I will be installing the drain pipes for my new basement floor, I know my layout and I've done a complete bathroom before, just not a basement bath. My questions are about breaking the concrete up.

(1) Use a saw, jack hammer, or sledge? From the reading up on this I've done:

Wetsaw
-i'm concerned about the precision of this so I don't take out more than needed, and cracking close to the external wall. This makes we want to go with a wet saw so I can do long clean cuts, but I've heard the dust and spray is unmanageable

Jackhammer or sledge.
-the replacement concrete holds better on a rough edge versus a smooth edge. This makes we want to go with jack hammer.

I've also heard of a guy that just went and bought a some masonry blades for his circular saw and cut the slab halfway, and finished it with a sledge. Cheaper

(2) In cutting the trenches, I was planning on making them about 10" wide and 12-18" deep. When the plumbing is in there backfill it with #57 put a vapor barrier down with some overlap if possible and pour the concrete. Is this normal procedure??

Hi RD:

Jackhammer and sledgehammer are what I've been using all my life. Once you get a hole started and you work the trench a bit you will want to dig out a little as you go and undermine the concrete you are chipping out... goes pretty darn fast if you use your head.

All the saws make one hell of a mess. If you try to plastic an area off the dust will just be unmanageable...

The rest sounded perfect!

MARK

Hi ragedriven

When I cut my French drain, I used a shop vac at exhaust for saw. Got most of dust doing at.

If heating system is in area, shut off and cover motor. Will suck in dust.

Good luck

Chuck

Rent a wet saw. The masonry blades for a circ won't allow water to be used there. The dust will be unbelievable and will burn out the bearings in a circ saw if cutting to long.

If you have an opening to exhaust residual dust out use it with a box fan to help it along. If you can rent a saw like this then use it.

Makita 4114 14" Angle Cutter

If all they have is this kind of saw only http://www2.northerntool.com/constru...tem-999000.htm make sure you can add a hose to it and adjust the water amount going to saw and section off that area to trap exhaust gas fumes and blow out a window or door, wear a good mask no matter what. . I personally use another man with a pump sprayer when cutting. If you tweak the water just right there's no dust and the water stays with the cut and it looks like wet slurry concrete and doesn't run all over the basement.

I prefer using an electric jack hammer for control and ease ( rental Store)
- Harbor Freight Tools - Quality Tools at the Lowest Prices

Don't worry about the crocked edge or a straight edge cut. Either or you need to hammer drill in the sides of the cuts and use 3/8 rebar about every 16" to re pour and Pin in new to old pour.

This #57 stone is a bit coarse. I prefer rice mix stone ( clean) for setting drainage and back filling the sub grade for conc floors. It spreads well to get slope for pipe and its dense in compaction so no tamping is necessary. The 57 is 1 1/4 to3/4. Stone rice is about 1/4 inch stone

massplumber2008, I like your idea of undermining the slab as I go to aid removal. I think I will go with the electric jackhammer, my local HD tool rental has one for $42. It comes with 4 different bits, one to get a hole started and some wider ones for trench lines.

Creahands, I'm glad you reminded me about the hvac, there is a return in the main basement area I need to block and shut off system. This will be a one man job, so having a 2nd man with the shop vac isn't possible, so a wet saw is out.

21 boat, I don't want to burn up my tools, plus a masonry blade is $20. I like your idea of a smaller gravel, like a #89 does sound better, spread the gravel around to aid with the sloping of the drains makes sense. So you think I should drill into sides every 16" and put a #3 rebar horizontally across the trench? That'd mean a lot more work, renting a rebar saw, but if it really makes a difference I will, because I don't want a water issue. Sounds like I'm going to need a concrete mixer too or a lot of buckets.

You don't need a rebar saw. A Carborundum " Metal" blade on a circ saw does the trick. If you want really fast cuts. If you rent a concrete saw to cut floor and the diamond blade to go with then pick up a metal blade to fit that saw arbor and cutting rebar is literally in seconds

Rebar is a must hear for perfect repair/re pour

Electric jack hammer doesn't require undermining the slab as you go . That's for sledge hammer style. The 90+ hammer is heavy and designed to do the job here. Not needing to undermine will save you time also. We have our own electric hammers and have no problems. Use the 2" chisel and break off 3 to 5 "lateral sections. Don't get over greedy breaking up concrete in BIG chunks. It takes More time then steady breaking.

Do it all the time sometimes weekly.

A wet saw is in if you rent one with a hose hook up for water. I only mentioned the pump sprayer to TWEAK the spray. I suggest if you use the wet saw get a ball valve for the end of your hose and hook up to tweak the water amount, The rented saws adjustments for hose hook ups are hard to adjust. Have three of those and even New they are difficult to Tweak.

If you have a shop vac then you are ahead of the game. Also if the water gets too much use some old socks and put Sand in them to make a miniature coffer dam so you have more cut time and don't have to keep stopping so much to suck up water. If you adjust your water to cut speed you can tweak it so close there is no to very little dust and the dry dust becomes like a slurry. I do cuts in hospitable concrete deck floors and that's how close a tweak can get.

To pour concrete back in just remember a yard of concrete is 46,656 cubic inches. Or 1,728 cubic inches to a cubic foot on concrete. To get an Idea of hauling and mixing crete a cubic yard of concrete is right at 4,000lb a cubic yard wet or dry plus or minus a couple of pounds. That will help you figure out the hauling pre mix bags to fill back in.

Hi Rage...

I have never used rebar to reinforce my concrete patches in 27 years and have never seen it done for residential underground work. Simply not necessary...

Undermining the concrete is usually only at the beginning phase to get things started.. once started, chipping should go quickly.

Finally, if you chip out the sides of the trenches so they are on a bit of an angle (see picture) this will assure a nice fit that will not loosen or crack. Use plenty of water to pre-wet the old concrete and the dirt in trench area before pouring the concrete.

Good luck...

MARK

Attached Images

 

Seen many of patches that sunk. All floors and houses settle through out the structures lifetime.
Sorry mass. What you have there is a "key way" cut. First to cut that a saw has to be at an angle. Or you have to sledge it that way.

If anything the 'key way" should be the opposite angle you show. Most all concrete sinks not rises in a basement unless we have hydraulics in pressure pushing against gravity.. and not to mention its just been dug out. That is also the reason for the smaller stone to have less chance of post settling and not be hollow under the patch if it does sink. If it sinks a 1/2 over time which can be likely the pins will solve that situation if it arises

The angle above wont stop any post settling which can be likely because the stone backfill is not being tamped and the concrete can settle past the "wedge"" or" or"above.

A good basic standard rule of thumb in the concrete world is to pin the old and new crete and that solves All post settling problems and covers for hydraulic pressure also.

Not to say about your patches but if anyone in the future wants to lay tile on there basement floor not physically tying it together can easily cause crack in the tile. It only takes a tiny bit for the crete to make that happen.

Look at how many questions on this site about cracked concrete in a basement floors and what to do to tile over it.

The other aspect its concrete and it doesn't know if its commercial or not. So if it works so well in commercial why not in residential and its cheap. One length of bar and a hammer drill bit. No dressing on the sides cut and patch.

Ragedriven was clear that he won't be using a saw. He will be using a jackhammer. Here, you use a jackhammer to cut angles in the trench. My angle is correct angle as it locks the concrete in and won't allow it to heave upwards.

Ragedriven isn't laying tile... he's installing plumbing underground. Even if he was, I assure you that when the dirt is compacted properly and the trench chipped as I proposed tile will not crack!

I am sure you have some good experience 21boat, but I'm also very sure that you are going overboard on the rebar. I also have some good experience... especially doing underground and patching.

Just my opinion

MARK

But it will allow it to sink downward which again is usually the biggest problem any concrete repair of road beds, or ANY excavated areas. Simply here you can't tamp a ditch well enough with the pipe in it in this situation because the pipe can't take that beating.

What about the next guy in tile or may have to deal over time the patch sinking...

Again I disagree with this angle and its wrong period. If anything it should be straight for the concrete to wedge its self. This wouldn't fly in my area or in basic concrete repair practices.

My good experience is 33 years of professionally pouring concrete commercially and residential and still counting. That's one of my main stays to support my heavy equipment. Do it for a living... Hard to get more Good expercience than that...

I don't know Boat,
You must have spongy soil in your area that you have so many patches that cave in.
We're not talking about a 4 or 5 foot wide trench here. When I make a patch I fill the trench up to with in 3 or 6 inches from grade tamping the soil down as I fill. I've patched many a slab that way with no complaints. But that's here, Perhaps you have different problems in your area. But unless the asker's in your area why rebar a small trench? While it sounds just dandy, and I like your reasoning, and there's no doubt he could install heavy equipment on the patch but it still seems a little like overkill to me. Regards, Tom

I'm not questioning your experience with concrete Mark but I guess I am with small trench work?

When you say, "you can't tamp a ditch well enough with the pipe in it in this situation because the pipe can't take that beating"... I have to wonder how many pipes you've laid in 10" wide trenches? You don't tamp them as much as you tamp the trench and then you soak the trench with water for awhile (on/off) so every cavity fills in completely. Concrete patch will never sink when done in this manner... remember... WE ARE TALKING ABOUT A 10" wide trench!

And I am sorry that I also disagree with idea that a floor heaving is better than floor sinking for tile. If patch rises it cracks tile. If patch dips/settles a bit you may not even notice via tiles.

Hey, I know we are from different areas, but I'm standing by the fact that rebar is unnecessary.

I WAS WRITING WHILE YOU POSTED TOM...good point on trench size. It is what I was thinking.

Well I see the gangs here

Quote above can be a factor here for trench width. Its not always just about a shovel width.

If he is Cracking a 10" wide ditch close to the wall as he puts it, the 10" wide ditch could get wider quick. Especially if a sledge is used here. The remaining crete to ext wall could be cracked and or loosened in the demo.

A shovel is 8+ inches wide. and the ditch is supposed to be 10" wide. Now, if the ditch is close to the ext wall and a conventional footer is there which is 18" wide to 24" wide with block in the middle so to speak. There will be a footer ledge on the inside. 4 to 6" or so under the floor. If the ditch is even 10" away from the wall that remaining floor could become cracked in the demo.

Nothing was mentioned about the exact distance from wall. The problem I'm having here is I'm trying to give the asker expert advice and some may think its over kill but I see a picture that isn't correct on design. On top of that I'm saying rebar is Cheap and you can't go wrong with it there's no gamble with it. So I'm giving the best advice for the asker on design not to Fail as an expert concrete contractor. So why is that such a problem here?? This is a concrete question.

Another thing I need to add. If the cut is a long lateral cut perpendicular to the wall then the original floor could lose it bearing on the footer ledge if bar is not used to tie all together. If the original floor had some post settling before ( and many do) the footer ledge was the structural strength for bearing of the floor and that could be compromised in the long run.

I do small trench work all the time especially when the residential plumbers call me to cut remove and pour for them being its cheaper for them since they don't have all the tools to do so or the trucks to haul or mix new crete or dumping old crete etc.

I also put in the inside drainage system to sump and re pour. Also the water that's along those edges could sink because of rains water getting under slab because it pretty much rains everywhere.

Again the angle is not correct. Don't know where it came from but its physically wrong and promotes post settling.

If patch dips/settles a bit you may not even notice via tiles.

I don't understand the logic here at all... either up or down isn't good period. So its will on the up to crack or a maybe on the down??

Why Not Do It Right and stop guessing it should maybe be all right without bar. I gave solid reason as to why to use bar and the ditch with is not the catalyst here. Seen 6" wide repairs sink/crack so what's the point...

I feel the asker here is asking about concrete more than plumbing. I feel responsible to give the asker my professional reasons and options here being that's my field. I don't have this problem when the plumber(s) ask me to do the concrete work. They comment is do it right and that's what I posted here.

We don't have the time to use the old running water approach. Besides that its been proven it takes many rains sinking in the ground for natural compaction.

So why is there such a problem here?? I'm not trying to step on anybodies toes here but at this point splitting hairs won't remedy the proper way to re pour the concrete.

I'm going to add my $.02 here, if I may.

I believe that the degree of "failure" whether it be sinking, rising, cracking, pitting does depend on the quality of the repair AND the conditions.

In my parts, near 21boat's parts, winter hovers around 32 and there is lots of freezing and thawing going on. In Speedball's parts, everybody's happy. In Massplumber's parts, when it's cold it's cold and when it's warm it's warm.

Thus, I believe, both Speedball1's and Massplumber's experience is sound. But in our part of the country, there are WAY too many expansion/contraction cycles to deal with.

Concrete isn't my thing, but I did help a friend (pour a basement floor and I laid couple of dozen of bricks, poured a post and fixed a few minor holes.

The building (slab/warehouse-like construction) where I worked, sunk various depths, max of about 1", at the concrete footers for the columns. To bad that while building didn't sink uniformly at the same time because the roof developed cracks along it's seam.

Gee, I wonder why that was.

BTW, when the pad was poured someone didn't pay attention to the prints. A large area probably 50' x 75' was supposed to be an isolated pad.

They had a novel way of pouring it. The poured the whole pad and then cut and broke up the center and poured the isolated center pad. Woops!

Interesting perspective on this Ron and Tom... :)

Mark, I'm not going to write a book explaining any more than I have. I made my points already. All that matters to me is that ragedriven is clear that rebar is not used residentially to patch a trench... not in Mass, Fla, NH, CT or anywhere else that I ever heard of until you brought it up... plain unnecessary!



MARK

Hey Guys!
Different areas, different codes, and different methods. We've all experienced it on this page. Look at the tussle I had with Growler over diswasher air gaps and tweaking Milos nose because UPC runs a dedicated vent on everything in the house including the family dog. Hey! We're pros here. We do the things in our area the way we do because they work for us. 21 Boat makes some compelling points. And it's true, rebar will beef up a patch. But I still thin k it's overkill for a small patch. In my area of Tampa Bay, Which covers New Porrt Richey, Tampa and points south to Port
Charlotte we don't use rebar in a single story slab. We use heavy iron grating that looks like fence that goes down over the visqueen. We use rebar on floors in our high rise condos. Is this better then what may be used in other areas? I don't know! But I'm not about to say other methods are wrong just becase we don't use them.
The bottom line here guys is, 99% of the time we're on the same page. We're professionals for Gods sake. It's not good for the page for the OP's to see experts bickering, although I'm guilty of it too. Let's wait and see what Ragedriven decides to do. Lord knows he's got ernough advice from us. Group hug?? Cheers, Tom

Bump

Are we happy again?

The Rebar that I mentioned is not about beefing up anything here whatsoever..

To help clear this up for the asker and I'm concerned if the other posters are confused then the asker may get confused also.

Everybody's brain here is going to the "strength" of the patch IE rebar. SO as rebar is mentioned most people think of compaction in strength/beefing.

This remark express and shows that mindset here and I feel adds to the confusion.. .

(and I like your reasoning, and there's no doubt he could install heavy equipment on the patch but it still seems a little like overkill to me. Regards, Tom )

Tom that's probably because you are still thinking weight/strength and not getting the pinning effect for the rebar I mentioned here.

The rebar stubs/pins here has nothing to do strength on the patch of this nature. Its all about tieing it in form new concrete to old horizontally. To maintain that flat horizontal plane through slight movement over time. 2" of rebar stubs sticking out of each side that is pinned into old Crete will accomplish that.

Maybe I should write a sticky note as to the many different uses of rebar and this won't happen

I'm not at all trying to bicker here. The asker may get crossed info.

I wanted this to be done with a while back, but the repost keeps adding confusion. It's not about what state the Crete is in . Its a patch and ALL Crete moves and cracks period. is Crete.

Too many times concrete is just looked at as "oh its just a concrete floor/patch, not unlike "oh its just a drain pipe" at one time.

Pinning a patch here with side pins is s not a code thing. If it was looked at like the plumbing world I chance to say the 'Pinning" would be a code thing.

Not upset here but this thing has been all over the states/ heavy equipment/ res versus commercial etc. Never would have imagined my post for a perfect good standard in Crete. floor patch would have this reaction. . Its 11 bucks for a blade and rebar that is in the big box stores.... How cheap is that for a 100% guarantee the patch wont move up or down ever unless the whole floor moves. It could be HOLLOW under the floor after the pinning is in and Crete sets up. The tamping in essence could be a waste of time along with the water method. As long as the stone/dirt stays still for the Crete to set up what happens under that patch is null and void for a 10" span with side pins to support that span.

Again sorry for the repost here but this should help clear up the diff on strength versus movement/settlement. Too many times concrete is overlooked in good building practices and misunderstood :)
Im done here at this point fingers are wearing out ;)

Regards to alll...

If you are putting down a subfloor then you should not have to worry about the tiles cracking if the patch sinks I am assuming