Raised/false floors for plumbing

I was just checking over the new Willow Feeder page and was reminded of something. Due to the nature of having a bucket under your seat, they both have raised floors or steps.

We built a small community house last year that included 2 bathrooms. The original design was pretty standard with all the plumbing & pipes buried in the floor. We found this pretty bad because we kept making small changes to the design & layout as we learned more about our needs, as we built. But if all your stuff is in the floor, you can't ever get to it again! Heck, if it starts leaking after a year, how would you even know? There's a toilet sitting on top of flooring on top of a subfloor. Sometimes interior walls are sitting on the subfloor, so you'd have to bust out a saw to even check. Or you put trap doors everywhere for checking lol. I suppose this is why people have crawlspaces.

But the obvious answer for us was, why not just build a slightly raised floor instead, and put all the pipes in there? I suppose it could be "less stylish" and confusing to a normal home owner, but I see no downside to having to step up 1 or 2 steps to get into the bathroom, or onto the toilet/shower. Then you can have all your plumbing above floor level, easily accessible, easy to check on, easy to fix.

We are planning on doing this once we put a full shower in the second bathroom.

Anybody have experiences with or thoughts on this?

Sure it's all been done. A couple of my oilfield skid shack houses had raised plumbing floors. Been done in remodels as well. Also prevents freezing in an obviously movable structure.
The door is a bit of an issue, on top of raised floor or in front of raised floor? You'd want/need a landing outside of the door to prevent someone stumbling out and down at the same time in the dark through the door.
If you are not building on a slab, then your floor should have had a ventilated crawl space under it for sure. I'm guessing you also have no building inspectors involved or yours is pretty low.
There are no leaks....... right? Why pressurized piping is always continuous in inaccessible spaces. ABS drains will never leak in your lifetime.
Water supply can also come from overhead, then only drains are affected.
Another issue is the rigidity, false floors tend to be kinda weak sounding/feeling. Subfloor glue helps, under framing and holding subfloor down to framing.

Usually all the plumbing is in the walls.  Why put plumbing in a raised floor?

Anne Miller wrote:Usually all the plumbing is in the walls.  Why put plumbing in a raised floor?

Toilet drains go down.
Always. Pretty sure. Basements were not part of OPs question.
Only your upstairs neighbor has a toilet drain passing through your wall. Vents, of course, always rise through a wall. In wall one way vent caps can be used where a riser is not practical.

In places that never freeze, most plumbing could be in an exterior wall. Carving a drain line through a wall stud doesn't leave much framing meat for stiffness. Plumbing tends to be in 2x6 walls. Walls can be doubled or furred out for additional room. Soffits can be added to conceal overhead horizontal pipes.
Codes have requirements, based on common sense, and experience about the length of in wall laterals for drains and number of turns allowed, and the requirement for cleanouts.

Standard toilets do flush down.
Most commercial toilets go into the wall.
These use pressure instead of gravity ,to flush.
They require a large supply line, like 1" or bigger.
There are probably exceptions to this, toilets that add pressure some other way.
If not, a pump could be rigged to do this.

Or, a crawl space could be used.
Gravity is very reliable.
I live in Cincinnati, where basements are the the default, at least in the city proper.
I used to think no house should be built without a basement.
Now I think that preventing settling is the most important foundation issue.

Settling foundations will break plumbing lines, no matter what kind of foundation it is.
I think lines coming up vertically into the middle of a foundation might be more resilient than any that come in the side of a foundation.

William Bronson wrote: Standard toilets do flush down.
Most commercial toilets go into the wall.

Do they then stay in the wall?? Or do they then also go down at some point?

Commercial units go horizontal for a very brief run into a wet wall, where they also go....
Down.
Pretty sure.
Built more than a few commercial buildings.
Either way, the problem is the same. If you stubbed your plumbing up through a floor or slab, and then change your mind......
Hammer up a slab or open a subfloor.

Yes of course they go down, it's just a question of where.

By keeping the vertical part of plumbing out from under your toilet and bathroom in general, you get different options for designing your building.
By keeping your plumbing runs in a wall chase you can access them without a sledge or jackhammer.

At work I am often entering large utility chases, and even though the space is tight, its much better than the crawlspaces I've been in.
They are usually multistory, with expanded metal flooring on each level.
I can imagine a central utility room acting as a big walk in chase, with laundry, bathing , toilet and kitchen clustered around it, in single family house.
Add your furnace and electrical panel , land line and Internet and basically you have an above ground basement, so what's the point?
Well basements are expensive, that's the point.
What if instead of the adding the other utilities to the first floor utility room, we add stairs to a utility attic?
Only the plumbing needs to be run through the foundation, everything else can probably go upstairs.
This mimics some of the commercial buildings I'm familiar with, with most of their HVAC equipment in their penthouse instead of in a basement.

+1 For the central utility chase/closet idea.
Add a chimney for the RMH, folks plan for chimneys after the fact often as well. Keep the heat in the center of the house, instead of giving half to an outside wall exposure.

Yea that sounds amazing. Toilet is really the only thing in a normal residential setup that currently "has" to go down. Hence my false floor idea. Obviously if you could remove that you don't even need the false floor! I love the idea of the utility room, we actually sort of already did that in the house I mentioned. All the plumbing & much of the electric in one wall accessible via a hinged door from the storage room. Only thing you really can't get to from there is the toilet..

I've lived in/visited many homes in Canada that used the 'raised platform' approach to plumbing.

1. Usually, there was a separate raised platform for each "item", so one for the toilet, and one for the tub/shower combo. If the bathroom was in a room on a slab (basement in the two recent examples I experienced), many people don't feel good about digging into their slab for many good reasons.

2. Look up, look way, way, UP! If you're old enough to remember that line. You can build a platform to solve the plumbing trap location and gravity issues, but every inch you go up, reduces the headroom. So you need to keep that in mind.

3. Safety: Having a bunch of floors at different levels is a safety issue. It's much easier to trip or bang a corner, or forget you have to step down. If as per Point 2, you have lots of head room to use, I would vote for obvious steps up to the bathroom with a secure handrail, and then have the whole bathroom on a single level. However, that's simply not always possible.

4. Accessibility: steps into a washroom, and even a platform for the toilet, may make the toilet "inaccessible" to many disabilities, even temporary ones. It's amazing how quickly my friends saw the downsides to their house arrangement when one of them broke her lower leg in 3 places! Her husband was amazingly helpful and supportive, as he learned all about commode chairs! So if you're renovating already, I *really* recommend you look at quality grab bars and information on recommended locations. They do *not* have to look industrial. I have seem beautiful stair rails, and grab bars are close relatives. If it's not a public building, they don't need to qualify as 'public requirements' - just do as good a job as that plain metal tube does!

5. I totally agree, even in my relatively benign climate, keeping every pipe you can on a internal wall! Keeping them close to each other saves time/costs/energy. Knowing where they go in a wall, and how much insulation they are protected by, gives peace of mind, particularly if you get a power problem along with cold weather!

6. No matter what the end plan is, making pipes accessible without taking the whole house apart is always a good plan. For some reason, plumbers are very prone to messing up the bath tub connection, as I know several houses where that was an ongoing problem... sigh...  However, recently a friend had something go wrong in the wall behind her toilet, and getting in there to fix it was a chore and a half. I'm not sure there was any way to truly improve that access due to space constraints, but do the best you can. I know so many toilets that are badly boxed in to save every inch of space, so I do understand that sometimes it's just not possible.

Here in Florida a majority of building has the supply and drain plumbing immortalized in the concrete slab.

This is a terrible idea because the pressurized supply side will often develop a leak that's very near impossible to locate and  would require breaking a lot of concrete to fix, if you could find it.
There was a lot of copper tubing in that era that was defective and one ex plumber friend told me that any dings or dents in copper water line will eventually cause a fail at that point.

Ii had a house where this happened and I ended up running the supply plumbing through the attic crawl space after wasting money on a service that claimed to be able to find the leak and couldn't.

My other thought was to put it in the ground next to the slab and tap into it through the exterior wall.

I was able to ask some plumbers about this and they all suggested overhead due to that being easier to hook up to by dropping lines down through the wall and cutting a "hatch" in the drywall to have room to make the connections.as opposed to breaking holes in the exterior walls, which were concrete block.

Better for frost issues too.

Yea it seems that concrete slab somehow draws people in cause it "sounds solid" or something, but it has TONS of drawbacks..

Apparently, concrete doesn't even last! Mike Oehler says the average concrete structure lasts about 30-40 years before the concrete has to be replaced. There are timberframe houses in Europe that are 500-1000 years old!

Yeah, quality control has been going down the drain for a while.
Cutting the cement percentage in ready mix concrete is a cheat that usually won't be detected until decades later.

The old cracker houses here are up on stone pilings and built from first growth pine centuries ago .
Many survive today.
If that old pine catches fire it's all over quickly though. That stuff burns like gasoline.

I believe up on pilings is the way to go.

It's not uncommon to see all feed lines mounted on the interior walls of a Nordic house. If we are just talking sewage lines the entire floor wouldn't have to be raised just a platform for the throne, tub, sink? Some point with a slab foundation there is going to have to be a penetration somewhere, unless you are going through an exterior wall? That might be a nightmare trying to connect all waste lines going to a central collection point. Macerating up-flush toilet?

M Pearson wrote:Yea it seems that concrete slab somehow draws people in cause it "sounds solid" or something, but it has TONS of drawbacks.

I'm building an alternative house, using clay, sand, and foam glass. No poured concrete at all.

I first excavated my foundation. For my climate, it was 18" deep. Then, I put EPDM rubber over that. Then, I put the plumbing in, with standpipes approximately where the fixtures would later go.

I then filled the excavation with foamed recycled glass. It has an R-value of 2.4 per inch, so it will be like eight inches of fiberglass.

Over that will go a bit of sand for levelling, PEX tubing for a heated floor, then a poured earthen floor of about 2".

If I ever really need to get at the plumbing, I can dig through the floor. It won't be simple or easy or cheap, but it will be doable, unlike if it's in a concrete slab.

One thing I always wondered...

When a grocery store is built on a slab, trenches are cast into the slab to run the refrigerant lines from the compressors in the back out to the coolers and freezers in the store.

When the refrigerant lines are laid in the trenches they're suspended in sand.

The whole thing is topped with a thin layer of concrete that's easily broken through if access is needed.

Seems a possible for residential if you weren't in a cost/time hurry like most contractors and had to go with a slab?


This little tidbit came from my days running my scrap metal businesses.

There was a guy who bought all the equipment from closed grocery stores who would give me all the scrap in exchange for pulling all the different units that he could resell off the roof with my crane.
This had to be done carefully because the roofs were rubber membranes and you don't want to rip or damage that.


His copper salvage trick was to cut the copper line at the compressor on one end and the cooler or freezer on the other.
He would then tie it off to his fork lift and pull it from the compressor side.

As long as you had a fairly straight pull you could easily pull all that copper tubing right out of it's little sand burrow.
There's a LOT of copper there.

Hello from northwest Florida! I have experience with using raised floor and I will share my experience with you. I bought an old farmhouse in a rural area of northwest FL in 2021 because I could buy it without a mortgage and since I'm retired living on social security I want to keep my long term monthly debt obligations at a minimum. This house was built in 1939. The wood framed house is built with wood foundation resting on old brick piers but 87 years of water and soil has made the crawl space inaccessible. The previous owner used it as a storage shed and had gutted the kitchen and bathroom, there was no inside plumbing left inside the building and I wasn't interested in what might be under the house. The roof had leaked at one point; they had stripped off the ceiling tiles in the bathroom area leaving the staples and remnants of the ceiling tiles behind on the tongue and groove ceiling boards. That is another story I may share later if anyone is interested in what I did to cover that without having to pull out all the staples. The point of this reply is to share my experience with you about raising the floor to accommodate plumbing drain lines. After I purchased the property I located the septic just outside the old gutted out bathroom and had it inspected by licensed professional. Although it was original 1939 style septic system built using bricks it didn't need pumping out and it was in great shape. I was told that no one had lived in the house for about 30 years. I decided since I couldn't get under the house, nor did I want to, that I would just build a raised platform inside the bathroom and run a 4" drain pipe using proper plumbing code fall above and along the existing subfloor exiting out the wall to a new 4" air vent pipe up the side of the house as well as drop down and tie into the septic pipe which is cast iron that I cut with a Sawzall and used a rubber connection made for that purpose to attach to the cast iron. My platform is 10" tall, and I use a 7" step to get up onto the platform. As for the water pipe plumbing, I had a plumbing company install a new 3/4" pvc pipe from water meter at the road and bring it up at the front corner of my house. From there I did the rest, I put a shut off valve, that I built a shelter around and insulated, and ran it inside the front of house above the floor above the baseboard to use that area as a pipe chase. I ran that pipe above of the 6" baseboard all the way along the inside of house above the baseboard to the back of the house where the bathroom is. I am still in the process of covering the pipe chase with a bench seat that will have access doors and I think will look nice and be very handy. My plumbing drains and incoming cold water is inside my house, it is accessible and doesn't freeze or get too hot. Where I live it reaches over 100F during summer with 80% humidity, and has been down to 10F in winter. We had 10" of snow a couple years ago which is unheard of here but with this crazy weather nowadays who knows what will be normal in the future.  I have also ran other plumbing fresh water and drains inside the house for sinks and the washing machine that do not connect to the toilet drain, they are mostly  2"  inside except where sink is 1-1/2" that I adapt up to the 2" that connect outside at a higher point on the 4" air vent because even with the proper 1/4" per foot fall they connect higher than toilet and they can could never have a toilet water backup into household fixtures.  I am in the process of building a shower now and it also has a dedicated 2" drain that goes outside to the 4" vent stack similar to the sink drains.  One more worthy mention is air venting inside the house, follow code as to how far from vent fixture is, it is easy enough to add an air vent pipe and run it outside. I never go through the roof, I go up outside wall. I enjoyed sharing my experience with you, and afterall that is what you asked for. Happy Remodeling! Cheers!