Should you use green board or cement board in a shower? The Ultimate Guide

If you‘re renovating or building a shower, choosing the right backer board is one of the most critical decisions you‘ll make. Getting it wrong can lead to mold, damage, and expensive repairs down the road. The two most common options for shower boards are green board and cement board. But how do you decide between them?

In this comprehensive guide, I‘ll walk you through everything you need to know to choose the best shower backer board for YOUR specific project. After installing countless showers over my 10 years as a contractor, I‘ve seen firsthand how green board and cement board perform over time. I‘ll share my real-world expertise so you can avoid mistakes and end up with a gorgeous, waterproof shower that will last for decades.

Grab a beverage, get comfortable, and let‘s dive in!

Green Board 101

Before we get into shower applications, let‘s start with a quick green board primer so you understand what it is…and what it isn‘t.

Green board is a moisture-resistant drywall that contains additives mixed into the gypsum core to repel some water. This treatment gives it the signature green color. It‘s also coated with fiberglass mats for added moisture protection.

Don‘t let the color fool you though – green board is NOT waterproof. It‘s designed to withstand high humidity and occasional water exposure. But it will absorb liquid water over time and degrade.

Now for some science! Green board achieves its moisture resistance from special acrylics or other chemicals added to the gypsum, like wax or silicon. These repel small amounts of moisture. Meanwhile, the outer fiberglass facers provide a water-tight barrier on the surface.

But with enough water exposure, liquid can still penetrate those outer layers and saturate the gypsum core. When that core gets wet, it loses structural integrity and strength.

In summary:

• Made from gypsum with moisture-resistant additives
• Provides some water repelling ability
• Outer fiberglass layers assist with moisture barriers
• Can tolerate humidity and occasional splashing
• NOT equivalent to waterproof cement board

With that green board background, let‘s see how it stacks up against cement board.

Cement Board vs. Green Board for Showers

Cement board, also called tile backer board or WonderBoard, contains no paper or gypsum. It‘s constructed from cement and other minerals formed into a solid concrete slab.

The cement makes it inherently waterproof and unable to be penetrated by water the way green board can. It‘s also reinforced with embedded glass mesh for phenomenal strength and stability.

Cement board never loses integrity or structural soundness, even when constantly soaked. That‘s why professionals strongly recommend it for showers and wet rooms over moisture-resistant drywall alternatives.

Let‘s compare the key factors:

Property	Green Board	Cement Board
Material	Gypsum + additives	Cement + minerals
Water resistance	Moisture-resistant only	Fully waterproof
Strength	Prone to sagging when wet	Extremely durable
Mold potential	High if moisture present	Very low
Cost	$$	$$$

As you can see, cement board beats green board in every area except upfront cost. I always remind clients that "good, fast, or cheap – pick two."

Yes, green board is cheaper initially. But cement board will save you money and headaches for decades down the road due to its longevity and waterproofing.

Now let‘s walk through exactly how to install both types of boards so you know what‘s involved.

Installing Green Board in Showers

Green board can be an appropriate choice for some showers IF installed properly. Here are step-by-step instructions:

Pick the Area Wisely

Avoid direct water contact on green board. It should only be used on walls or ceilings that receive occasional splashing or condensation, not direct spray. Opt for cement board on shower floors/pans.

Prepare the Wall

Remove existing finishes down to studs. Inspect for plumb, level, and any damage – address underlying issues before installing green board.

Add a Barrier

Cover studs with 6mil plastic sheeting or a roll-on water barrier. This provides emergency water protection if moisture penetrates the green board.

Cut and Attach the Boards

Use a utility knife to score and snap boards to size. Attach vertically to studs with 1 1/4” drywall screws every 8” along studs. Offset seams between rows.

Fill Seams

Fill all seams and screw holes with lightweight joint compound. Use fiberglass mesh tape at seams for strength. Feather out compound to create a smooth finish.

Seal Everything

Caulk and seal all seams, corners, edges, and joints with silicone. Careful waterproofing is crucial!

Finish and Maintain

Apply finishes like tile or paint designed for moisture-resistance. Re-caulk and seal yearly to maintain waterproofing abilities.

The keys with green board are managing moisture exposure and meticulous sealing. If you take those steps, it can perform well in some shower designs.

Next let‘s look at how to install the long-lasting cement board.

Installing Cement Board for Showers

Cement board installation takes more skill, but results in a bombproof shower substrate. Here‘s how it‘s done:

Fortify the Framing

Use 12 inch on-center studs. Double up studs at corners and niche openings. This prevents movement or cracks.

Hang the Board

Cut cement board to size with carbide-tipped cutters; scoring and snapping takes practice. Attach vertically with cement board screws every 8 inches.

Tape the Seams

Apply alkali-resistant fiberglass tape over all seams and corners. Set tape into a bed of thinset mortar for strength and sealing.

Prep Corners

Install corner beads with thinset at all inside and outside corners. Use polyethylene flashing beneath corners prior to taping.

Seal All Joints

Caulk every seam, change of plane, and transition with flexible silicone caulk. Tool the caulk with a putty knife for smooth finish.

Once your cement board substrate is installed, you can add any type of tile or waterproofing membrane you desire. It‘s also ready for curbless showers or other custom designs.

Next let‘s examine the all-important methods for waterproofing BOTH types of shower boards.

Waterproofing Green Board and Cement Board Showers

Waterproofing is mandatory for shower boards, but the methods differ by material:

Green Board Waterproofing

• Plastic membrane behind boards
• Epoxy grout for tile seams
• Liberal silicone caulk at seams/corners
• Seal board surface with waterproof paint

Cement Board Waterproofing

• Liquid membrane applied to surface
• Pre-membrane underlayment
• Fiberglass mesh tape with thinset
• Epoxy grout for tile
• Silicone caulk at changes of plane

As you can see, green board relies heavily on surface seals like caulk and paint to achieve "waterproofness." Cement board is inherently waterproof so your products simply enhance that existing protection.

I always tell homeowners to budget extra time and money for waterproofing steps with green board. It‘s easy to miss small gaps in caulk that can lead to moisture intrusion without the robust waterproof matrix you get from cement board installations.

Tiling and Finishing Shower Boards

The final layer in your shower is the aesthetic tile or other finishes. What you choose will depend on your underlying board:

Green Board Tile Tips

• Stick with smaller lightweight tiles to reduce sagging
• Allow tiles 1-2 days of cure time before grouting
• Use polymer-modified grout for flexibility and water resistance
• Seal tiles once fully cured

Cement Board Tile Tips

• Suitable for any tile type or size
• Follow manufacturer‘s directions for tile cure time before grouting
• Any grout type works but epoxy is best for waterproofing
• Sealing optional but provides extra water and stain protection

Other Finishes

• Use mold-resistant latex paint on boards
• Avoid vinyl or paper coverings
• Apply skim coats if using thick finishes to prevent unevenness
• Caulk edges and seams for both materials

And those are the key tips for finishing off your shower boards. Next let‘s examine an extremely important shower element – the curb.

Building Shower Curbs Right

The curb (also called a dam) is a raised barrier along the edge of a shower floor that prevents water from flooding out.

On shower curbs, cement board is always the best option. Its innate waterproofing and strength are ideal for containing water in the pan. The rigidity also enables pre-sloped curbs for accessibility.

With care, green board can also be used:

Green Board Shower Curbs

• Must be paired with membrane underlayment
• May require additional framing for support
• Use silicone sealant around all edges
• Cover with waterproof coating like RedGard
• Inspect seals regularly to ensure water containment

But honestly – don‘t bother trying to cut corners with green board curbs. Spend a few extra dollars and minutes for the cement board durability. Your future self will thank you!

Maintaining Your Shower Board Investment

Use these tips to keep your shower boards in tip-top shape:

Green Board Maintenance

• Inspect all caulk and grout twice yearly; re-seal gaps immediately
• Watch for soft spots that indicate moisture damage behind boards
• Address any cracks in grout lines right away to prevent water intrusion
• Re-paint walls with moisture-resistant paint periodically

Cement Board Maintenance

• Re-caulk corners and seams yearly or as needed
• Replace any cracked grout or thinset
• Inspect boards for cracks annually, repair with mesh tape and thinset
• Reapply waterproofing membrane every 3-5 years

Repairs

• Patch small green board holes with joint compound
• Replace saturated green board sections
• Cut out and patch small cement board areas
• Replace cement board in larger sections if extensively damaged

Routine maintenance preserves your shower substrate and prevents major damage or mold issues.

Cost Comparison: Green Board vs. Cement Board

Let‘s break down the typical material and installation costs:

Green Board Costs

• Materials only: $8-12 per 4×8 sheet
• Other supplies: $50-100 (tape, thinset, screws, caulk)
• Labor for DIY install: $3-5 per sq. ft.
• Pro installation labor: $6-10 per sq. ft.

Total for a basic 6×6 shower: $500-800

Cement Board Costs

• Materials only: $10-18 per 4×8 sheet
• Other supplies: $75-150 (screws, tape, blades, thinset, caulk)
• Labor for DIY install: $4-6 per sq. ft.
• Pro installation labor: $8-12 per sq. ft.

Total for a basic 6×6 shower: $700-1000

Yes, you‘ll spend more upfront on cement board. But remember – you‘ll likely spend that difference (and then some) down the road on green board repairs and replacements from moisture damage.

Green Board vs. Cement Board – The Final Verdict

While green board can be used in some shower applications, cement board is by far the superior choice for waterproofing, prevention of moisture damage, and long term durability.

Green board pros:

• Cheaper upfront cost
• Familiar to work with like drywall

Green board cons:

• Not waterproof
• Risk of deterioration and mold
• Requires intensive sealing and maintenance
• Shorter lifespan – higher cost long-term

Cement board pros:

• Totally waterproof and moisture-proof
• Extremely durable and rigid surface
• Resistant to mold growth
• No need for additional membranes
• Long lifespan – better value over time

Cement board cons:

• Higher upfront material cost
• More difficult to install
• Requires special tools to cut

If your budget allows, choose cement board for a worry-free shower substrate. For lower budget remodels with simple tile plans and limited water exposure, green board may suffice with proper installation and extensive sealing.

I hope this guide gives you confidence to tackle your shower project armed with the facts about green board vs. cement board! Don‘t hesitate to reach out if you need a hand getting your new waterproof shower installed. I‘m always happy to chat with fellow DIYers.

Happy building!

-Lillie