How to Float a Wall to Make It Plumb: The Ultimate Guide

Have you ever stared at a freshly hung sheet of drywall, only to realize it bows inward or leans slightly out of alignment? It is a frustrating moment for any DIYer or professional contractor. A wall that isn’t plumb doesn’t just look unprofessional; it causes issues with cabinetry, trim installation, and tile work later on.

The solution lies in a technique known as “floating” the wall. But how to float a wall to make it plumb correctly without causing cracks or structural issues? In this comprehensive guide, we will walk you through the exact steps, tools, and expert tips needed to straighten your walls effectively. Whether you are dealing with bowed studs or uneven existing drywall, this method will help you achieve that crisp, professional vertical line.

What Does It Mean to “Float” a Wall?

Before diving into the tools, it is crucial to understand the concept. In drywall terminology, “floating” a wall generally refers to attaching drywall sheets in a way that allows for minor adjustments or movement, often avoiding rigid attachment to certain framing members to prevent cracking. However, when we talk about floating a wall to make it plumb, we are referring to a corrective technique.

This process involves using shims, furring strips, or additional layers of drywall to build out specific areas of the wall frame. The goal is to create a new, perfectly vertical (plumb) surface over an imperfect frame. According to industry standards, a wall is considered “plumb” if it deviates no more than 1/4 inch in 10 feet vertically. If your walls exceed this tolerance, floating becomes necessary.

For a deeper understanding of construction tolerances and framing standards, you can refer to general construction principles outlined on Wikipedia’s page on Drywall.

Tools and Materials You Will Need

Success in this project relies heavily on having the right equipment. Trying to cut corners here will result in a wavy wall. Here is your checklist:

Essential Tools

• 4-foot and 6-foot Level: A high-quality spirit level is non-negotiable.
• Laser Level (Optional but Recommended): For long walls, a laser level provides a continuous reference line.
• Utility Knife: For scoring drywall and trimming shims.
• Drywall Screws (1-5/8 inch or 2-1/2 inch): Depending on whether you are adding a second layer.
• Drill/Impact Driver: With a dimpler bit to sink screws without breaking the paper face.
• Wood Shims or Composite Shims: Tapered wedges used to fill gaps.
• Furring Strips (1×3 or 1×4 lumber): Used if the deviation is significant (more than 1/2 inch).

Safety Gear

• Safety glasses
• Dust mask (N95 recommended)
• Work gloves

Step-by-Step: How To Float A Wall To Make It Plumb

Follow these precise steps to correct your wall alignment. This method assumes you are either correcting exposed studs before hanging drywall or adding a second layer of drywall over an existing imperfect wall.

Step 1: Identify the High and Low Spots

You cannot fix what you do not measure. Start by placing your 4-foot level vertically against the wall studs or existing drywall.

1. Hold the level firmly against the framing.
2. Look for gaps between the level and the wood/drywall.
3. Mark the high spots (where the stud bulges out) and the low spots (where the stud recedes).
4. Use a pencil to mark these areas clearly. If the bow is severe, use a chalk line to snap a vertical reference line from ceiling to floor at the deepest point of the bow.

Pro Tip: If you are working with an existing wall, remove any baseboards or trim that might interfere with your level’s placement.

Step 2: Determine the Correction Method

The severity of the bow dictates your approach.

For most residential issues, the shimming method is the most common application of learning how to float a wall to make it plumb.

Step 3: Apply Shims to the Studs

If you are hanging new drywall, this is the best time to act. If you are going over existing drywall, you may need to install furring strips first. Let’s focus on the standard stud-shimming technique:

1. Place the Shim: Insert a wood shim behind the stud at the location where the drywall will be screwed in. The thick end of the shim should face the direction needed to push the stud out (or fill the gap if the stud is recessed).
2. Check with Level: Place your level across the shim and the adjacent studs. Adjust the shim until the bubble is perfectly centered.
3. Secure the Shim: Once aligned, drive two drywall screws through the future drywall location into the stud and shim to hold it in place. Note: Some pros prefer to glue shims with construction adhesive to prevent squeaking.
4. Trim Excess: Use your utility knife to snap off the protruding ends of the shims so they are flush with the face of the stud.

Step 4: Hang the Drywall

Now that your framing is adjusted, hang the drywall as usual.

1. Lift the drywall sheet into place.
2. Ensure it aligns with your shimmed studs.
3. Drive screws every 12 inches on ceilings and every 16 inches on walls.
4. Crucial Step: When driving screws into shimmed areas, ensure you do not over-drive the screw. The goal is to pull the drywall tight against the shimmed stud without crushing the gypsum core.

Step 5: Verify Plumb Alignment

After the drywall is hung, perform a final check.

1. Place your 6-foot level vertically on the new drywall surface.
2. Check multiple locations along the wall.
3. If you see minor deviations (less than 1/16 inch), these can be corrected during the mudding and taping phase. If the deviation is larger, you may need to add a skim coat of joint compound to build up the low side.

Common Mistakes to Avoid

Even experienced DIYers make errors when attempting to plumb a wall. Here is what to watch out for:

• Over-Shimming: Using too many shims can create a “hard spot” that telegraphs through the joint compound. Always try to blend the correction over a wider area.
• Ignoring the Ceiling and Floor: Sometimes the wall is plumb, but the floor is sloped. Decide early whether you are plumbing to the true vertical (gravity) or parallel to a corner. True vertical is usually preferred for aesthetic reasons.
• Skipping the Adhesive: Shims can loosen over time due to house settling. Applying a dab of construction adhesive to the shim before screwing it in ensures a permanent, squeak-free fix.

FAQ: Frequently Asked Questions

1. Can I make a wall plumb after the drywall is already installed?

Yes, but it is more difficult. You can apply a “skim coat” of joint compound to build up low areas. For deviations greater than 1/4 inch, you may need to install furring strips over the existing drywall and hang a new layer of drywall. This is effectively how to float a wall to make it plumb in a renovation scenario.

2. What is the difference between “plumb” and “level”?

“Plumb” refers to vertical alignment (perfectly up and down), while “level” refers to horizontal alignment (perfectly side to side). Both are critical for professional-looking construction, but this guide focuses specifically on vertical plumbness.

3. Do I need a laser level to float a wall?

No, a high-quality spirit level (4-foot or 6-foot) is sufficient for most residential walls. However, a laser level speeds up the process significantly for long walls or commercial spaces by providing a continuous visual reference line.

4. How much does it cost to fix a bowed wall?

If you are doing it yourself, the cost is minimal—mostly the price of shims ($5–$10) and screws. If you hire a professional, expect to pay between $50 and $100 per hour, depending on the severity of the bow and local labor rates.

5. Will floating a wall reduce my room size?

If you use shims behind the drywall, the reduction is negligible (fractions of an inch). If you install furring strips and a second layer of drywall, you will lose approximately 1 to 1.5 inches of room depth.

6. Can I use cardboard as shims?

While cardboard is sometimes used in a pinch, it is not recommended for permanent solutions. Cardboard can compress over time or absorb moisture, leading to wall movement and cracked paint. Always use wood or composite plastic shims.

Conclusion

Learning how to float a wall to make it plumb is a valuable skill that separates amateur repairs from professional-grade finishes. By carefully identifying high and low spots, using the correct shimming techniques, and verifying your work with a reliable level, you can ensure your walls are perfectly vertical.

Remember, patience is key. Rushing the shimming process will only lead to more work during the taping and mudding stages. Take your time to get the frame right, and the rest of the finishing process will be smooth sailing.

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