Busting up slab in basement for bathroom piping...

I have a house a few years old and am looking to do the basement. I want a full bathroom in it, but in the location of this bathroom all I have is a clean out stub coming out of the floor. It's the final cleanout in the entire line, next to the wall that goes outside and to the street.

It seems that for all my stuff I can either bust out the concrete floor (I've been reading about it) or build up above this stub for a completely raised bathroom and put a Y above that stub leaving one end accessible and then everything hooked to the other.

A few questions:

1) Other than the manual labor involved are there any big gotchas in concrete slab busting? For example is it possible that instead of pipes surrounded by gravel with a concrete top layer the builder unfortunately wrapped a lot of the pipe with concrete? This could make tapping into that line extremely hard.

2) Is it "taking a shortcut" if I raise the floor and don't bother hacking into the slab? Given that my main sewer is below the slab and I don't need a macerating toilet, ought I certainly to go with the bust-slab approach?

 

is there 'any' chance of having 'post tension' reinforcement in the basement floor?

 

What do you mean, the metal posts that support the I-beam in the middle of the house? There are two. The closest one in this case would be about 12 feet away from this trench. I have no idea what's in the concrete like rebar or whatever else.

I just read about this. Apparently some wires are stretched, then the concrete is poured and let set, then they are relieved, which has the effect of pulling it all together under continual force. I have no idea if this was used.

 

I have extreme doubts there are any tension cables in your basement, that type of construction is only used for commercial applications. I think that you should break up the concrete because of the loss of head room if you raise the floor. It should not take long to break down where your pipe goes and determine exactually whats there, your call.

 

I am certainly leaning in that direction. What is the worst mistake a newbie could make with this? I am going to read up on it quite a bit but if I did something really dumb (other than cutting a body part) is it possible to destroy what's down there to some huge degree? I plan on circular saw to score it then a rented electrical jack hammer and a chisel and hammer around the pipes to be a little more gentle...

 

Skoorb,

I've actually just completed doing the same thing in my basement. I found it to be easier than I expected. I rented a 14" circular saw to cut the edges of the hole and then a jackhammer to break up the concrete and remove it. I got both of these from Home Depot.

Initially I chose not to rent the diamond blade for the saw, which was a mistake. The fiber blades don't cut well and don't last very long. I also originally decided not to rent the large jackhammer, which made things very difficult. Go with the large jackhammer, the ones in my Home Depot were green and came on a small two wheeled hand truck.

To give you an idea of what you will find under the floor, my slab was about 4" thick. There was no re-bar or reinforcing wires. Under that was about 2" of gravel, a plastic sheet, then about 6" more gravel before finally hitting the clay (which is what all the ground around here is made of).

A last word of caution... The circular saw will create a HUGE amount of dust. I put up some plastic sheets to prevent the dust from travelling throughout the whole house. Make sure you have some kind of ventillation and you wear a dust mask, safety glasses and hearing protection!

 

From an old thread I remember post-tensioned slabs are very common in TX and the southwest...but they are normally used for slab foundations..not basements I don't think.

I seriously doubt theres any chance of it in residential work in NY.

A little off topic..but thought I'd throw it out.


Oh and to avoid the dust..which can haunt you long after the work is done. Just close off the whole are with dropclothes somehow and use a wetsaw..or at least trickle water on the cut. The water and slurry will be easier to cleanup than the dust going everywhere.

 

Thanks for continued ideas. I'm leaning strongly in this way now.

I've read some tips for reducing dust include the one just mentioned to trickle water toward the blade (and the person said even a regular saw this can be done, just avoid getting electricuted--I have no idea if that is actually safe or not), but also:

1) Have somebody else with a shop vac sucking up constantly as you cut
2) You can get some large furnace filters, tape one to the back of a large fan and have this blowing away from your work area, it will suck the air through the filter and help grab some. One person who took this advice in the thread said it was really good advice.

another quick question

Assuming I have those black pipes under my slab running water (I actually believe I do not have them for some reason, despite neighbors having them; I don't see an inlet into my sump from one), is it a huge deal if I cut into one? I suppose I'll have to fix it up.

 

Skoorb,

I assume that the black pipes you are talking about are the plastic drain pipes that carry water to the sump. It would not be a huge deal if you accidently cut into one of those. You can just patch it up. That pipe is pretty inexpensive so it wouldn't even cost you much.

 

Yep, that's the one. Is it a similar non-issue if I manage to cut through the vapor barrier? I presume I have a layer of plastic or something under the slab...

 

You shouldn't be cutting deep enough to get to the vapor barrier -- there should be a couple inches of gravel or base between it andd the concrete. If you DO hit the vapor barrier, you're cutting too deep.

 

Or the builder screwed up We'll find out which one, should it happen

 

Well, yeah, THAT'S been known to happen!!

Repairing it is pretty easy -- duct tape!!

It's not a slit or two in the vapar barrier would cause the house to fall down, or any other damage for that matter.

 

Newb question: How do I get the measurements for this done up? I have read a few books and guides about this. I plan on having 2X6 stud wet wall against my foundation walls and it will sit on a lip of concrete left untouched by this but despite having a basic layout in mind of my bathroom (5.5X8.5' I think) exactly how do I space the toilet and bathtub for plumbing?

How standard are dimensions of toilets; i.e. the toilet drain is precisely 12", for example, from the wall in 99% of toilets? Do I really need to buy the tub, toilet, and sink first and then lay them out on some cardboard to make a template or something along those lines? For obvious reasons I need to know before doing the final piping and having it set in stone--concrete

 

The toilet dimension of 12in from the FINSH wall to the center of the rough-in is close to standard. You must lay it out with at least 15in minimum on both sides away from the edge of anything

The tub you have to know exactly what you are installing, those measurments are taken off the rough wall, once you rough it in the slab put a box around it, about 8x12 inches for clearance when you hook it up.

Your sink you can run into the wall close to where the sink will be, don't run it dead center, you can finish the rough-in when you decide what you are putting there.

Your toilet and tub will have to be dead on, luck.

 

Thanks, shacko. It sounds like I may want to pretty much buy or at least find the specific model (and ensure it's common enough that it won't go away before I buy it?) of the tub and maybe sink before I start busting...

 

For the dust on a concrete diamond blade I always have another person stand nearby and use a hand-held yard sprayer full of water to help kill the dust. If you use an electric saw then too much water could be a bad thing. If it's gas powered then water won't be a danger to the operator. Even with that the dust will be ridiculously messy. Good luck trying to contain it.

You shouldn't have to cut the entire footprint of the bathroom up. I did mine about 4 years ago and I just cut 14" wide sections out of the concrete along the routes the piping would need to be installed. You could cut much narrower sections if you know how deep that line you are connecting to is. I would suggest removing that clean out and trying to get an idea how deep that line is. If it's 6 inches below slab then an 8" wide access would work, if it's deeper a wider one might be needed.

I wanted it large enough I could dig down along side the pipe and cut sections out so I didn't disturb the actual ground the pipe was sitting on. I didn't want to have to worry about getting the pitch right again because I didn't know how close the level it was initially installed.

If you wanna cut the whole footprint up then have at it but it is a lot of extra work.

 

Standard tubs are usually 60" long by 32" deep, with the nailing flange about another 1 1/4". So the center of your tub drain will be about 16" off of framing. You are supposed to have a minimum of 15" from the center of the stool flange to anything beside it like the tub, cabinet or wall. So if your tub is the above mentioned the center of the toilet must be atleast 47" off of framing.

When doing the underground for the tub drain it's way easier to leave about a 10"x12" box around the area of the drain. Fill it with dirt and set the top of the box at finished floor level and leave concrete out of course. One side of the box should be flush with the drain/valve side of the wall and centered on 16" off framing from the back. Then during rough in set the tub in the hole and level it up. Measure from the back wall to the center of you're drain. Pull the tub back out and set you're p-trap underground by digging enough dirt out and hooking on to the drain pipe you left(during the underground just stub a 2" pipe anywhere under the box and duck tape the end). I use a 2x1 1/2" bell and an 1 1/2 glue p-trap.

 

Use a different tape than duct tape (with life of 4 years and not waterproof) like a Tyvek or even foil tape. Better yet, sticky window tape. Otherwise the ground water running under your slab by capillary action will find the slit and go to the warmer and pressure different concrete slab, and surface as a wet spot for you. Right through your finish floor covering, even tile. Right after you poured a new concrete patch! Especially water on a clay stratus..... Be safe, Gary

 

Thanks, guys! I did find that tubs are really not standard in this manner, so I will go with the approach of finishing all the plumbing save for a large hole for the tub and once I get the actual tub in place finalize it.

I had forgotten about the overflow stack, but in the case of that it looks like the best thing to do is leave a super-high 2" stub and then just cut to height when I need to, and there is enough room in front of the average tub to wiggle around a little bit if I'm off an inch or so left and right.

I've seen in lowes/HD a drain & overflow kit, but it requires room under the tub, so makes more sense for an upper level. Otherwise I'd have to raise the tub a few inches on top of a platform, which isn't the end of the world but if I could get it sitting right on the floor I'd prefer it (and I presume it's the way a good plumber would do it).

 

Some tubs are "above ground rough in" and some are not. Either way that is what the shower box is for. You have a section of concrete under the tub drain and overflow that is void so the pipe can actually be ran under the floor level. Usually you need atleast 12" from the valve wall. I would use a watco drain/overflow kit. Along with that you'd need a 1 1/2" pvc tee and glue p-trap. I've done this in probably over a hundered basement baths. Just leave a 2" horizontal pipe close to the bottom of the concrete but NOT in the concrete. Glue a bell reducer on and set your p-trap. The overflow will drain into the top of the tee and the drain elbow into the branch. The bottom of the tee drains into the p-trap.

 

Well I'm in. The concrete is about 3" thick laid immediately on top of vapor barrier, then all the rest of the gravel, so I've had to completely remove the vapor barrier, but I bought some new 6 mil so it's ok

If I had to do this again I would splurge and rent that proper cutting saw from home depot. The circular saw route spoken about in basement books is not good. It was impossible to control the cracks and much of the bathroom has cracked up to the foundation wall and had to be taken out, so I have a lot of concrete I have to pour back now! 30 square feet or so :O

I completely understand what sdplumber is talking about now, too; going to glue everything up soon and hopefully pour in the concrete next weekend (so that I can start in the morning).