ the pic, all agree there was no screed, bullfloat, or trowels,,, did the installer use a jitterbug ? that would account for the surface condition & the failure to properly communicate would take care of the rest - just asking,

however, most ignore my advice nevertheless, GFCI device on the ext cord outlet & no more than 50' of ext cord - more than that, use 12/2 ext cord ( 20amp ),,, f the masonary blade - it wears too fast to maintain same depth start to finish,,, use diamond blade - preferably a dry-diamond & wet-dry vac,,, snap your lines & immediately spray w/spritz bottle of hair spray to they don't disappear while you're cutting,,, you'll find 1/4 OR 1/2way thru the job you shouldda rented a demo saw

supermod's absolutely right on his dimensions !

good luck !
 
  #14  
Old 07-06-14, 04:03 AM
B
Member
Join Date: Oct 2001
Location: USA
Posts: 996
Received 8 Likes on 8 Posts
Before you start setting pavers, I would suggest you do some research on pavers set on a concrete base in an area subject to freeze/thaw. There is something in the dark recesses of my old brain that there are some things to do and not to do. It all goes back to some pretty dramatic failures on the Minneapolis Nicollet Mall many years ago (mid-eighties?). I'm sorry I don't remember any of the dos and don'ts any more, I just remember the failures and the contractor having to redo thousands of square feet of pavers.
 
  #15  
Old 07-06-14, 06:05 AM
Norm201's Avatar
Member
Join Date: Sep 2013
Location: United States
Posts: 11,497
Received 625 Likes on 555 Posts
I like what Stadry is sayings. Pavers are not meant to placed on concrete slab. You need a base that can drain away water and a "bed" of sorts that the pavers will sit into and not erode away.

You already have a slab. I would make the best of it. You can have a scim coat put on to smooth it out and/or have an imprint type of pattern poured into it to simulate pavers.
 
  #16  
Old 07-06-14, 07:37 AM
S
Member
Join Date: Dec 2013
Location: usa
Posts: 1,348
Received 1 Like on 1 Post
in fairness to the dumb contractor, no one here knows what plans & specifications were drawn & upon which he submitted a bid,,, engineers & architects do get it wrong - that's why so many of them have to pay claims
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: