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Radiant Floor Heat

One of the projects that I worked on since we bought our latest house is in-floor heating in both bathrooms (tile) and in the kitchen (crawl space on wood).


We renovated both of our bathrooms and decided to put in tile floors. Tile floor is great in the summer time, it stays nice and cool which helps to battle our 30 degree C or more temperatures. However the tile floor feels even colder in the winter. So to help with this I decided to put in-floor heating. This is not an overly complicated task, especially if you are going to use electric heat. For a couple hundred dollars you can get everything you need from Home Depot.


There were some other changes I wanted to make the same time when redoing the floor. I needed to move the toilet to accomodate the larger tub as well as a couple other things. I also didn't want the toe kick when you walk into the bathroom. So the only option was to lower the floor to make room for the tile height. So to do this I cut the floor out and poured cement to lay the tiles on.


So here are some pictures of me pulling out the floor the sub floor. You can also see some pictures from the old tub. I am a slow worker, you can see we were still using the tub as construction was going on.

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In these next pictures you can see that I am also pulling out the shiplap so I can frame it for cement.

I didn't cut the shiplap out right up to the wall, the walls are sitting on the shiplap (this would be bad). So the areas that still have shiplap won't have heat, but it worked out well because in all cases it is in places that you wouldn't normally walk. On last few photos you can see that I scabbed on 2X4 planks about 2" down from the top of the floor joist.

So now that I have the floor out and the scabbing done. By the way the cement and all of the weight above the cement is restting on the scabbed planks, so secure them well. On these next photos you can see that I have put in the plywood onto the scabbed planks. Again you will want to secure them fairly well. When the cement is wet all of the weight rests on this plywood. Once the cement has cured the plywood does nothing or very little. In these picture it is a little easier to see what is going to be cement and what will not.

So I now have to get the pipes in place for the floor heat. I am using a hot water system to heat the floor. This is a little tricky and should really be setup by a professional. If you are going to do this yourself you need to be smart about it. If the water that circulates through the system remains stagnant in the pipes for any lenght of time it can and will turn skunky. So you will fill the tub to have a nice bath and the water will be a little green. This is dangerous and I strongly recommend putting in a closed system. More on that later...


Anyhow, in these picture you can see that I drilled the holes through the floor joists for the pipe and started to lay it down. Installing the pipe like this really is a pain in the ass. There are easier ways, do some reading on installing pex.

In the above pictures you can see that I have snugged the pex right up against the floor joists. In the first floor that I did I left some space between the pipes and floor joist. This made a cold line down the floor right above the floor joist. So by attaching the pipe right against the floor joist it starts heating the wood right away and minimizes this cold line. It actually worked really well...


I took pictures before I put the rhino board down so I knew where the pipes are in cause I run into any problems and I need to open things up. Fortunately that hasn't happened. In the last four pictures below you can see that there is a piece of wood attached to the top of the floor joist. This is to create a void on the top of the joist after the cement is cures and the wood strip is removed.

Well as you can see I finally got to pour the cement. I know a guy who knows a guy and got the cement for free. He even put some of the mesh in so that I didn't have put reinforcing mesh or rebar into the cement. This makes things so much easier and quicker. Talk to your local cement people about this product. It looks like straw in 2 to 3" lengths, it turns the cement into a fiberglass like product.


After the cement was dry then I removed the strips of wood from the top of the joists. I have done this so I can screw the rhino board to the floor joists. I will fill these voids with versal bond or some other type of thinset. This same product will be using that to laminate the rhino board to the cement / wood. The way I have attached the rhino board (cement board) to the shiplap is not ideal. But I took a chance and so far not one cracked tile. Once again I have only done this is very low traffic areas.

We are getting close to the end. So I don't have any pictures of spreading the thinset and laying down the cement board this is fairly easy. Just use a notched trowel just like installing tile, make sure it is well buttered so that the cement board doesn't have any air pockets underneath. Of course you will want to cut the rhino board and dry fit before you do anything. So now you have the board cut, thinset down and now you lay down the cement board and screw it down. I used rust resistent screws, not sure if you need to but I had to buy something anyhow, the extra five bucks isn't going to break me. As you will notice I screwed down to the floor joists (using long screws) and I also screwed down to the shiplap (short screws) just to firm things up and make sure nothing flexes.


One last little tip about this step, when I spread thinset on the shiplap I used masking tape to stop the thinset from falling through the cracks and messing up my clothes washer in the basement.

So as planned things have worked out perfectly. My floor is about a 1/2 inche lower than my hardwood floor. So once the tile is installed it will be the correct height. No toe kick.


My kitchen was a little different task. I need to run pipe through floor joists and attach it to the underside of the flooring. There are many different ways to do this. The easiest is probably a metal reflector plate to attach the pipe to the underside of the floor. You can also use staples. I was in a crawl space and didn't want to be swinging a hammer so I used some strong tie down straps and my narrow crown stapler. This was easy, fast and holds like a damn. Thank you Dan for all of your help crawling around under my house.



I am going to call this project done.


  • I should have put something on the plywood before pouring the cement, you want your cement to dry as slowly as possible so that it cures properly. The wood pulls the moisture out. Sealing the wood with something would work well. Also make sure that you don't turn on the floor heat for at least three weeks, ideally 27 days.
  • I used 1/2" plywod to pour the cement on, 3/8" would probably be fine or thicker. It just needs to support the weight until the cement has partially cured. Do the math on how much your cement will weigh.
  • Make sure you mark your joists and pex line crossings so you don't put a screw through the pipe.
  • Wear a mask when cutting the rhino board, it is pretty nasty stuff.



Click here to read more about radiant systems. This is a great resource.


I have discussed the actual heating system on another page.

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