Rerouting Drain pipes in concrete slab: DIY or call a pro?

[Andy Ring]

I am a fairly accomplished DIY plumber, but all my previous projects have been on bathrooms and kitchens where the plumbing was accessible from beneath and in wood framing. Now, I'm contemplating renovating a bathroom that is on a concrete slab (not a basement, however). The toilet and shower locations will be swapped, so I will need to redo all the DWV lines for these fixtures which are in or under the concrete slab.

Soo...with that intro, is this something I can do myself? If so, what would you recommend? A wetsaw? A rotary hammer? Any advice would be appreciated. I think the slab is fairly thin, but it's hard to tell. Drain lines are PVC. If this wasn't in concrete, I'd have no problems...

Thanks!

[Bob NH]

If you want to work with what you own, and it is no more than about 3" thick with no steel; you can get masonry cutoff wheels that will fit your skil-saw. Make a groove about 3/8" deep where you want to break the concrete (both sides of trench); then attack it with a sledge hammer. Don't try to work in less than a foot wide.

It makes a lot of dust, but you can try to keep it wetted down. You should have a dust mask.

When it comes to restoring the concrete, I like to mix my own. The SackCrete is always short on sand and cement and it makes for a poor surface. One sack of Type 1 Portland cement, plus GOOD sand and gravel, will make about 5 cubic feet of concrete, which is at least 600 pounds of SackCrete (number of sacks depending on what HD is selling at the moment).

[johnapril]

Ladies and Gentlemen,

Thank you for being such a rich resource of information. This is my first post. I would like to piggy-back on the subject.

I am considering transforming an existing outdoor porch into an indoor space. I want to turn half of it into a master bathroom and the other half into a laundry room/sitting area. The house is built on a crawl space. The porch is built on a 24' x 8 ' slab (about 4" thick; not sure whether it's steel reinforced). I would like to know your opinions about which way to go, the pros and cons, of the following two options:

1) Plumb through the slab, connecting into the plumbing in the crawlspace

2) Break out the slab, dig crawlspace, plumb through the new crawlspace into the old. [Does anyone have any idea about the cost of such an option?]

Every sort of thanks!

[Bob NH]

I don't fully understand the picture of your two options.

What is the level of the new floor relative to the crawl space? If there is clearance, and it is possible to make the necessary connections to the mains, you might be able to run the piping in a new crawl space. It would have to be protected from freezing, but you are already doing that with your existing living area.

Since the slab is only 8 ft wide, I would take it all out rather than try to cut through in places for plumbing. A man with a decent backhoe and bucket could probably load it on a 5 ton truck in an hour and you could start from a clean slate.

[johnapril]

I don't fully understand the picture of your two options.

What is the level of the new floor relative to the crawl space? If there is clearance, and it is possible to make the necessary connections to the mains, you might be able to run the piping in a new crawl space. It would have to be protected from freezing, but you are already doing that with your existing living area.

Since the slab is only 8 ft wide, I would take it all out rather than try to cut through in places for plumbing. A man with a decent backhoe and bucket could probably load it on a 5 ton truck in an hour and you could start from a clean slate.

Bob,

That is what I think I needed to know. The slab is at the same level as the subfloor over the crawlspace. But if the job of removing the slab wouldn't take that long, then it might be worth it to start from a clean slate.

So, in the clean slate scenario, how would I then connect the new plumbing to the existing plumbing in the crawlspace? Do I dig trenches in the earth, bore a hole in the wall entering the crawlspace, run the pipes through, then pour a new slab over all this? Or is it better to match a new crawlspace to the existing one?

Thanks again,

John

[Bob NH]

Your questions can only be answered by someone who can see the details on the site. There is just too much information to consider, and we don't even have all of the information.

[hj]

Assuming the slab is installed correctly, there are two considerations.
1. It should have a slope to it to provide drainage.
2. It probably does not have a footing around it, so anything built on it could suffer from ground movement.
3. take it out and provide a proper foundation for the addition.

[johnapril]

Thanks, all. This will help me when speaking with my contractor.