View Full Version : Concrete slab repair question

09-17-2005, 07:47 PM
:confused: I also put this in the Plumbing section, but think maybe it belongs here.

My plumber sawed long trenches in my slab to lay down a new sewer line for a new toilet in a remodeled bathroom. The trenches are about 10 inches wide and 12" to 18" deep. I can find nothing to tell me how these trenches should be repaired to insure a stable slab. I have seen something about epoxy for the rebar. What is the expoxy and how should it be used? What should be done about the water barrier plastic? Any suggestions would be greatly appreciated, because he is planning to just fill up the trench with concrete and have me sign a release. :eek:

09-18-2005, 05:57 AM
just let the man do his job, don,t worry it to death!

master plumber mark
09-18-2005, 06:06 AM
we do it that way all the time....

usually , we take the fill and jujst put it back in then
fill the trench with about 4 inches of concrete...

its no big deal....it isnt going to hurt the stability of the slab
and their is no problem with a vapor barrior...


but if you are really going to worry yourself to death,
you can always go out yoiurself and buy a roll of black visqueen
at lowes for about 10 bucks for a 10 x 50 foot long sheet..

just insist that he at least roll it out in the
trench after he has backfilled the dirt back in ...
then tuck it into bed on the sides of the trench....

its about as good as you can do if it eases your mind.

if you absolutely must...

I doubt he is going to grumble too much about
a small amount of extra work like that either...

have some doughnuts and coffe ready for them
the day they do this phase of the job....

09-18-2005, 07:20 AM
Put the dirt back in the trenches, but because it was saw cut, the edges of the concrete are straight and smooth so the inserted concrete could slide down if the dirt settles. Anything that ties the new concrete to the old will prevent this. Rebar inserted into holes in the existing concrete, or cutting depressions into the sides of the cut so the new concrete is keyed to it, are two ways to lock the two together.

09-18-2005, 08:24 AM
hilti makes a 2 part epoxy thats used in concrete for threaded rod. definitely overkill. put the fill back in. tamp as much as you can. you could wet it to compact further. and shoot concrete nails into sides of the cut. dont sink them. and this will help tie in the pour.

09-18-2005, 03:07 PM
I was concerned that the new concrete would sink as the soil settled. Perhaps cutting at an angle would have been a better way. What tool will make the grooves? (I know he's going to ask)

09-18-2005, 03:57 PM
your plumber did the cut to the standards of the trade. you can rent a roto hammer drill ,and drill holes every 16" on both sides, install re=bar dowels
and maybe one 1\2" bar the length. this is never done and would be an EXTRA

master plumber mark
09-18-2005, 04:23 PM
that poor plumber whoever he is
will be getting onto this site to tell us all to mind our own
business and leave his alone...

if he just tamps the dirt down just a litttle with the
end of a sledje hammer, then simply pours in
the concrete it will work fine, unless you plan on
having a herd of elephants living in that space.
(or my sister-in -law)

you could lay some rebarb in the hole and you
could lay some visqueen through the bottom of the
trench over the top of it all if you absolutely must,
they wont hurt, but are not really necessary.

So as long as the poor guy is pouring a fairly thick slab
of concrete throughout that trench, lets say 4-6 inches thick,
it really aint gonna matter probably in all our
natural lifetimes.

We will all be dead and gone probably 75+
years before trouble will ever start , if ever....and thats not bad.

what are you going to nit pick next---- radon mitigation???

let the man do his job.

09-18-2005, 05:18 PM
so how big is your sister in law? is she single?

09-18-2005, 08:24 PM
so how big is your sister in law? is she single?

He implies that she is a double wide, not a single. Anything that creates an imperfection in the cut sides will key the new concrete the old. There is no concrete cutter in existance who would attempt to cut the concrete on a bevel, even if their saws could do it, which they cannot;

master plumber mark
09-19-2005, 03:54 AM
oh I wold put her at about 375
give or take 20 lbs.

09-19-2005, 05:12 AM
too much woman for me! betcha she could compact some soil!

master plumber mark
09-19-2005, 05:30 AM
when she is in town she stays with us.. its ok..

the good thing is she lives far away and is not
around all that much, x-mas --ect
the kids like to see her and she baby sits -- so its tolerable.

but when she walks through my office my computor monitor

actually starts to wobble on its paltform..

its like a herd of wildabeasts on stampede..

09-19-2005, 06:26 AM
Sounds like Al Bundy's mother in law.

09-19-2005, 12:42 PM
Master Plumbing is right on. (No comment on his sister-in-law)

09-21-2005, 08:47 AM
He laughed when I asked him about just filling the channel and then pouring concrete. He said that what they typically see in this area is holes drilled and rebar epoxied. He said the channel will have to be widened to allow room for the drill. We live in earthquake country and that soil/concrete will settle...

You won't have to put up with a tirade from my plumber, who happens to be just great to work with, BTW. He didn't really like the idea of just filling in the channel, either. I think he was just trying to save me money.

09-21-2005, 12:06 PM
The channel does not have to be widened. The rods do not have to be inserted parallel to the floor. Just drill the holes at the best angle you can with the drill. Once the rods are in place they are not going anywhere so even epoxy is not needed.

09-24-2005, 01:15 AM
Thank you.