Opening concrete floor without filling the house with dust?

[JCH]

Need to open up our 60+ year old concrete basement floor to modify the main drain's piping. The hole will be about 1' wide by 3' long, adjacent to the basement wall. 4" cast iron drain goes into the slab at this point.

Which of these approaches would create the least dust?

- renting a jackhammer?
- using a masonry blade on either a circular saw or angle grinder?
- using a masonry bit on a hammer drill to drill holes every 1/4" or so and then knocking it out with a sledge?
- ditto except using a rented roto-hammer?
- something else?

Also, would wetting the area help keep the dust down?? Or is that just wishful thinking?

Thanks!

 

[DX]

A really good size jackhammer is fastest. Used properly, not too much dust. Tent the area and/or use a dust collector. Yes misting helps but not as much as a helper with a large funnel type dust collector held near the point of impact. If the slab is not reinforced (rebar) you need to be careful not to crack it beyond the area of interest.

The other options you listed are slow and dusty. You'll need a good respirator and plenty sandwiches

 

[Sponsor]

 

[JCH]

The slab is *not* reinforced -- it's a basic 60+ year old concrete slab. If I use a jackhammer, any specific techniques to avoid cracking the rest of the floor? Pre-scoring the surface with a saw? Or is it just luck?

And would a shop-vac qualify as a "dust collector"? Or is there something better suited?

 

[Gary Swart]

The best advice I can give you is to have a professional concrete cutting company do the job. Fast, clean, and neat. Of course they don't come cheap, but sometimes you're better off just biting the bullet and paying the man.

 

[DX]

Agreed, a concrete cutting co. may be overkill for 3 square feet, but breaking the slab close to the edge requires a bit of skill so you don't crack it to the outside edge.

This may be a job ill suited to DIY. Once you break the slab, do you have the tool and skill to cut the 4" cast iron? It will take a while with a hacksaw

 

[JCH]

This may be a job ill suited to DIY. Once you break the slab, do you have the tool and skill to cut the 4" cast iron? It will take a while with a hacksaw

The plumber is doing all the drain work. He's just asked me to open the floor up for him before he starts.

Thanks for the warning about cracking under the wall. Today I'll try drilling a line of holes with a hammer drill. I'm hoping that'll contain any cracks from spreading if I progress to using a jack hammer.

Or I'll see if I can find a pro.... Thanks for all the advice!

 

[Ballvalve]

Saw cut, @ 3/8" deep, drill holes every 5 inches, keep a hose running on all that work. Big hammer and its out and likely very clean. wet vac handy....

 

[Terry]

If you don't want to fill up your underwear drawer with concrete dust, hire a wet saw concrete contractor.

They come out with a large diamond tipped blade, cooled with a water spray. They hand you the wet vac to pick up the wet slurry from the cut.
No cracking, no dust, no ragged edges to pour to, and it takes no time at all. It's the least intrusive way to remove concrete. They will have all the tools on their truck, including all of the hand tools you can imagine.

These saws are hooked up with a garden hose for the water, clean cuts with no dust.

http://www.concretecutting.ca/pcc.htm

http://quickcut.ca/

 

[NHmaster3015]

Go down to the Depot and rent the big Hilti. Make a hole and keep on enlarging it. Have a shop vac running.

 

[JCH]

Go down to the Depot and rent the big Hilti. Make a hole and keep on enlarging it. Have a shop vac running.

What's a Hilti? A hammer-drill??

 

[JCH]

If you don't want to fill up your underwear drawer with concrete dust, hire a wet saw concrete contractor.

They come out with a large diamond tipped blade, cooled with a water spray. They hand you the wet vac to pick up the wet slurry from the cut.
No cracking, no dust, no ragged edges to pour to, and it takes no time at all. It's the least intrusive way to remove concrete. They will have all the tools on their truck, including all of the hand tools you can imagine.

Wow, that's quite the beast!

Not sure whether there'd be room for it to fit in this area... The 4" stack is currently about 3" from the foundation wall, and part of the cut is going under a 300 lb concrete double laundry tub (about 12" clearance underneath).

Trying to keep all the plumbing functional because there'll be a few day lead time between opening up the floor and the plumber being available. Don't want to be without plumbing during that time...

 

[Terry]

They carry smaller hand units in the truck too, they use those on the walls and for smaller cuts in the slab with little room.

 

[MACPLUMB]

You will want a hepa filter for that wet/dry vac. A standard filter will leak fine dust ! !

 

[4creation]

I would definitely make a shallow cut to outline what you want to take out. You definitely don't want to take a jack hammer to a floor and risk ruining the whole floor before you do that.

 

[98ZJUSMC]

I used a jackhammer on a similar project with a bathroom relocation (opposite side of plumbing wall) to put in a bedroom on my first floor. I used a fiber reinforced blade on a circular saw to cut a shallow cut along the outline of the whole excavation and then hammered out the slab (4"). No biggie. Low dust and the chunks came out quickly. The slab is reinforced. I rerouted my sewer pipe, connected up and was repouring the new crete about 4 hours after starting. Much easier than I thought it would be. Due to the slab not being reinforced, the big cutting saw may be the way to go so as to go easy on the rest of the slab. I almost rented a Hilti for that job.

 

[Ballvalve]

Who wants to run that gas beast in the basement? Any skil saw with a good blade and a hose makes no dust, just takes more time. 2 inches deep and a 5 foot piece of 2 or 3" iron bar and its out clean and cheap. Poke some holes to make the starter hole.

dont need a hepa filter cause there is no dust. TIME AND PRESSURE WINS ALL!

 

[Gator37]

Wet saw will help keep the dust under control.

 

[JCH]

Here's an update on what I've done and how it's worked so far.

Ended up using a (cam'd) hammer drill to drill about 40 (!) 1/4" holes approx. 1/4" apart around a corner of the desired opening. This was to give me a starting point. With a shop-vac beside the drill bit, dust wasn't an issue.

Then took a 8 lb. sledge hammer and gently (!) started tapping the concrete next to the drilled holes. Once the floor started turning to powder, I was home-free. It was just then a matter of undermining the existing edges (with a shop-vac) and then pulverizing the edge with the sledge.

I was able to keep a reasonably straight line with just using the sledge. No cracking of the slab. No drill holes needed (once I got started).

Here's a picture of it so far. Notice that I don't have any room to swing the sledge (nor fit a wet saw) under the concrete laundry basin.

In hindsight, I didn't need to drill so many holes. Next time would just drill enough to cover the width of the sledgehammer head. Total time for sledge work was under an hour. It was the excessive drilling that took all the time.

Question: Given that this is cast iron (heavy) and still in use, how aggressive should I be in tunneling under the pipe before the plumber arrives? He is going to install an underground wye--one to service the stack, and one for the basement laundry sink.

Would I be risking the weight of the stack shearing the underground lead/oakum joints??

Thanks for all your help so far.

 

[Jerome2877]

To fit 2 Y's you will need to make that hole bigger, then excavate under the pipe a good 3- 4" so the plumber can get his snap cutters around the pipe.

Those joints are very strong, you shouldn't have a problem.