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DIY Bathroom Remodeling: Phase 3

The Right Bathroom Backer Board

As Seen On
Cement Board like DuRock is the Preferred Substrate for Bathroom Walls

Probably the biggest fear anyone has with their bathroom is mold.

And rightfully so.

My wife has bad allergies & asthma, and any exposure to mold can trigger terrible respiratory reactions.

This in turn can land her in the emergency room.

Even if you don’t have asthma or allergies, mold is likely something you’d prefer to avoid.

In this tutorial we’ll share several bathroom renovation tips that can keep your bathroom’s air quality in tip top shape.

So keep reading to gain more insight.

What’s the Best Backer Board

One ofย the best options for bathroom walls & ceilings is cement board.

Cement doesn’t contain any organic matter for mold to use as a food source.

Cement boards are usually sandwiched between two layers of ย fiberglass mesh, so there is no paper in the product.

I personally prefer using DuRock NextGen made by USG. But not all stores carry it.

Here in the United States you can get DuRock at Lowes.

Cement Board like DuRock is the Preferred Substrate for Bathroom Walls

Keep in mind that cement board does require some type of waterproofing. RedGard is a great way to waterproof cement board.

You can also use Schluter KERDI-BOARD or Wedi instead of cement board.

Again there’s no paper for mold to consume. And these boards are easier to cut than cement board.

Most of the time I opt to buy Purple Board for the walls outside the shower.

Purple Board is a great option because its face is constructed from a mold & moisture resistant fiberglass mat.

National Gypsum is the manufacturer of Purple Board. It installs just like normal drywall and uses the same type of screws.

Purple Board is a Good Option for Bathroom Walls & Ceilings

So whether you’re installing bathroom walls or hiring a contractor, these are the best wall panel options to consider.

They’ll eliminate the odds of having mold inside stud walls.

But the avoidance of an unsafe bathroom environment doesn’t stop with just the backer boards.

 

What’s the Best Type of Drywall Joint Tapeย 

Installing cement board or purple board is very straight forward and is the first step in bathroom remodels.

The next move is to make these already strong surfaces one cohesive unit by using drywall joint tape and joint compound.

Joint tape needs to be used anywhere there’s a space between two consecutive bathroom wall or ceiling panels.

The picture below shows a great example of how purple board will look after it’s installed on the bathroom studs.

Bathroom Wall Installation Involves Using Joint Tape Where Two Wall Panels Meet

Even though this section is about drywall joint tape I want to point out that the purple board in the above photo is attached with coarse-thread drywall screws spaced every 8-10 inches apart.

If you have wood studs you’ll need to use coarse-thread drywall screws and if you have metal studs you need to use fine-thread drywall screws.

Since I mostly work with older homes I have a good supply of coarse-thread screws.

Use Coarse-Thread Drywall Screws when Attaching Drywall to Wood Studs

Okay, remember how we want to avoid paper in the bathroom since it’s like cheerios – a food source – for mold?

Joint tape comes in two different commonly used forms: paper or fiberglass.

If paper is bad for your bathroom wall panels then it’s not a good idea to use paper joint tape near the shower.

So this is why we used fiberglass drywall joint tape in Rob’s bathroom renovation (Rob is my brother-in-law, he’s a good guy who likes to make his own beer, which is awesome in so many ways!)

Use Fiberglass Drywall Joint Tape in Bathrooms to Avoid Mold Problems

There is no chance mold will ever grow on fiberglass.

And the other nice part is it has a sticky self adhesive back.

So you can attach it directly to the drywall (unlike paper tape).

I centered the fiberglass tape over all drywall panel seams.

Center the Fiberglass Drywall Tape Over All Seams

If you encounter a situation where there’s a wide gap (anything more than 1/4 of an inch) between two pieces of drywall you can fill the gap first with drywall compound.

Then, you can place the fiberglass drywall joint tape over the seam.

The picture below shows a section of drywall we installed to cover up the old mirror.

There’s a good 1/2 inch gap between the new drywall and old section of wall.

Fill Wide Gaps Between Drywall Panels with Joint Compound

I pre-filled this gap with joint compound then applied the fiberglass joint tape.

The drywall panels are in place. You have your fiberglass joint tape covering all the seams.

The fun part is next: using drywall joint compound!!

 

Pre-Mixed or Setting Type Joint Compound

There’s nothing wrong with using pre-mixed drywall joint compound.

It has the correct consistency and comes in a bucket that you can lug around anywhere.

But I remember watching a great bathroom remodeling segment on HGTV with Mike Holmes.

He had this tip:

The long setup time for pre-mixed joint compound makes it susceptible for organic material to embed itself into the compound.

He also went on to comment how he’s seen mold form on top of the compound in the bucket after it’s sat around for a few days.

Now this probably isn’t typical but job sites aren’t exactly the cleanest places.

Let’s say someone is eating lunch next to an open bucket of joint compound and Dorito crumbs fall in.

BAM!! There’s your organic food source.

Also, pre-mixed joint compound doesn’t harden rock solid like setting-type compound.

Setting-type joint compound comes in a powder that you have to mix with water.

The bags will have numbers on them to indicate the time (in minutes) it takes for the compound to harden. I usually buy the bag labeled “45”.

 

Setting Type Drywall Joint Compound

Setting Type compound also comes in bags labeled “20” and “90”.

This means the compound will harden in 20 minutes or 90 minutes.

If you’re new to using joint compound I recommend using the “45” or “90”.

But if you only have a small patch job the “20” comes in very handy. It will literally be firm enough after 30 minutes to apply a second coat.

Which leads me to another good reason to use setting type compound versus pre-mixed.

If you use “45” you’ll typically be able to finish a drywall project in a small bathroom in one day!!!

The first coat will dry within 45-60 minutes which will allow you to sand it smooth and apply a second coat within 2 hours.

If you use pre-mixed products they take considerably longer to dry.

I’ve waited a full 24 hours and sometimes the pre-mixed compound is still too wet to sand.

Now, all of this depends on the ambient temperature and humidity.

But I’ve switched to setting-type joint compounds and have been super happy with the performance & time savings.

What’s Next

Even if you’re hiring a contractor it’s still a good idea to become familiar with all the different types of building materials.

This will allow you to make the best decisions for yourself & your family when it comes to preserving the air quality of moisture prone spaces in your house.

We like cement board but if you’re waterproofing a shower don’t forget to research KERDI-BOARD and wedi. Both are fantastic backer boards.

If you’re doing a bathroom remodel and want to simplify the process register for the Bathroom Repair Tutor Video Library

We show how to build showers (Schluter, Wedi, Curbless, etc.), install tile, upgrade basement bathrooms, and more.

Plus you’ll get 30 days of support from us during your project – the extra guidance can be invaluable

Register Today

Cheers,

Jeff Patterson

 

 

 

27 Comments
  1. Rachel says:

    This post is GREAT! It answers a lot of questions I have about this topic. Thank you for another very informative post!

    1. Jeff says:

      Thank you Rachel for your comments. I’m really happy that it helped you ๐Ÿ™‚

  2. Great tips on remodeling. This was some really good information. i will definitely pass this information along to my clients. Thanks for sharing.

    1. Jeff says:

      I’m happy the post was helpful. It makes me truly happy to know that others can benefit from the projects I’ve done ๐Ÿ™‚

  3. Great tutorial. I like a lot of what I am seeing here. I’m in the process of remodeling my parents bathroom for accessibility as they grow older as they have chosen to stay in their home till they pass. There is a lot of work I didn’t know about before I started and this blog has been a great help in keeping me going strong, Thanks!

    1. Your parents sound like mine Roger. They’ve been in the same house for over 40 years and aren’t looking to move.

      Thanks for making my day and I’m glad that you’ve discovered some ideas that will be helpful. Please add any tips you learn, I’m always looking pickup something new myself.

  4. Mary says:

    Hey Jeff! I just bought a house I am renovating, and I am glad I came across your site! I am about to start my bathroom renovation, and this post will definitely help. I had one question though… what size coarse-thread drywall screw do I need to purchase?

    1. I like using 2 1/2 inch long screws Mary because they tend to bite better. When you think about it, the drywall is 1/2 inch thick. So that leaves two inches to hold the wall to the studs. Of course, some people like to add construction adhesive to the studs for extra hold. But I tend to avoid this just because it can get messy.

      Plus there’s a little voice in the back of my head questioning what will happen if I want to replace the drywall down the road and if the adhesive will cause more issues than it’s worth. Anyhow, I can’t wait to see your renovation. Make sure to send me some pics ๐Ÿ™‚

  5. Grant says:

    Very helpful!! Thanks for taking the time to put this out there. You answered many of the questions I had, as a first timer remodeling my bathroom.

    1. You’re super welcome Grant. Let me know if you’ve got any more questions. I’m a first timer, too when it comes to a lot of things. For some reason though, I love remodeling bathrooms and trying to fix them when they break.

      ๐Ÿ™‚

  6. elay says:

    thanks so much

    1. You’re super welcome Elay. Hope the tutorial helped ๐Ÿ™‚

  7. Jacinta says:

    I am glad that I found your blog. I currently live in a condo unit where we have had some issues with mold in wet places so now that I’ll be moving into my own home soon, your info is invaluable. Its always good to have the info you need, even when hiring out. Thanks again, great post.

    1. Thanks so much Jacinta. Congrats on your home purchase!!! I’d be happy to help you with any questions.

      Man, I’m pumped that you’ll be moving into your own place. Way cool.

  8. zina says:

    Hi Jeff! This is a great post. When my contractor re-did the shower, it looks very sloppy where the tile meets the ceiling (about an inch), I was thinking I might put PVC trim or quarter round to finish it off. But I like a clean modern look and worry it’ll look bad. Any suggestions?

    1. You know what Zina, have you thought about adding glass mosaic tile? This could look really cool and most tiles are about 1 inch. Or you could add a 1 inch sliver of the existing tile.

      I wonder why the contractor left the gap?

  9. Robert says:

    Great piece! But I have one question. What do you use to fill the gap between the wall board and a fiberglass shower stall? Do you use joint compound or do you use grout?

    1. If I’m picturing this correctly Robert you should use silicone caulk.

      Buy caulk that’s specifically for bathrooms and has Microban in it.

      How’s your remodel going? I’d love to see pictures.

  10. Jee says:

    Hi Jeff. Great stuff. What a feeling when you find someone who is saying what you need to hear. I’m somewhat confused about moisture barrier requirements. First, there is nothing between the cement board and the studs, right? (Except shims as needed) And secondly, is the cement board to be coated with RedGard? Or just the transition between cement board and wallboard. Thanks.

  11. pat lynard says:

    I think it’s better to call a professional. It’s how they make a living.

  12. Mel says:

    This was so helpful at understanding the basics. My next question is what about flooring. I am using plastic laminate flooring for my bathroom. Should I have special flooring under to ensure no mold gets in or is that enough?

  13. Dan M says:

    I suggest adding a suggestion for using drywall shims to correct inconsistencies in the studs both vertically and horizontally before installing concrete board. Otherwise your concrete board may not be flat even if it’s installed correctly.

  14. Carlyle says:

    I just bought an old Colonial house with an unfinished bathroom and this tutorial answered many questions. Thank you very much.

  15. My says:

    Have you ever used the Hardie backer board for the shower walls?

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