Plumbing Freeze Protection in Exterior Wall
Plumbing Freeze Protection in Exterior Wall
Just failed my rough plumbing inspection for water lines in an exterior wall in the garage. The garage is framed 2×6 with Zip sheathing on the outside. We are in climate zone 5 and the garage floor has hydronic/radiant heat.
The inspector cited IRC P2603.5 and suggested bringing the pipes out to the face of the 2×6, framing essentially a double wall. My biggest issue is that he was not specific in any of this. He mentioned no measured distance from the sheathing, R-value for insulation, etc. It was very arbitrary, although I understand his concern. He also called out the frost free hose bib I had installed as too short, but again without any specific length/requirement.
My issue is making sure that whatever I do to address this is both a solution that I am happy with, and one that the inspector will find acceptable after putting in all the effort to redo this.
The wall has an internal hot/cold hose bib, a sink, a shower for the dogs, and an exterior hose bib.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Dustin,
The IRC says in P2603.5:
"A water, soil or waste pipe shall not be installed outside of a building, in exterior walls, in attics or crawl spaces, or in any other place subjected to freezing temperature unless adequate provision is made to protect it from freezing by insulation or heat or both."
It is "arbitrary" in that it doesn't dictate exact requirements. It's a performance standard. You have to show the pipes won't freeze - and what you do has to be accepted by the inspector.
The two sure-fire solutions I can see are to move the plumbing out to a service cavity on the interior of the wall, or move the lines close to the interior face of the wall and fill the cavity outside them with foam board.
Arbitrary is exactly the problem. When you mention "close to the interior face of the wall," they are already within an inch of the face of the 2x6 studs. I could notch the holes that they are currently in, pull the pipes up against nail plates, and foam in the holes behind them. That would bring them an inch forward.
I think ultimately I need to figure out a solution and then call the senior plumbing inspector to make sure he will stand by whatever I come up with, before I go through all the trouble and hours of labor to address this.
I was sort of hoping to be able to go to him with some sort of evidence to support whatever solution I come up with. It just seems wrong to me to meet the 'standard' of good enough as long as they are further away from the sheathing than where they currently are. I was really hoping he would have some measurement of distance/R-value of insulation to design for - or a reputable example that I could take to him.
In my opinion it's always a mistake to route pipes in exterior walls. What would you do if the exterior wall were solid and couldn't take pipes? Does the sink have a cabinet? Then the pipes should come out of the floor and go through the toe-kick and up. Does the shower have walls? Then the pipes should run through one of the interior walls.
I know it's frustrating to fail an inspection but the inspector is helping you out here. It would be very frustrating to have to tear out all the finished work to thaw the pipes.
It's in a garage, and the slab is poured. I understand now those solutions are ideal, but I'm trying to work within constraints of existing construction, not spend 100 hours of labor and thousands of dollars in materials to start from scratch.
Dustin,
We have a similar type of provision in our code about where the vapour barrier in walls needs to be that reads "The vapour barrier shall be installed sufficiently close to the warm side of the insulation to prevent condensation at design conditions."
I think the proof they are looking for to show the pipes are safe from freezing is as simple as adding 3" of polyiso foam board behind them (R-18), and making sure there is no insulation except the drywall (R-0.5) on the interior.
"He also called out the frost free hose bib I had installed as too short, but again without any specific length/requirement."
The end of the fixture has to be in the conditioned space. So you need an 8" or longer fixture for a 2x6 wall. If the wall is finished you have to deal with a pipe coming out of the wall. I would run it through the wall and into the cabinet for the sink. You're going to need a shutoff on the inside anyway and under the sink is a good spot for it.
These things fail all the time, you don't want to bury them anyway. If you put on a tail of a couple inches of copper or PEX and connect to the supply with a Sharkbite, when it's time to replace it it's an easy job to separate the Sharkbite and you can just pull the fixture out and swap it. Depending on how much space you have it might even work just to have a Sharkbite ball valve.