Whether you’re finishing a new installation or repairing old walls, unsightly gaps between drywall sheets can ruin the look of a room. These gaps, if not handled correctly, can lead to cracks and an uneven finish after painting. Many DIYers feel intimidated by drywall work, thinking it requires a professional touch to get that perfectly smooth, seamless wall. However, with the right materials and a bit of patience, anyone can achieve a flawless result.
Learning how to fill gaps in drywall is a fundamental home repair skill that ensures a professional-looking paint job. It’s a process of taping and applying joint compound, often called “mud,” to create a strong, durable, and invisible patch. This guide will provide clear, beginner-friendly instructions to help you tackle this essential task and prepare your walls for a beautiful finish.
Why Properly Filling Drywall Gaps Is Essential
Properly filling gaps in drywall is crucial for both the structural integrity and the final appearance of your walls. These gaps are weak points, and if they aren’t bridged correctly with tape and compound, they will almost certainly develop cracks over time as the house settles.
A well-executed wall repair creates a continuous, strong surface that is ready for primer and paint. Taking the time to do this step correctly ensures a smooth, seamless finish that makes the joints disappear completely, giving your room a professional and polished look that will last for years.
7 Step-by-Step Guide: How to Fill Gaps in Drywall
Step 1: Assess the Gap and Prepare the Area
Before you begin, it is important to assess the size of the gaps you need to fill. Gaps smaller than 1/8 of an inch can typically be filled with just joint compound and tape. For larger gaps, up to 1/2 an inch, you should pre-fill them before taping.
Prepare your work area by laying down drop cloths to protect the floor from dust and compound. Ensure the drywall surface is clean, dry, and free from any dust or debris. Also, check for any protruding screw or nail heads and drive them slightly below the drywall surface.
Step 2: Pre-Fill Any Large Gaps
If you have gaps wider than 1/8 of an inch, pre-filling them is a critical first step. Use a setting-type joint compound, also known as hot mud, for this purpose as it is stronger and more resistant to shrinking and cracking than all-purpose compound. Mix the hot mud according to the manufacturer’s directions to a thick, peanut-butter-like consistency. Using a 4- or 6-inch putty knife, press the compound firmly into the gap. Scrape off any excess so the fill is flush with the drywall surface. Allow this pre-fill to set completely before moving on.
Step 3: Apply the First Coat of Compound and Tape
Once any pre-filling is dry, you can apply the first layer of compound and tape. Using a 6-inch drywall knife, apply a thin, even layer of all-purpose joint compound over the seam, extending about 2 inches on either side of the gap. While the compound is still wet, cut a piece of drywall tape to the length of the seam. Press the tape firmly into the wet compound, centering it over the joint. This embedding process is a crucial technique for anyone learning how to fill gaps in drywall.
Step 4: Smooth the Tape and Remove Excess Compound
With the tape embedded in the wet compound, you now need to smooth it out and remove the excess material from underneath. Hold your 6-inch drywall knife at a 45-degree angle and press down firmly, drawing the knife along the entire length of the tape. This action forces a thin layer of compound through the tape’s pores and removes all the excess from underneath, ensuring there are no air bubbles. You should be left with a very thin layer of compound over the tape. Let this first coat dry completely, which typically takes 24 hours.
Step 5: Apply the Second Coat of Compound
After the first coat is completely dry, you will apply a second, wider coat of joint compound. This is known as the fill coat. Using a wider, 10-inch drywall knife, apply a fresh layer of compound over the taped seam. This time, extend the compound a few inches beyond the edges of the first coat. The goal is to feather the edges of the compound smoothly into the wall. Apply pressure to the outer edges of your knife to create a tapered effect, leaving a slightly thicker layer in the center over the tape.
Step 6: Apply the Final Skim Coat
Once the second coat is fully dry, it’s time for the final skim coat. This last layer is very thin and is meant to smooth over any remaining imperfections, creating a seamless finish. Use your 10-inch or an even wider 12-inch drywall knife for this step. Apply a very thin coat of joint compound over the entire patched area, extending the feathered edges even further. At this stage, you are aiming for the smoothest possible surface. Don’t worry about getting it absolutely perfect, as the final sanding will take care of minor ridges.
Step 7: Sand the Area for a Seamless Finish
Sanding is the final step in the process of how to fill gaps in drywall, and it’s what creates the perfectly smooth surface ready for priming. After the final skim coat is completely dry, lightly sand the entire area. Use a fine-grit sandpaper (120- or 150-grit) on a sanding block or a pole sander.
Use gentle pressure and a circular motion to smooth out any ridges or tool marks. Your goal is to blend the patched area seamlessly with the surrounding wall. Be careful not to oversand and expose the drywall tape underneath.
Common Drywall Mistakes
When working with drywall, there are several common mistakes to watch out for. One frequent error is applying too much joint compound at once. This can result in uneven drying, cracks, or excessive sanding later. Another common mistake is improper taping, such as failing to press the tape firmly into the joint compound, which can cause bubbles or peeling.
Skipping sufficient sanding between coats is another issue, leading to an uneven surface that becomes more noticeable after painting. Additionally, some people fail to ensure the screws or nails are driven slightly below the drywall surface, which can leave bumps that disrupt the finished look. Understanding and avoiding these errors will help achieve a professional and polished drywall finish.
Frequently Asked Questions
What Is the Best Compound for Filling Drywall Gaps?
For pre-filling large gaps (wider than 1/8 inch), a setting-type compound (“hot mud”) is best because it’s strong and resists shrinking. For the taping and finishing coats, a standard all-purpose or topping joint compound is ideal. All-purpose compound works well for all steps, while topping compound is slightly easier to sand for the final coat, providing a smoother finish.
Should I Use Paper Tape or Fiberglass Mesh Tape?
Paper tape is generally recommended by professionals for filling flat seams on drywall. When properly embedded in joint compound, it creates a stronger, more crack-resistant joint than mesh tape. Fiberglass mesh tape is self-adhesive and easier for beginners to apply, but it is more prone to cracking over time if not used with a setting-type compound. For maximum durability, paper tape is the superior choice.
What Is the Biggest Gap You Can Fill in Drywall?
You can fill gaps up to about 1/2 inch wide using a pre-filling technique with a setting-type joint compound before taping. For gaps larger than 1/2 inch, you should not just fill them with compound. Instead, it’s better to cut a new piece of drywall to fit the gap, creating a patch. This ensures a more stable and durable wall repair that won’t crack.
How Do I Avoid Bubbles Under My Drywall Tape?
Air bubbles under paper tape occur when the tape is not properly embedded in the joint compound. To avoid this, make sure you apply a sufficient and consistent bed of compound before laying the tape. When you press the tape into the mud, use a firm, even pressure with your drywall knife to squeeze out all the excess compound and any trapped air from underneath.
How Long Should I Wait for Joint Compound to Dry?
Drying time depends on the type of compound, the thickness of the application, and the humidity in the room.
- Setting-type compound (hot mud): Dries via a chemical reaction and is usually hard in 20 to 90 minutes, depending on the type.
- All-purpose compound: Dries via evaporation and typically needs 24 hours to dry completely between coats. In humid conditions, it may take longer.
Conclusion
Mastering how to fill gaps in drywall is a fundamental skill that elevates the quality of any room renovation or repair, ensuring a truly professional and long-lasting result. While the process requires patience, it is straightforward when broken down into manageable steps. By properly preparing the surface, using the right materials, and applying thin, successive coats, you can create a perfectly smooth and invisible transition between drywall panels.
Don’t let imperfect drywall seams undermine your hard work. By following this guide, you have the knowledge to tackle this task with confidence. Embrace the process, and take pride in creating walls that are as durable as they are beautiful.