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05-21-2019, 07:21 AM
My wife would like a new bathroom. We live in an old barn in Maine. I converted the barn to a house 30 years ago. The kids have been gone for awhile and now seems like the right time as the snow is gone. The room in question is on the first floor. There is a crawl space under this that can be damp in the spring. The building has a full foundation. The room currently has 2x8 joists on 16 inch centers. The span is 9 feet. It currently has 3/4 inch T&G Advantec for the floor. The room is nice and empty and she has a plan. All I have to do is find a way to get this done. This seems like the perfect place to get some good advice. I am considering using 1/4 inch CBU then tile over the subfloor. I have done some tile work on a few floors and counters but not in a bathroom. I could use some advice on whether the subfloor as it sits is adequate or needs replacement or adjustment before starting the tiling. Also, she would like one of the rectangular drains on one side of the shower unit. I have done a lot of regular plumbing in my life but not one of these in a shower so could use a little advice on this. I have leveled a floor before but not created something that is a little out of level so this is a little counter intuitive to me. If anyone has insight about this type of project I would really appreciate your thoughts. Thanks, Jack

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05-21-2019, 08:04 AM
Welcome, Jack. :)

Not much for our people to go on there. You say "The room is nice and empty and she has a plan," but you don't give us any hints as to what that plan might be. I'm guessing you plan to have a shower in the new bathroom, but you don't indicate such. And will it have a tub, or just a walk-in shower? I'm further guessing there will be a WC somewhere in the room.

Tiling the floor can be as simple as you indicate. If your joist structure is as described (you need to know the unsupported span of the joists, not the span under the floor to be tiled), your subfloor structure meets the minimum requirements of all the tile substrate manufacturers I'm aware of, so the CBU and tile should work.

'Bout as far as I can go with the information at hand. You might visit our Liberry and find the Shower construction section in there. Some useful information in that thread and may prompt more specific questions on your part.

My opinion; worth price charged.

05-21-2019, 08:45 AM
In addition to what CX mentioned, I'd recommend encapsulating that crawlspace if it sees a decent amount of moisture (can be done with foamboard, thick plastic vapor barrier, spray foam, and an investment of time and back pain) to prevent the weakening of your subfloor you plan on tiling over.

05-21-2019, 11:30 AM
Thank you for your thoughts cx. I do have a lot more information as I built the barn 30 years ago when I had a lot more energy. Actually, rebuilt a 200 year old post and beam framed barn would be more correct. The open span of the 2x8, 16 inch OC joists is 9' 1" as I recall. This will be a full bathroom with a walk in shower, WC and sink. While I know how to set tile on CBU, I was getting a little dizzy from trying to find information on what would make a suitable subfloor. In the end, I would like for this to be a very nice job that lasts as long as I will without leaking or needing repair. I have found that there are more ways to do waterproofing now so that seems like a great advancement for keeping the water in the bathroom. I think that the plan is about as normal as you can get. The door is on one wall, the sink on the left was as you walk into the room. The WC is on the right and the shower will be straight ahead. It is on an outside wall. That particular wall is pretty thick. The outside wall was installed with 2x6 studs and faced fiberglass insulation. About 10 years ago when the kids started leaving, I went around all the outside walls and added an interior wall of 2x4's with fiberglass insulation. I also put up osb on all my walls before putting up the sheetrock. So the results were that we started burning a lot less wood. It also made the walls pretty thick so had to trim out all the windows again. My wife thought it was just great but that kind of finish work always seems to take forever for me.

My comment about the room being nice and empty was simply that the room is actually empty. I had to remove all the wall covering to re-run the electrics so they would be in the right place for the vanity/sink and the light for the mirror. I did put in a new exhaust fan with a light so had to tear out part of the ceiling. I just decided to go the whole way and put back the green sheetrock which I found our is now purple. (Been awhile since I built our last bathroom). I was prepared to remove the floor and replace it if folks that knew more than me thought that would be a better answer. The floor has been there for quite a while. I wondered if taking it up, gluing the advantec down and then putting a few more screws when I put it down would help. Not sure most folks up our way were gluing the floors when this was installed. I will say that the floor is not dead level. It does slope a little toward the middle of the building. I was going to use that pitch to my advantage if possible by using a rectangular/side drain for the shower. I don't have much pitch and have not actually measured it for the 1/4 inch per foot but water poured on the floor does run toward where I am planning the drain. If I wanted a little more pitch, is there a reasonable way to increase the pitch, just a little, inside the shower unit?

I will check out the shower section.

Radas, thanks for your thoughts. I have thought about doing that project for about 30 years. I would think it needs doing but it sure is a lot of work. It might just be OK to try this just a room at a time. Sort of limit the back pain part to manageable bites.

Just so everyone knows, it is really nice to be able to talk with someone about a project like this. I have been blessed over the years to have some great teachers but none of them were tile folks.


05-21-2019, 12:33 PM
Jack, some of that information, 'specially the parts about "up our way" and such, would be a good bit more meaningful if you'd add a geographic location to your User Profile. Helps in answering some types of questions.

While your floor tile doesn't give a damn whether your floor is level, it does care about it being flat. The larger the tile, the more it cares.

I'm guessing you're talking about using a linear shower drain, and, therefore, a direct bonded waterproofing membrane for your shower receptor. While this can be a good plan, without at least a drawing of your floor plan it's difficult to determine how this might work for you and where you would install the drain. Doing it all without cutting into the subfloor (and optimally the joists) is going to limit your placement options without requiring your to raise the level of the entire bathroom floor a good bit.

Removing all that old (and possibly moisture damaged?) subflooring might be a useful step in flattening your subfloor and adapting it to the shower floor you're trying to install.

The more information you can provide, the better our folks are likely to be able to help with the project.

My opinion; worth price charged.

05-22-2019, 05:50 AM
Thanks for getting me started in the right direction. I will update my user location. We are in the northwest part of central Maine for what that is worth. Lots of winter most years.

I will post a plan for the bathroom. When I was still working I was a mechanical engineer so after a lifetime of building and working on equipment as well as fixing all manner of things I work pretty much from a thorough sketch. I have that but it is at home. My wife and I are traveling until near the weekend. I will get it posted when I get back to the house.

You suggested that I read the threads on building bathroom showers. I did notice in one of the many threads that you mentioned that using CBU as a floor for a shower was not OK. At least that was what you seemed to say. I could have read it wrong as my eyes were getting a little crossed by that time. Would you comment on that specific issue? I think at the end of the process I am just trying to get the floor right and then select the best method for creating the floor of the shower so it will not leak.

Sometimes I learn slowly but I do make every effort to learn.

Thanks again,
Jack Harrill

05-22-2019, 08:27 AM
Let's be honest here, Jack. Do youins Mainaics have any season other than winter most years? :D

Whatever you're reading is probably giving you some correct information. I know of no industry accepted method of shower construction that uses a CBU to construct the receptor floor.

There are a number of ways to construct a waterproof shower receptor. The traditional method, in use for many, many decades, involves a sloped floor, usually made of deck mud, shaped to a two or three-piece clamping drain, over which is placed a PVC or CPE membrane clamped into the drain and turned up the walls around the perimeter and over a raised curb at the shower entry. Over this membrane a second mud bed of consistent thickness is placed for the ceramic tiles to be bonded. The shower walls are made with a different kind of mortar or with a CBU over a moisture barrier that laps over the receptor membrane. That method is still in wide use and still functions quite effectively.

The more modern approach is to make a similarly sloped floor, or use a pre-fabricated foam tray, but ending at a drain that has a wide flange designed to be bonded to a Direct Bonded Waterproofing Membrane (ANSI A118.10) that is then continued across the receptor floor and up the shower walls above the shower head, making a completely waterproof container to which ceramic tile can be directly bonded.

There are variations, of course, but those are the two basic approaches in use today. You will hear argument in favor of each, and you'll decide which is most attractive to your particular application.

Using deck mud to create the sloped portion of the shower receptor makes it simple to build over floors that are not perfectly flat or level as is the requirement for the prefabricated foam trays. The mud also allows you to make the shower floor fit the shower footprint and drain location perfectly while having a level perimeter that makes tiling easier and more attractive.

My opinion; worth price charged.