A large gap between sink and wall: how to Fill, close or seal it

You might notice a big gap between your sink and the wall. This can be annoying as water and dust can fall behind the sink. It can be hard to clean in this area.

Furthermore, it doesn’t look very nice. Let’s take a look at how we can fill this gap between the sink and wall.

How to seal a large gap between the sink and the wall?

Depending on the size of the gap between the sink and the wall, you need to use various techniques to fill it up. Here are some of the common techniques-

Breaks up to one-fourth inch

Caulk is the best material to fill in gaps of up to one-fourth of inches. It is a flexible material that gets pushed inside the hole and fills it. After a while, the chalk dries up and creates a waterproof barrier.

If you have installed tiles on the wall next to the sink, you will need to select a caulk that is close to the color of the grout. Use sanded caulk to fill gaps larger than one-eighth of an inch. Use normal caulk for gaps smaller than one-eighth of an inch.

First, ensure that the gap between the bathtub and the wall is dry, and clean and there are no other items lying there. Cut the upper part of the caulk tube and squeeze out a thin bead of caulk into the gap.

Using your wet fingers, spread out the caulk smoothly and you should be done. Let it dry for a while before you take a bath. It will be necessary to redo this every few years. It is important to inspect the chalk from time to time to see if it is still properly sealing the hole.

Check out this video to get a better idea-

There are different types of chalk. Make sure that you get a big brand such as Loctide as they use qualitative materials. Cheaper chalks might not last that long. This is not something that you want to save money on as bad materials can lead to a lot of problems.

Gaps of up to half-inch

If you have a gap between your sink and the wall that is between one-fourth of an inch to half an inch, here is what you do. You will have to use two streaks of caulk in the gap. First, you will need to apply one streak of caulk along the side of the bathtub, and then the second layer will be touching the wall. Immerse your finger in water and join both beads properly so that it appears like one thick line.

This can be more challenging to do and you might have to ask your plumber to do this for you. Water can get in small holes so it is important that you get it done properly. Water can create damage as it builds up over time so you have to be careful when you clean the caulk so that it doesn’t get dented.

If you install the backer board properly, you can also avoid a lot of gaps around the bathtub. By moving it around slightly, you can already close some holes.

Very large gaps

If the gap is up to six inches, you will need some backer rods. Since backer rods are stretchy foam tubes, they will perfectly fit into the gap. While buying the backer rod, just check with the hardware store if it is meant for areas that get humid and moist. These rods tend to absorb water, and that is not what we are looking for.

Then insert the backer rod inside the gap and allow it to fill in the gap. Now use a streak of caulk to seal the backer rod to the bathtub from one end and the adjoining wall from the other end. There are tools that make it easier to install the backer rods but a screwdriver often works.

You can add some silicone to finish things off. This is done as we discussed before and ensures a tight seal. Check your local code to make sure that this is allowed.

You can also use a plastic water strip dam to close the gap. This can be a more durable solution. You can use a saw to cut it to size. Once again, you can use some silicone to properly seal the hole.

Most often it is better to expand the drywall or tiles so that you have a smaller gap. Backer rods can work but they are more fragile and can lead to problems over time. They are often used as a temporary solution. Backer rods also don’t look that nice and can break down after a few years. This is why most plumbers will advise that you close down the gap by adding some waterproof material. It is a common problem and plumbers want durable solutions.

To conclude, we can state that it is annoying if there is a gap between the sink and the wall. Luckily this is often quite easy to fix. With some cheap materials, it is possible to fill this gap. This gives your sink and vanity a nicer look. If the gap is really big, it might be better to extend the drywall.

It might be necessary to update the chalk often. You can use a caulking gun to do this. This is something that almost every DIY’er can do. It can take some practice to use this but after a while, you will get the hang of it.

The gap between the sink and the wall should be waterproof. Mold can grow in this area if water drips behind the sink. This can lead to bad mold smells and other problems. In this post we have outlined how you can avoid this problem.