Do I Need To Use Redgard Over Hardibacker?

Use Redgard Over Hardibacker

Note: As an amazon associate I may earn a small commission from qualifying purchases if you click to amazon from my site and choose to make a purchase.You can read my complete affiliate disclosure for more details

Do I Need To Use Redgard Over Hardibacker?

Regard is a water-based paint that you can apply to walls, ceilings, and other flat surfaces.

It has high adhesion qualities, which means it will stick to any surface without peeling or cracking.

Once the paint dries, it’s tough enough to resist stains from most common household substances such as alcohols, oil paints, gums, and inks.

This makes it perfect for DIY projects in your home. But, Do I Need To Use Redgard Over Hardibacker? 

No, You don’t need to apply Redgard over your Hardibacker. Here’s why: Redgard works best on cement boards and plywood because it prevents water from seeping into those surfaces. It can also work on top of drywall that isn’t behind a tub or shower, but it will eventually wear off after repeated moisture exposure.

It would be best if you never used Regard on wood-based products like particleboard/MDF, oriented strand board (OSB), medium-density fiberboard (MDF), pressed wood/veneer ply.

One of the best uses of Redgard is when you’re installing a new bathtub. It’s a good idea to apply a thin coat to the backside of your tub before you install it.

If water gets behind the tile, it’s more challenging to seep into the cement board with Redgard applied.

Is It Necessary To Waterproof Hardibacker?

Yes. You will need to add waterproofing material on top of the Hardibacker before applying any tile or stone.

This is because Hardibacker is for applications where you cover the product with tile, absorbing water.

If you don’t waterproof your Hardibacker, then any liquid (water or otherwise) that accumulates on top of the board may saturate into it and cause issues with mold, mildew, rot, etc.

Before installing Hardibacker, read its instructions for details about proper installation preparation.

You should also fully understand how to use a trowel when applying thin-set mortar to ensure that you’re using the right amount of adhesive for the job.

Can You Tile Directly Over The Hardibacker Board?

Yes, you can tile directly over the Hardibacker board.

Many shower pan contractors prefer installation over Hardibacker as it makes the surface even and gives a consistent substrate for their pans.

Since Hardiebacker is ceramic-bonded instead of cement-based.

It should have similar results to any other ceramic or porcelain tile that’s installed on a backer board such as Durock or Wonderboard.

There are virtually no installation issues with tiling directly over Hardiebacker. However, there are a couple of things you need to watch out for:

Make sure you remove all thin-set from behind the backer board when finishing your wall surfaces.

This is to ensure that you don’t get any staining because of the adhesive seeping up through the grout.

You may need special thin-set mortar to adhere the tiles to the backer board, such as a modified thin-set ;

Or tile adhesive especially made for adhering on surfaces such as Ditraset or Mapei’s Ultracolor Plus.

Do You Put A Thin-Set Under Hardibacker?

No!It would be best if you put it over Hardibacker. It would be best if you put a thin-set over Hardibacker, not under it.

This protects your pipes from being accidentally punctured by the screws used to secure the boards to the wall studs.

If you lay it on top of the Hardibacker, then there will be no way for them to come into contact with your pipe.

Even if you have to attach it at an angle because of a corner or something similar.

If you do not think it’s essential to protect the pipes from puncture, lay thin-set over Hardibacker because it makes for a better surface.

The used screws will hold the boards in very well. Thus there’s no need to worry about them moving or coming loose.

If you put thin-set under, you risk anything sticking out below, catching on your subfloor, and popping up. Lay it all out first before setting anything into place.

After trying this method, I found that laying everything out first only wasted time putting down more sheets than necessary because of poor measuring.

I suggest you put your thin-set down in the places where it will go, don’t lay everything out first.

Use Redgard Over Hardibacker

You can measure each board to ensure they are all roughly the same length but try not to fuss over it too much because if you make a mistake with one piece.

Then there’s no point trying to correct it later when you have already set in place all the others.

A good example would be if I were in my bathroom laying tile around where the showerhead is (sitting on top of a wall);

And just found out that it needs to be slightly moved more over than I had initially thought, so tiles don’t cover up that part of it.

If I had measured everything before setting it into place, then I would have to pull those tiles up and move the showerhead;

Making me go through the hassle of chiseling out some of the thin-set that has already been set.

Can You Apply Redgard With A Brush?

Yes, You can apply RedGard with a brush. However, it would be best to first make some minor adjustments to the mixing and application process.

It’s important to note that though RedGard will go on with a brush, it may not adhere as readily or evenly as if sprayed.

For this reason, I don’t recommend applying with a brush; instead, I suggest using our airless sprayer for best results.

If you still wish to apply with a brush (convenient for hard-to-reach areas), do the following:

  • Use 3 gallons 10M01B RedGard Activator diluted in 20 gallons water (for every 100 square feet) instead of 4 gallons 5M13S RedGard diluted in 20 gallons water.
  • Add ¼ ounce 10M20B RedGard Thinner per gallon of the mixed product instead of 1 ounce 5M13S RedGard Thinner per gallon of mixed product.
  • Apply with a brush or roller specifically designed for this application (not a standard painting brush).
  • Use only clean water in your container to mix your diluted activator and thinner – no soap, detergent, or anything else.

This will eliminate any potential for reactions with the paint and primer you are applying over the top of it.

Is It Necessary To Tape Seams On Hardibacker?

Yes. It would be best if you were taping your seams when you install Hardibacker.

It would be even better if you taped them before installing the board entirely, but this is not at all necessary.

The reason that Taper Lock Tape (Tape-Lock) or Vinyl Backer Rod is usually used with backer board products like HardiBacker and Durock.

This is to improve the sealing of joints so that no water can seep in between the backer board and the substrate it’s installed on.

Excess moisture trapped behind either of these two types of board can also cause mold growth.

Which will compromise the strength of your building material, so keeping seams tight with tape helps prevent this problem.

Walls less than 1/4 inch thick don’t require tape because the backer board has sufficient structural integrity to hold up without it.

You should only tap your seams if you use Hardibacker or one of its competitors, not drywall.

While these two types of building materials serve different purposes, they are both cement-based board products that work together as a firm foundation for your walls.

But keep in mind that you can’t tape seams on drywall either – you have to miter them. If this gets confusing, think of it this way:

You wouldn’t build a house out of HardiBacker by itself but alongside drywall partitions.

The same goes for using regular old 1/2″ drywall instead of something like Durock. As a result, you don’t need tape seams on either of those materials.

Some people prefer using Taper Lock Tape because it can be easier to work with, but some installers swear by Vinyl Backer Rod, a cheaper alternative with its pros and cons.

You may have heard that you should “double-tape” your seams if they’re going to be moisture-exposed; this isn’t strictly necessary.

But I highly recommend doing it anyway – not only does it help seal out water more effectively.

But Double-T joints also lay flatter for cleaner, more professional-looking seams.

Can I Use Hardibacker In A Shower?

Yes, you can, since it’s waterproof. However, keep in mind that the seams will require sealing with Weld Bond if you lay backer over drywall.

I would also suggest using screws instead of nails when applying Hardibacker to walls.

Necessary tools:

  • Wood Saw (to cut Hardibacker board to fit)
  • Small Bucket or container (for mixing thin-set mortar)
  • Silicone Caulking Gun (for applying caulk along the bottom edge of a backer board)
  • Grout Sponge (optional – for cleaning up excess grout on finished shower floor surface)
  • Chalk Line (optional – for perfectly straight lines between tiles later on)
  • Tile Cutter (if cutting tiles yourself instead of buying pre-cut from a store)
  • Shovel (for mixing mortar in the wheelbarrow)
  • Wheelbarrow (to mix and transport mortar in – this will be messy)

While Hardibacker is waterproof, it’s advisable to use grout of at least water-resistant quality between your tiles.

All good tile stores should sell suitable grouts for areas that get wet regularly. You can also buy one-part waterproof or two-part marine grade “wonder” grout.

Which is more expensive but worth it if you think you might get some moisture on your shower floor often.

If installing the backer board over drywall, you’ll need to apply a thin-set with a notched trowel, so the thin-set penetrates the paper on some of the drywall seams.

Use Redgard Over Hardibacker

This will help seal against moisture later on when you lay your tiles, and it will also reduce movement of the backer board, which can cause tiles to crack or break from stress.

What Side Of The Hardibacker Board Faces Out?

The rough side looks like regular drywall goes inside the shower for better support and protection against damage.

And don’t worry about it not being aesthetically pleasing; there’s plenty of tiles to cover up any seams left by Hardibacker boards on the outside.

Yes, it’s the rougher side that will face out and be clearly seen.

Hardibacker is a popular substrate for tiling showers because it does not rot or mold and is very strong and durable.

The drywall side of Hardibacker boards may look like regular drywall.

Still, they are cement and vermiculite made, making them lighter than true drywall, waterproof, and rot-resistant.

The board has no actual use other than providing a surface for tile installation, so who cares what side faces out if the job gets done right. 

When working with Hardibacker in your shower, don’t worry about water damaging an unfinished (and porous) backside. Water cannot pass through the cement front.

You only have to worry about water damage if there are gaps between boards with neither tape nor thin-set utilization.

In these cases, water can wick from one board to another and force its way into the wall cavity.

Ensure that all seams are well taped and sealed before tiling or caulk any gaps after installation with compatible silicone caulk.

Can You Cut Hardibacker With A Jigsaw?

Yes, you can cut Hardibacker with a jigsaw. If the piece is small enough and on straight, it’s effortless to use a standard blade and clamp down hard during the entire cut.

If it’s larger than probably 12″ x 12″ or so.

I would suggest scoring as deep as you can get on both sides of your line before making your first actual cut to prevent chipping at all costs.

Another way to go about this is if you’ve got some feathers sticking out of either side of what you’re cutting (be careful not to lose track of which side belongs where).

Then rout right through them with a fair bit that will leave everything nice and flush, no problem.


It’s essential to know the differences between Hardibacker and Redgard if you are looking for a waterproofing solution.

The most often question I get asked about these two products is whether one needs to use them together, but the answer is No.

Both products can stand on their own for moisture protection;

However, there are some instances where one might work better than the other, depending on your specific situation.


Hi! I I faced many questions from customers about different products, and there was hardly any help on the internet. After learning all the things about these products as a manager the hard way, I decided to start a blog and help other people.

Recent Posts