Level Concrete Patio for Drainage


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Old 01-10-15, 10:23 AM
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Level Concrete Patio for Drainage

Hello - First time poster here :-)

I am planning a DIY project and trying to get some advice on how to best fix water drainage issues on my patio. I plan to screen in my existing and covered concrete patio. During rainstorms the patio collects some water and it doesn't drain since there is not a good slope to the patio. I thought it would be a good idea to remedy this issue before screening in the patio to prevent moisture problems. My patio would be screened in along the already existing 6 x 6 wood columns.

Looking ahead once the water drainage issue is fixed I am also considering installing tile over the concrete to make the floor appealing in appearance. I'm not committed to doing tile and would consider other suggestions based off the level of effort as a DIYer.

So for my water drainage issue I have looked around on the web and one suggestion I received was to use a diamond blade etcher to trim the patio so there would be adequate slope. I've also read about putting on an additional layer of concrete (and/or overlays??). When my patio was built the contractor did not include any expansion joints. So I have one or two hairline cracks that runs about 6 feet across the patio. While I do not think the cracks are a big issue I did not want to discredit them with any suggestions to fixing my water issue.

Thinking further along through the rest of the project when I install the wood framing for my screened in porch I will need to consider any water that enters the patio will need to exit the patio by flowing past the framing into the lawn. Besides pressure treated lumber is there a better way to handle this?

I provided a drawing showing the scale of the area. Also attached a few pictures of the area after a heavy rainfall a few months back so you can visualize.

Thanks for any help on what would be best for my project.

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Old 01-10-15, 03:15 PM
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Speaking of control joints, a well placed shallow kerf cut right through the dips would help drain a good percentage of the water from those lowest points. Would probably get filled with dirt eventually, but an air compressor nozzle would remedy that.

When you go to frame, shim your bottom plate up maybe 1/4" every 16" or so, then water can drain out.
 
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Old 01-10-15, 06:18 PM
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if roof over hang could be greater it would help, other hand a drain in concrete using small jack hammer hole big enough for post hole digger put rock on buttom of hole then a short pipe with a drain where seems to stay, use a good patch cement around drain might even give it a little depression.
 
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Old 01-10-15, 08:43 PM
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It's a shame whoever poured the slab didn't know enough about concrete to give it more pitch, and also install some control joints to define where the cracking takes place. If the house entry level allows, I'd consider pouring a bonded, concrete overlay on top of what's there. With a pitch of about 3/16" per foot, it will be about 2" thicker at the house end than the outside end. You could either lay tile on the overlay after it's fully cured, or give it an architectural finish (colored, textured, stamped, etc.), skipping the tile to make things more along more quickly and more economically.

I'd sawcut some control joints close to the existing cracks in the slab, then mimic those with sawcuts or grooved joints in the overlay. I'd also build a short pony wall all the way around, in an effort to keep the bulk of rain and snow from blowing through the new screens.
 
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Old 01-11-15, 01:02 AM
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@XSleeper - I do not think I've heard of this idea before but it seems pretty effortless to complete. How would a kerf hold up if tile is installed on top of it? Judging by the placement of my low spots I don't think a single kerf going lengthwise with the patio would work. Instead there would 4-5 kerfs down the patio that dumped water between the posts.
 
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Old 01-11-15, 01:07 AM
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@jargonize - I like the idea of a drain, but I do not think a single drain would fix my issues so I'd be installing a few to catch the water.
 
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Old 01-11-15, 01:16 AM
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@BridgeMan45 - Pouring another layer was my original plan, but I figured there had to be an easier way. Or perhaps I was over thinking it. The new layer would cover the entire patio right? I'd essentially be installing a new patio.

I was originally considering the screen to be a full screen / top to bottom system. However the more I think about the rain/snow I will seriously consider a design that offers some protection on the bottom against the elements.
 
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Old 01-11-15, 02:44 AM
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Installing sawcut kerfs won't be effective if you plan to install tile on top of the concrete. Very little free water will filter through the tile and grout to get to the kerfs and drain. Tapered sawcuts work quite well by themselves (based on my own experience, trying to correct a previous owner's finishing screw-ups), but all bets are off if you cover everything up with tile).

An overlay is essentially giving yourself an entirely new patio surface. But be careful, because if you don't know concrete, or what you are doing, you won't be happy with the results. Maybe it's time to "let your fingers do some walking"--meaning call in some concrete people who have overlay experience (keeping in mind that very few concrete contractors do, based on personal experience).
 
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Old 01-11-15, 11:18 AM
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What are your thoughts on using a floor grinder to add the necessary slope?
 
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Old 01-11-15, 07:57 PM
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You're more of a man than I am if you plan to grind the entire area. I've only used a walk-behind grinder a few times, and both times it got ugly, real fast. I was only doing surface scarification, and getting old carpet glue/crud off before laying ceramic tile. The tremendous amount of concrete dust generated made it almost impossible to accurately see the rate of progress (spent as much time sweeping as I did grinding), and I was only removing barely 1/4" total. Even though I thought I was wearing a decent dust mask, spitting up dark gray slugs for several days after told me it wasn't that good a mask. I can't imagine trying to grind off up to 2" of concrete over a large area, and doing it uniformly enough so there weren't large ridges and valleys. Thinset is forgiving, but can cause problems if placed with too much variation.
 
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Old 01-11-15, 10:11 PM
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Even though vacuum attachments exist I would agree a grinder sounds like a pretty nasty job. This got me looking around and I found concrete scabblers and scarifiers. Just at a quick read a scabbler seems to remove concrete more aggressively. I have no experience with this equipment. Do you think either is a good fit for my project?

I appreciate your recommendation to do the overlay through a contractor, but it seems to be a pricey job for my DIY budget. I'm not convinced I want to take on that job personally, but I would reconsider it. I really like the kerfs however installing tile on top of it would be pointless as you mentioned. Instead of tile do you think outdoor carpet be a better fit for kerfs?
 
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Old 01-12-15, 10:18 AM
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A cold-milling machine is what would work, but I've never seen one small enough (portable) for use on a patio. I have more than 20 years of DOT experience with scabblers (including more than a few hours running several of them), as they were our primary source of bridge deck preparation prior to installing concrete overlays. If the concrete being worked on is of low strength, using one might do what you want in terms of material removal. However, if it's average or better, forget about it--you will be scabbling for several days, with possible questionable results. Also, removing 2" of a typical 4" slab thickness is likely to result in significant cracking in the remaining slab, from the impacting vibration imparted into the mass of concrete they're used on (our bridge decks were usually a minimum of 7" thick). The rental cost of a heavy-duty 400 CFM compressor needed for operation is another factor to consider. Scarifiers typically remove a lot less material than scabblers, and are what's used to prep concrete surfaces for bonding overlays to.

I suspect that carpet over kerfs won't make you happy, with the mold and dirt accumulating under the carpet never drying out.
 
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Old 01-12-15, 11:30 AM
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What about the possibilty of cutting out a 6" slot of concrete near the front wall, then put in a perimeter drain tile/grille that would drain out to each side (under side walls)? Floor leveller and/or thinset under your tile could fix the dips.

But unless you add the 2" slope like bridgeman suggests you will prob always have some standing water somewhere.
 
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Old 01-12-15, 05:21 PM
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I've been checking online with some of the local equipment rental shops and seen a variety of surface prep machines available. I'll have to call around to describe the project and see if a cold-milling machine is available.

As for the 6" slot of concrete...can you explain further? I don't understand the location and placement in the patio.
 
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Old 01-12-15, 05:30 PM
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Something similar to this. http://northrangeconcrete.com/images...ench_drain.jpg

But the entire length of the porch, near the front wall. If you are going to continually be getting rain through the screens it might be a good idea to put in something like that that is continuous across the entire front of the room, close to that front wall.
 
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Old 01-12-15, 08:39 PM
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Okay now I understand. I think the patio still needs the slope though to get water into the drain.
 
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Old 01-12-15, 10:02 PM
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I did a little more research and found something that may work. I have 2 equipment rental shops that may have walk behind scabblers available for rental. Based off the models posted at the rental sites I was able to read up on them at the manufacturer site. If I get anywhere close to this performance as reported on the website I think I will be okay to do the job myself.

So I run the scabbler creating the slope I need then come back and do the tile thinset.

Removes up to 250 sq.ft. per hour at Depth Per Pass of 1/4″

Scabblers Archives - EDCO
 
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Old 01-15-15, 06:19 AM
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Any suggestions on how to best measure the slope of the patio as I trim away the concrete?
 
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Old 01-15-15, 09:47 AM
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To find out how much to take off, I would flood the patio and find where the water is deepest. I would run a 4' level from the outside edge of the patio to this deep area. Measure the difference between deep area and the outside edge with the level, level. This what you need to remove to make the deep area level with the outside edge. From the pictures it looks like the outside edge is higher than most of the floor. Trim the edge down so it is level with the deep area or better yet 1/8" lower and the rest of the floor will drain.
 
 

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