How to Treat Joints in Magnesium Wall Board for a Smooth Finish

01 Sep How to Treat Joints in Magnesium Wall Board for a Smooth Finish

You need to treat joints in magnesium wall board with care to get a smooth finish. Start by acclimating the boards for several days so they adjust to the room’s temperature and humidity. Leave small gaps between sheets to allow for expansion and contraction. Use flexible fillers and reinforce joints with fiberglass tape to prevent micro-cracking. Sand and apply durable compounds for a seamless look. These steps help you avoid cracks and keep your walls looking clean and strong.

Key Takeaways

• Keep magnesium wall boards inside for a few days before you use them. This helps them get used to the room’s temperature and humidity.

• Put fiberglass mesh tape and flexible joint compound on the seams. This stops cracks and makes the joints strong.

• Spread joint compound in thin, even coats. Let each coat dry all the way before you sand and add another layer.

• Fill screw holes and be careful with corners. Use the right adhesives and caulks to make the walls smooth and strong.

• Put a concrete or masonry primer on the wall before you paint. This helps the paint stick better and stops it from peeling.

Magnesium Wall Board Prep

Clean and Dry

You need to start with a clean and dry surface before you treat any joints. Dust, dirt, or moisture can weaken the bond between the joint compound and the magnesium wall board. Always store your boards indoors in a cool, dry place. Make sure the boards stay away from water and direct sunlight.

Tip: Let the boards sit in the room where you plan to install them for at least 48 hours. For best results, keep them there for 3 to 5 days. This step helps the boards adjust to the room’s temperature and humidity. If you have an HVAC system, turn it on at least 72 hours before you bring the boards in. Stable temperature and humidity help prevent micro-cracking and make sure the joint compound dries evenly.

Check that the boards feel dry to the touch. If you notice any damp spots, wait until they dry completely. This step helps you avoid problems later.

Align and Smooth Edges

Proper alignment and smooth edges make a big difference in the final look of your wall. Place each magnesium wall board so the edges line up straight. Gaps or uneven edges can cause cracks or bumps after you finish the joints.

Follow these steps to prepare the edges:

1. Use a grinding tool to smooth out any rough or uneven cuts on the edges of the boards.

2. After you apply the joint compound and it dries, sand the surface lightly with sandpaper. This makes the surface even with the rest of the board.

3. Use putty knives or trowels to apply and smooth the joint compound and tape. These tools help you keep the edges aligned and ready for finishing.

Taking time to align and smooth the edges now will help you get a seamless finish later. You will also make the joint treatment process much easier.

Joint Treatment

Apply Mesh Tape

You need to reinforce every seam before you apply any compound. Fiberglass mesh tape works best for magnesium wall board. This tape is strong, flexible, and resists damage from moisture and chemicals. It helps prevent cracks and keeps your wall smooth for years.

Follow these steps to apply mesh tape:

1. Make sure the seams are clean and dry.

2. Cut the fiberglass mesh tape to fit each seam. Use 2-inch wide tape for flat seams. For corners, use 4-inch tape or overlap two strips of 2-inch tape by three-quarters of an inch.

3. Place the tape directly over the seams. Press it down so it sticks well and has no air bubbles or wrinkles.

4. Overlap the tape at least one inch where two pieces meet. This overlap adds strength and helps prevent cracks.

Tip: Use alkali-resistant mesh tape. It lasts longer and stands up to the cement in magnesium wall board.

Use Joint Compound

After you tape the seams, you need to cover them with joint compound. This step fills gaps and creates a smooth surface.

Here is how you do it:

1. Mix the joint compound and let it sit for about 15 minutes. This helps it cure better.

2. Use a putty knife or trowel to spread a thin, even layer of compound over the tape. Feather the edges so the compound blends into the wall.

3. Let the first layer dry completely. Drying time depends on the product and room conditions, but it usually takes several hours.

4. Apply a second layer, making it a little wider than the first. Let it dry again.

5. If needed, add a third layer for a perfectly smooth finish.

You can use a sandable elastomeric compound or a standard joint compound. Both work well for magnesium wall board. Make sure you follow the manufacturer’s instructions for the best results.

Note: Keep the room at a steady temperature and humidity while the compound dries. This helps prevent cracks and ensures a strong bond.

Sand Smooth

Once the joint compound dries, you need to sand the surface. Sanding removes bumps and blends the seams with the rest of the wall.

• Start with 80 grit sandpaper. This grit smooths out rough spots and levels the surface.

• After the first sanding, check for low spots or rough areas. If you find any, add more compound and sand again.

• For a super smooth finish, use 240 to 300 grit sandpaper for the final sanding.

• Always wipe away dust after sanding. A clean surface helps paint or primer stick better.

Safety Reminder: Wear a dust mask and goggles when sanding. Joint compound dust can irritate your eyes and lungs.

Taking your time with these steps gives you a seamless, professional look. Proper joint treatment keeps your magnesium wall board strong and looking great for years.

Corners & Fasteners

Fill Screw Holes

You need to fill every screw hole and fastener indent to create a smooth, even wall. Start by checking each board for visible screw heads or small dips where fasteners sit. Use a putty knife to press joint compound or spackle into each hole. Make sure you fill the indent completely. Wipe away extra compound so the area stays flush with the board.

Let the compound dry fully. After drying, sand the area lightly with fine-grit sandpaper. This step removes bumps and helps the patch blend with the rest of the wall. If you see any low spots, add another thin layer of compound and sand again. Repeat until the surface feels smooth to the touch.

Tip: Always use a sandable, paintable compound for screw holes. This choice makes finishing easier and gives you a better result.

Treat Corners

Corners need special care to stay strong and crack-free. You can use adhesives and caulks designed for magnesium wall board to bond corners and seal joints. Here are some recommended products and steps:

• Chemcraft M1 or moisture cure urethane adhesives work well for bonding magnesium wall board to itself, metal, wood, or EPS foam.

• For outside corners, glue the boards together. After the adhesive sets, sand or route the corner smooth. Fill any gaps with caulk, plaster, or grout.

• Inside corners can be glued or joined with a bead of painter’s caulk. Use non-shrinking, paintable caulk for best results.

• Polyethylene backer rods help control the depth of the joint. Place them in larger gaps before applying caulk.

• After caulk cures, apply primer and a thin coat of spackle or gypsum mud to hide imperfections.

You may use self-adhesive fiberglass tape for extra reinforcement at corners. This tape, combined with joint compound, helps prevent cracks in moist environments.

Note: Remove any extra adhesive or caulk with a putty knife before it dries. Clean joints look better and last longer.

Taking time to fill screw holes and treat corners gives your wall a professional, durable finish. Proper bonding and sealing keep your magnesium wall board strong for years.

Finish Surface

Prime

You must prime magnesium wall board before painting or adding texture. Priming helps the paint stick better and keeps the finish smooth. Magnesium wall boards have an alkaline surface, so you need a primer made for concrete or masonry. This kind of primer makes the surface neutral and stops peeling or flaking.

• Clean the wall and make it smooth before priming. Remove all dust and check that the wall feels dry.

• Pick a primer that works with magnesium wall board and joint compound. Some good choices are:

  • Concrete or masonry primers

  • UMA Acrylic Bonder and Primer/Sealer, which sticks to hard-to-paint surfaces and works with many paints

• Spread the primer evenly over the whole wall. Use a roller or brush for the best results.

• Let each coat dry all the way before adding another. This step gives you a strong, even base for paint or texture.

Tip: Keep the room at the same temperature and humidity while priming. This helps the primer dry right and stops cracks.

Paint or Texture

After priming, you can paint or add texture to your wall. Magnesium wall boards give you a smooth surface, so painting is easy. You can pick from many finishes to fit your style and needs.

You can use latex, oil-based, or special paints if you use the right primer. For more protection, seal the wall with a clear coat. This helps stop moisture and stains.

• Sand the wall after priming if you want it super smooth.

• Put on paint or texture in thin, even coats. Let each coat dry before adding the next.

• For textured finishes, use special rollers or trowels to make patterns.

Note: Magnesium wall boards resist fire and moisture, so your finish will last longer and look better if you follow these steps.

If you do these steps, you will have a strong, nice-looking wall that lasts and matches your style.

Best Practices

Quality Materials

You should always choose high-quality materials for your project. Good mesh tape, joint compound, and primer make a big difference in the final result. Cheap products can crack, peel, or fail to bond with the magnesium wall board. When you pick trusted brands, you get better strength and a smoother finish. Look for products that work well with cement-based boards. Read the labels and check for compatibility. If you use the right materials, your wall will last longer and look better.

Tip: Ask your supplier for recommendations if you are not sure which products to use. Many stores have experts who can help you choose the best options for your needs.

Drying Time

You need to let each layer dry fully before moving to the next step. Rushing the process can cause cracks or uneven surfaces. Most joint compounds need several hours to dry, but some may take longer if the room is cold or damp. Always check the product instructions for exact drying times. Use a fan or open windows to help air flow, but avoid direct heat. Patience gives you a stronger, smoother wall.

Avoid Mistakes

You can avoid common mistakes by following a few simple rules:

• Do not skip cleaning the surface before you start.

• Never use regular drywall tape on magnesium wall board. Always use fiberglass mesh tape.

• Do not apply thick layers of compound. Thin, even coats work best.

• Sand gently to avoid damaging the board.

• Always read and follow the manufacturer’s instructions.

Note: Careful work at each step helps you get a smooth, professional finish. Small mistakes can lead to big problems later.

You can get a smooth and strong finish on magnesium wall board if you follow each step. Use good materials and always look at the manufacturer’s rules for joint treatment. If you use best practices, you get many long-lasting benefits:

• Your walls will not crack easily and will resist water and mold.

• You will spend less money fixing your walls later.

• The boards will last longer and help keep the air inside clean.

Manufacturers usually suggest these steps:

1. Use wide fiberglass tape and joint compounds that work with magnesium wall board.

2. Put on non-shrinking caulk and primer.

3. Let the boards get used to the room before you install them.

4. Leave small spaces between boards so they can move.

For the best results, always read the product instructions and check the guidelines before you start your project.

FAQ

How do you prevent cracks in magnesium wall board joints?

You should use fiberglass mesh tape and flexible joint compound. Always let each layer dry before adding the next. Keep the room at a steady temperature and humidity. These steps help stop cracks from forming.

Can you use regular drywall tape on magnesium wall board?

No, you should not use regular drywall tape. Always use fiberglass mesh tape. It sticks better and resists moisture. This tape gives you a stronger, longer-lasting joint.

What primer works best for magnesium wall board?

You need a primer made for concrete or masonry. UMA Acrylic Bonder and Primer/Sealer also works well. These primers help paint stick and stop peeling.

How long should you let joint compound dry before sanding?

Let each layer of joint compound dry for at least 4 to 24 hours. Drying time depends on the product and room conditions. Always check the label for exact times.

Do you need to leave gaps between magnesium wall boards?

Yes, you should leave small gaps between boards. These gaps let the boards expand and contract. This step helps prevent cracks and keeps your wall smooth.