How to Fill a Large Gap Between a Baseboard and Floor

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how to fill large gap between baseboard and floor

Living in an old house can be an exciting adventure. However, with old houses come new problems and some are easier to fix than others. 

A common issue with old homes, and even new homes, is a large gap between the flooring and the baseboard on the walls. 

This gap can be a source of drafts and prevent your home’s HVAC system from being as efficient as possible. Because of this, you will want to close that gap and make sure it stays sealed year-round. 

In this article, we have compiled some methods for filling a large gap between a baseboard and floor. Any of these approaches will do the job and keep your home air tight when the weather gets cold. 

Key Takeaways

Here’s the general idea:

  • Fill your gaps if they’re larger than a quarter’s width.
  • Add a floorboard trimmed to your ideal width to snap it into place.
  • Carefully size, cut, and apply shoe molding, and secure with nails.
  • Mask the surrounding floor and fill the gap with waterproof caulk (e.g., latex). Use sparingly and smooth over with a putty knife.
  • Cut and apply silicone trim strips that self-adhere.

Filling a Gap Between a Baseboard and Floor: Basic Idea

The right method for filling a gap between the baseboard and floor depends on the size and location of the gap. 

Some of the ways to get this space sealed include:

  • Adding a floorboard
  • Installing shoe moulding
  • Filling the gap with caulk
  • Using flexible trim strips

How Much of a Gap is Acceptable?

how much gap is acceptable

When homes are built, there will always be some variation in how things are done. This is one of the things that makes home ownership unique and interesting. 

Advice from the Expert: From my own experience, I’ve found that when dealing with larger gaps, using a combination of methods can often provide the best result. For example, I usually start by installing a trim strip to reduce the size of the gap, then follow up with a bit of caulk to ensure a tight seal. It’s a bit more work, but the result is worth it.

However, gaps between the flooring and baseboards could be the result of poor craftsmanship. If the gaps are large, you will want to fill them in to get a cleaner, more modern look. 

If a gap is more than the width of a quarter, you should fill it in. Gaps that are smaller than this, however, will probably not be noticeable once there is furniture in the room. 

Whether or not you fill these gaps is up to you. If they are large enough to let in cold air or are especially noticeable, it might be a good idea. 

Add a Floorboard

If the gap is due to the floor not reaching the baseboard, this can be remedied by adding another floorboard. 

Trim a floorboard to a desired width that will tuck underneath the baseboard. If the baseboard is low enough, you should be able to completely seal the gap. 

You may not have access to the original flooring materials that your home was built with. Since this is a trim piece that will not be load bearing, you can use thinner flooring pieces if you must. 

If your flooring is tongue and groove, you should be able to snap the new floorboard into place. If it is not, you will have to secure it to the flooring joists themselves. 

Once the new floorboards are in place, the gap should be sealed or small enough to keep cold air out. 

Add Shoe Moulding

add shoe moulding

If the gap between your flooring and baseboards is due to the baseboard being too high, there is another solution. Shoe moulding is an L-shaped trim piece that is meant to cover gaps just like this one. 

When installing the shoe moulding, you will have to ensure that it is the correct size. Buying moulding strips that are too short may not cover the gap completely. 

If the room you are working in already has trim moulding, you should be able to find a style that matches. 

Cut and measure the shoe moulding, and secure it in place with finishing nails. Then, you can paint it to match the walls for a seamless fit. 

Fill in the Gap With Caulk

Advice from the Expert: Remember, if you’re using caulk to fill the gap, make sure to let it dry for 24 hours before you do anything else. In my haste once, I didn’t allow the caulk to properly dry and I ended up having to redo the whole process. You can avoid that mistake by just giving it the time it needs to set.

Shoe moulding may not fit in with your home’s particular style. If you want to maintain a modern, contemporary look, filling in the gap with caulk is a good option. 

Choose a waterproof, latex caulk that is paintable for this job. This will ensure that it seals off the gap and makes it airtight to keep heat in. 

Apply the caulk sparingly with just enough to cover the space. Then, use a putty knife to smooth it out and make a flush joint that lines up with the wall. 

Be sure to mask the floor when applying the caulk to keep it from staining the floorboards.

Use Trim Strips

Trim strips are self-adhesive, silicone-based strips that are designed to fit perfectly in trim gaps. 

They are a perfect solution if you don’t want to risk marring your baseboards or floors with paint or caulk. They fit in the gaps and seal themselves with their adhesive backing. 

Simply cut the trim strips to the right length and apply them to the gap. They will fold between the flooring and baseboards and form a tight seal that is just as effective as caulk. 

Trim strips come in many colors, so you are sure to find some that match the paint on your wall. 

Advice from the Expert: This is something folks tend to overlook – the color of the caulk, trim strip, or molding should closely match your baseboard and floor. It may seem like a minor detail, but trust me, mismatched colors can make the job look unfinished, or worse, amateurish. Taking the extra step to color match can make a big difference in the end aesthetic.


faq how to fill gap between baseboard and floor
  • How high should baseboards be off the floor?

If you plan on installing carpet, your baseboards should be about 1 inch off the floor. This will give you enough room for the padding and the carpeting. 

If you are leaving the floors uncarpeted, you should not have any gaps. At most, the gap should be around the width of a quarter to prevent heavy drafts. 

  • Is it okay to caulk over old caulk?

For the most part, it is okay to put new caulk over old caulk. However, you should remove it if there is not enough room for the new caulk to be flush. 

Remove old caulk if it is rotting away or water damaged, as well. This will ensure that you will have a tight seal with the new caulking. 

  • What is the best paint for baseboards? 

Semi-gloss paint is ideal for baseboard trim pieces. It is durable and will help protect the baseboards from damage. 

The baseboards are a high-touch area that see a lot of bangs and bumps. Using a high-quality semi-gloss paint will provide a longer-lasting finish. 


Efficiency and style are incredibly important considerations for homeowners. By sealing off any gaps or openings, you can keep your home eco-friendly and warm in the winter. 

Sealing the gaps in your floorboards will also give your home a finished, polished look. Small details count in interior design and this is an easy issue to remedy. 

Photo of author


Michael J. O’Connor is a writer and marketing specialist from the Bay Area of California. A graduate of Sonoma State’s Creative Writing program, he spent many years as a contractor and carpet layer, learning the ins and outs of flooring and general contracting. When he’s not typing away at his desk, he enjoys hiking with his dogs, woodworking and collecting rare books. See full biography here.

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