Interior shower plumbing located on an outside wall

capejohnNovember 2, 2009

Does anyone have shower plumbing on an outside wall? We are located in North Eastern Massachusetts. Our plans call for the valve and shower head to be located on an outside wall.... and I'm wondering if that will be problematic (freezing up). We have 2x6 framing and will insulate the walls with R19 fiberglass. So does anyone have anything similar... any problems? Thanks.

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I'm not too far from you and my shower head has been on an outside wall since 1903 with no sign of damage. It's buried in vermiculite plaster and is placed entirely horizontally so it can drain after use. In new construction I would put closed-cell foam between it and the outside sheathing with nothing on the warm side. The shower mixing valve and any vertical piping should be on an inside wall.

    Bookmark   November 2, 2009 at 9:22PM
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Plumbing Codes everywhere require plumbing supply and drain pipes subject to freezing to be insulated, heated, or both.

Shower and bath valves located on an exterior insulated wall can work, but locating shower or bath fixtures on an exterior wall does nothing to comply with other plumbing codes that require the shower valves and slip joints to be accessible for repair and replacement.

Unless you wish to cut a minimum 12" by 12" or larger access panel in the exterior siding of your house to get to the shower/bath mixing valve and drains...

Locating a shower/bath valve, risers and drains on an exterior wall is simply foolish and should be avoided at all costs.

    Bookmark   November 2, 2009 at 10:47PM
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He didn't ask about a drain and there is no code requirement for access to the supply pipes.

    Bookmark   November 3, 2009 at 6:57AM
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Hmmm, builder told me we couldn't run waste lines from upstairs down an exterior wall, we had to frame an 8" wall at the end of the kitchen cabinet run. But our washing machine supplies and drains are on an exterior wall - and the plans were reviewed and stamped, the building inspector never questioned it, plumber never said anything. We're in CT, have 2x6 framing with R22.

    Bookmark   November 3, 2009 at 7:05AM
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This is more info than you asked for, but it's all related...I am located about 20 miles north of you. Generally speaking, you should avoid plumbing supply lines in exterior walls. For a shower it is even more important because you want easy access to the valve if something goes wrong. We positioned all our shower valves so they were accessible from a closet (so damage would be easy to repair). If that isn't possible consider what is on the other side of the wall and how easy it will be to repair. Drywall, easy. Custom wainscot, not easy. I would redesign that shower.

Re: other interior plumbing, the pipes for sinks generally come up through the floor, so they are techically inside the house. However, some people like the wall mounted kitchen sinks, and that can pose a problem in colder climates. For our laundry room we insulated the 6" wall and then build another 4" or 6" wall inside that. The plumbing for the washing machine is inside the inside wall.

And yes, this does all make a difference. We have had an issue with the toilet supply for our master bath freezing (happens when it is below 5 degrees). I looked through the many photos we took during construction and saw that the plumber put that line in the garage ceiling (same as the other master bath supply lines, the garage is heated) as close to the exterior wall as it would go without actually being in the exterior wall. Not sure why he did that (the toilet is on an inside wall, no reason to run the supply where he did). All the other lines are fine, they are further from the exterior wall. We will eventually take down a section of the garage ceiling to fix this.

Also, for a few $100 more you can upgrade to R21 insulation. I know it's only 2R, but it doesn't cost much.

    Bookmark   November 3, 2009 at 9:30AM
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Just make sure they run the lines as close to the inside of the wall as possible to allow the most amount of insulation behind it. The sower valve has to be placed where it needs to be according to your stall type, but the lines themselves can be placed as far to the inside as possible. Im assuming 2x6 exterior walls here. The lines will be protected from screws or nails when sheetrocking with the use of nail guards.

    Bookmark   November 3, 2009 at 10:15AM
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The only reason to put a shower head directly above a shower mixing valve is to avoid the work of running a pipe horizontally through studs. I always offset the valve from the head in a shower stall.

The only shower mixing valve I've ever had to replace was over 100 years old. There was a rebuild kit still available but I couldn't get one of the nuts loose. If you're concerned about having to replace the valve get a better quality unit.

    Bookmark   November 3, 2009 at 10:23AM
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We're in WI, and we're going to have a shower head on an exterior wall. Our builder wasn't crazy about the idea but bc of the shower configuration, we didn't have much of a choice. He is building out that wall, and basically putting a second interior wall in front of the exterior wall and putting the shower head on that. So, it's like a 2x4 framed interior wall right on top of the 2x6 interior wall, both insulated. May be it's overkill, but I guess it makes him and us feel better.

    Bookmark   November 3, 2009 at 10:33AM
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It is important to not put insulation on the interior (warm) side of the pipes. The use of rigid foam board will double the insulation value on the exterior (cold) side of the pipe.

    Bookmark   November 3, 2009 at 4:25PM
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We built a house in Westchester county New York three years ago and we have a shower on the outside wall.

The shower is in the corner and has two outside walls. One wall is where the pipes are which are filled with water (duh, will explain in a bit). That wall houses the valve control, and all taps for the shower. That wall has special double insulation and intrudes into the room a bit, say 4 extra inches or so to accomodate the extra insulation.

The other outside wall of the corner shower is the standard thickness and has standard insulation. We have some shower sprays there. Note however that the lowest shower head is at the bottom of the pipes, therefore those pipes remain empty of water when not in use, i.e. when you are taking a shower there is water them. When you trun the shower off the water drains out and the pipes are empty.

So far we have had no issues.

Warmest regards, Mike.

    Bookmark   November 4, 2009 at 6:09AM
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"He didn't ask about a drain and there is no code requirement for access to the supply pipes."

There most absolutely IS a Code requirement to access supply and rain pipes if slip joint or compression type fittings are used.

And those are the types used most commonly in these applications....

So WHERE is the Code required access to the drains and shower valve going to be?

Through the exterior siding?

HOW will the owner repair/replace the shower mixing valve in the future when it fails if the entire assembly is placed on an exterior wall without any access?

The things architects are supposed to think about...yet never do...and make everyone else go HMMMMM.....

    Bookmark   November 9, 2009 at 10:18PM
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I’m sure it’s possible to think up a shower mixing valve installation that would require an access panel using something like union couplings but I’m also sure the OP’s plumber is capable of avoiding such unnecessary amateurish connections and thereby be able to avoid an access panel. The same is true for the drain trap although that doesn’t seem to be an issue for this project.

If you want to know the right way to install a shower mixing valve, get one of those step-by-step books with the color photos and if you want to advise a homeowner in Massachusetts about plumbing code issues, read the Massachusetts Fuel Gas and Plumbing Code.

I’m sure your insults about architects are meant to hurt my feelings but I find it entertaining to see you fall on your face when pretending to know more than people with more training and experience. Keep it up. And give me more CAPS, I love CAPS.

    Bookmark   November 10, 2009 at 4:10PM
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collins design

I haven't read the whole thread but I just want to say, "don't do it!"

We moved into a house last fall with a master BR/bath addition built in 1990. They had code inspections (we saw it on file at the town office) so it must have been to code then at least!
The supply plumbing is in the 2x6 exterior walls. There is just normal fiberglass batt insulation there. We live in southern coastal Maine, so about the same climate as you. Last winter (our first here) a neighbor stopped by one day when it was forecast to get down in the single digits. "You'd better run your faucet tonight in that bathroom!" he advised, "otherwise the pipes'll freeze!" Sure enough, not only the pipes froze, but the shower drain (it's on a crawl space) did too. We didn't realize it till spring, but the drain broke enough to leak, and when it started warming up we discovered that it had created a HUGE mold issue. We subsequently had to gut the entire thing, even the floor. We are now re-routing the supply lines through the attic, and building insulated boxes around the drain traps. So- be careful. Every contractor who looked at this shook their head and said, "I can't believe they ran the supply in the exterior walls!".

    Bookmark   November 10, 2009 at 4:35PM
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There is a right way and a wrong way to put a shower head on an exterior wall. Don't blame the plumber; blame your house designer.

Remember that what keeps the pipes from freezing is the heat in the house so the shower door must be left open, there should be no insulation on the warm side of the pipe, the cavity should be sealed against exterior air infiltration and the insulation behind the pipes should have about twice the R value of a normal wall. In your case the insulation should have been at least 4 inches of polystyrene foam board, or better yet, 4 inches of sprayed closed-cell polyurethane foam which takes care of air leaks that can defeat any amount of insulation.

But the best method is to allow the shower head to drain after use and put the mixer on an interior wall.

Running pipes in an unconditioned vented attic or crawl space is not usually a good idea. The temperature of the ground would keep pipes from freezing if the crawl space was insulated and air sealed but that is sometimes difficult to achieve if it wasn't part of the original design. An insulated box that extends to the uninsulated surface of the ground might work if properly air sealed.

Pipes in an unconditioned attic can work if heat is allowed to rise into the insulated pipe space.

Avoid slip joints or compression couplings in any location.

    Bookmark   November 11, 2009 at 8:05AM
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Unfortunately macv designs and speaks 'as if' Massashusettes Code is the rule rather than the exception.

Most US states use the IRC Plumbing provisions and less so the UPC.

That said, my 'gripe' with macv's advice is from practical experience after nearly 30 years of building.

Designers never have to 'think' beyond the point of getting their plans paid for by a potential owner nor approved by the local code official.

After that they have no liability and no culpability if their plan just stinks.

Planning a shower with controls on an exterior wall is absurd and is never done by any designer with any common sense or serious building experience.

Not only does placing a shower with controls on an exterior wall create future replacement and repair issues, it creates immediate freezing issues for plumbing that do not need to be there.

It is easy for a designer to 'think' he has it 'right' when he refuses to consult with the builders or code officals...has no actual hands-on personal building experience...and is isolated in his office at his desk making up things that may or may not exist all day.

That is what makes claims by 'architects' so comical when people like me...who review architect designed plans for code compliance for a living...can usually pass about 2 plans in 10 because architects just have no clue.

Designers and architects are not typically the solution..they are typically the problem...

And why consultations with your builder and code officials even more important than conversation with your designer.

So don't be fooled.

I'm not...and will continue to challenge 'non-sense' passed off as 'good sense' by some designers here...who really have little idea of what they speak...and are happy to be recognized for that ignorance....

    Bookmark   November 11, 2009 at 10:54PM
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It is painfully obvious that everything you know about building a building comes from a code book or a code class and that you attempt to disguise that fact by berating and insulting those with greater knowledge and experience, especially those who are licensed professionals.

I’m sure it is difficult for you to maintain a superiority complex while checking the work of licensed professionals using a book of rules based on a lower standard, so you need to feed it by coming to the GardenWeb and spewing self-righteous absolutes in ALL CAPS about building codes and evil architects like a Bible thumping evangelist.

Lately, you have been trying to draw me out by making disparaging personal remarks about my abilities and experience but I'm only going to tell you what you have probably already realized: you don't have the training or experience to understand how wrong you are about me in particular and the construction of buildings in general and I have no desire to help you.

    Bookmark   November 12, 2009 at 2:20AM
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The shower head in our bath was on an exterior wall, even though the "exterior" was the garage. We also have 2x6 framing with blown-in cellulose. Code in our area (IL) required an additional 2x4 "wall", so the total width of the exterior wall was 10" in the shower area.

Now, for some reason, code didn't require the hot/cold water lines on the exterior wall to the Laundry to have a built up wall? Go figure

    Bookmark   November 12, 2009 at 5:02PM
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I'm not a plumber, but I'm married to one. Maybe it "can" go on an outside wall, maybe not, but I know that it is a really bad idea.

I also know that Code is not best practice. Code is not so much about reliability, either, it is mostly about safety.

A number of years back, not too far from op, a really high profile, big price tag subdivision went in with many of these outside wall setups. Profitable for the local plumbers and carpenters the first few winters. Probably profitable again for the carpenters, too, some 20 years down the road when the valves fail...

And of course they will. Everything mechanical fails sooner or later. Given all the many variables--what direction the wall faces (north worst, for example), water hardness, type & quantity of insulation, nearby windows, doors, thermal bridging from studs, etc., etc. and all the hooey you'd have to go through to optimize the setup as much as possible (extra walls, extra insulation and special insulation installation, etc.) why bother?

    Bookmark   November 13, 2009 at 8:44AM
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"I also know that Code is not best practice. Code is not so much about reliability, either, it is mostly about safety."

I couldn't have said it any better. No matter what the code is, the "best practice" in the area the OP is in is to avoid supply lines in exterior walls and to build a double wall where it can't be avoided. I have ONE instance of a supply line in an exterior wall (it actually isn't IN the wall, but it right next to it, in a heated garage) and it freezes when it gets below 5 degrees. I am very glad we used PEX.

    Bookmark   November 13, 2009 at 11:03AM
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The building code for 1 & 2 family dwellings is mostly prescriptive which means it actually sets minimum and maximum values and sizes structural members for a given location in the house. This is not intended to be used as a design guide but to place limits on what you might design yourself.

Using the code as a design guide can result in deficiencies but that is not the fault of the code writers. The joist size tables do not consider long span bounce. The wall systems described are the ones most commonly used but the code does not intend to forbid the use of others. The waterproofing requirements are not extensive or adequate although the addition of the requirement to install materials according to the manufacturer's instructions was intended to fill that gap. Concrete foundations and slabs should be designed to ACI 332 since the IRC does not consider many common detailing problems.

Placing pipes in an outside wall is a design problem that may be addressed by some codes but there is no reason to prohibit that condition. If there were to be a restriction it would have to be based on a map or list of locations similar to the requirements for wall vapor retarders.

You can base your decision about the location of pipes on anecdotal information and other people's opinions or you can design the wall to avoid freezing of the pipe. If you choose the latter, you can use the formula normally used to locate the dew point in a wall in order to determine where the temperature would be 32 degrees or lower.

Ignoring air infiltration for a moment, a water supply pipe 1 1/2" deep in a 2x4 stud wall and insulated with 3 1/2" of fiberglass insulation would probably freeze at about -10 degrees F. Ironically, removing 1 1/2" of the insulation on the warm side would lower the outside temperature needed to freeze the pipe to about -50 degrees but for fiberglass insulation air-infiltrations makes that prediction unreliable.

So the design solution is to air seal the stud cavity and place R-10 or greater insulation on the cold side of the pipe. This is best done with spray foam (Icynene, etc.) and if the studs are 2x6's, the R value would be as much as R-14 which would put the temperature of the pipe at about 55 degrees when the outside air temperature is -30 degrees F. At that outside temperature the house temperature would need to drop below 45 degrees for the pipe to freeze. This design is roughly equivalent to a double 2x4 stud wall with no insulation in the interior wall and 3 1/2" foam or dense-pack cellulose insulation in the outer wall.

The way it was done in my house back in 1903, was to put a "double wall" of wood lath and rough plaster at the middle of the full 2x4 stud cavity throughout the house and at the shower pipe the space behind the pipe was filled with vermiculite plaster. This pipe has never frozen but because of the risk of air infiltration I don't count on protection below -20 degrees.

Remember that these calculations assume that the interior temperature is 68 degrees or higher, so if you set the thermostat at 55 degrees or the bathroom is under heated or you close the shower door you should adjust the calculation.

    Bookmark   November 13, 2009 at 4:59PM
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Digging up the dead here but we want to have wall mounted faucets in our new build's master bathroom.

The wall is an exterior facing wall.

Our builder says he will need to 'furr' out the wall.
I googled it but couldn't get the an answer that I could understand.

But does furring out a wall means adding another wall in front of the exterior wall (really towards the inside of the house)?
Does it mean adding insulation to the front of the exterior wall & then building another wall in front of that?

    Bookmark   August 13, 2012 at 2:29PM
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What your builder is saying is that he will make the wall thicker to allow more insulation to be added hence keeping the pipes nice and cosy. This may lead to a reduciton in floor space, and / or an intrusion into your bathroom. If well designed this can be made seamless and looking good.

The risk you run is if you have a freeze and the pipes burst. Sort of depends on where your house is and the local climate.

The word "Furring" come froms the term for Furring Strips. These are pieces of wood which are nailedonto your wall studs to make the wall ticker.

Best, Mike.

    Bookmark   August 13, 2012 at 2:50PM
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Thank you stinkytiger aka Mike!

We are planning to lose about 6-12 inches but the worry is still the freeze possibility.

While we technically live in the South (Middle VA) - w/40's most winters, one bad winter could really ruin everything.

    Bookmark   August 13, 2012 at 2:59PM
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Hi Pbx2,

I have a wall like that and I am in New York, Westchester county. There are some tricks to this. Since it is a master, you may want to have one of those multi-head showers and lots of jets etc.

I have the shower on a corner of my home. You can have pipes which you know will be empty before and after the shower on a wall without the extra thickness. I.E. you know water will drain out after the shower. So those pipes are always empty once you are done. So I have one wall which is thicker, and one wall which is thinner / standard thickness.

The other tricks may be to use more plastic pipeing for those lines. Plastic has more give than copper. The other thing is to have perhaps an extra shutoff valve in your basement / utility area for those water lines. So if you have a break, the damage is (a) easy to contain, and (b) you can run the rest of the house as usual. The extra cost of two extra water values should not be too high.

Best, Mike.

    Bookmark   August 13, 2012 at 3:21PM
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Not fully comprehending what you mean by:
You can have pipes which you know will be empty before and after the shower on a wall without the extra thickness.

Can you explain your thought process please.

Our exterior wall will actually hosue 2 sets of wall mounted faucets for our his+hers vanities.

Since they each will against an exterior facing wall, we will run your experiences past my builder:
1) Plastic piping for flexibility
2) Extra shutoff valve for exterior wall water lines

    Bookmark   August 13, 2012 at 4:37PM
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Hi Pbx2,

My shower is in the corner of my house. I have two outside walls forming a L shape. I have five jets in the shower.

On the thick wall I have the temp control, jet control, overhead shower head, and shower head on a flexible hose. At any point in time, there most likely will be water present which can freeze. Hence all this stuff is in the thick wall.

On the other L part of the wall, the thin wall, I have three shower heads. The lowest of which is perhaps knee height. The knee height jet is the lowest item on all the plumbing and drains out into the shower. When the shower is on the water is warm and sprays onto you. When the shower is off all the pipes in the thin wall become empty. Any water ther drains via the knee jet into the shower. Therefore there is no water to freeze.

Best, Mike.

    Bookmark   August 13, 2012 at 4:46PM
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