One day, while driving, I had a thought about the radiant tubing I was going to be installing in these floors. See, normally, one drills a hole, in the joist and feeds the whole roll through that hole and then through the next until it’s in every joist and then pulls each loop that dangles through the joist cavity to the other end. Well, I didn’t fancy the drilling or pulling aspects and wondered if I could somehow avoid that pain.
My plan, as explained in the video below, was to route the top of the joists and install the tubing before the subfloor. Which I executed and it worked splendidly. I will say it was a pain to have to remember NOT to drive a nail through the tubing. If I did it again here are some guidelines I would use.
Do your layout design beforehand to tell you where to route the holes (which I did)
Mark your joists in one solid line on each end where the routes will be (which I didn’t do)
Your marks will tell you the pipes are X inches from the end of the floor, and you can make a corresponding mark on top of your floor to avoid nailing pipes.
Route a hole 1/4″ larger than your pipe size to let the pipe slide through the hole for adjustment when tacking up
Use staples to hold the pipe into the groove you cut
It was great to work with. Which means it stayed pretty flexible, I didn’t have any kinking issues, and yet still seemed durable. I’ve work with some stuff that kept kinking, or was impossible to bend, so this was a nice change.
Tubing layout is a whole post on it’s own, so I’ll just paraphrase. 1/2″ pex shouldn’t be run over 300 feet. The simple answer is by the time hot water has run through 300 feet of 1/2″ pipe it’s cold. If you have 600 square feet to heat, it has to be done in two 300 foot loops or circuits. In my case I had a 20 x 24 floor so I had 480 sq ft, which ended up being two 240 foot loops. I’ll tie these into a header later which is either a simple 3/4″ pipe with 1/2″ ports off of it, or a fancy one pre-built for being a header, with flow control etc.