How To Fill Gaps Between Your Pipes And Walls [Step By Step Guide]

Filling the gaps between the pipes and walls in your home is an important repair. However, covering some gaps can be challenging because they are in hidden or hard-to-reach locations. Based on our research, this post will provide an easy guide to help you fill those gaps. 

To fill the gaps between pipes and walls, follow the process below:

  1. Remove dirt and other debris around the pipes and the wall where they connect.  
  2. Fix the trailer skirting around the base of the pipe where it meets the wall.
  3. Use a suitable sealant around the opening of the pipes, on the top and bottom plates, and the subfloor.
  4. You can also add a lath or metal screening in the pipe ends to prevent rodents from entering.

You can successfully close the gaps when you follow the correct process and use suitable filling materials. When deciding what to use, you should consider the purpose and material of the pipes. Read on to learn more about how to fill gaps between pipes and walls and why it's important to do so.

copper and plastic pipes, fittings on concrete wall, How To Fill Gaps Between Your Pipes And Walls [Step By Step Guide]

Steps For Filling Gaps Between Pipes And Walls

Gaps between pipes and walls are susceptible to air pressure and foreign objects. It's important to fill in and seal the gaps to avoid any problems or malfunctions. 

Filling the gaps can be tricky, because many pipes are in hard-to-reach areas. It is best to fill gaps during new home construction, but it is also possible to retrofit existing homes. Just follow the procedure below. 

Horizontal snapshot of young plumber working with grey sewer pipes, fixing them to wall

Filling Small Gaps With Sealant Or Foam

Here is the process of how you can fill gaps between pipes and walls:

  1. Locate the pipe hole in the wall cavity.
  2. Remove dust and debris from the pipe hole. 
  3. Prepare the sealant material. If you use caulk, load it into the caulking gun. 
  4. Apply the sealant or foam to the pipe hole. Apply it via the top and bottom plates and the subfloor. Only apply a thin line and smooth it out. It should take about 24 hours for the caulk to seal.
  5. If you use foam, apply it to the pipe opening and smooth with a putty knife. Do not overfill because the foam expands. Wait 24 hours for the foam to dry.
  6. Seal the holes on the pipe rim joists.
  7. Use a damp rag to remove excess caulk or foam before it cures. You can remove cured sealant with a serrated blade or utility knife.

hand putting sealant on a hole in a wall for the pipe of ac be sealed

Filling Large Gaps

If the holes are large (more than 1/2 inch), follow these steps:

  1. Measure the diameter of the pipe hole to get the gasket width. Then cut accordingly.
  2. Apply the caulk to the top plate. 
  3. Place the gasket over the pipe. Firmly press it, so that it adheres well.
  4. Use the appropriate staple to put the gasket in place.
  5. Add more caulk around the pipe.
  6. Remove excess caulk.

When filling the gaps in heating pipes, you need to add insulation around the pipes if there is none installed. You should also ensure that the insulation has no gaps. Check if the pipes are next to the floor joists to prevent compressing the insulation.

Avoid filling the gaps of running water pipes along exterior walls. You only need to air seal the external wall framing and subfloor.  

Precautions When Filling Gaps

You should protect yourself from exhaling sealant fumes. The sealant is also difficult to remove, so you need some protective gear when working. Also, protect other objects surrounding the pipes to avoid splatters. 

When applying caulk or foam, always follow the product instructions before applying it to the surfaces. Keep the sealant materials away from open flames, because these are highly flammable.

What To Do After Filling The Gaps

After filling, you should conduct a visible check on the pipe gaps. For new constructions, ensure that you finish the filling process before drywall installation. You can do a blower door test to find out if you successfully filled the gaps.

What To Use To Fill Gaps In Pipes And Walls?

Plumber putting a paste sealant on the thread of a pipe

You have different options for pipe and wall gap fillers. The materials you use will depend on the size and type of the pipes and the wall surface. The fillers you select should be compatible with both pipes and walls.  

It is also important to use code-compliant sealing materials. Relevant codes have specific requirements, such as insulation or thermal envelope. Refer to this link to read the summaries of the various codes.

The common filling materials are caulk and canned spray foam. You should use a silicon-based caulk that is water-resistant.

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For gaps that are more than 1/2 inch, use an expanding foam sealant. The foam should withstand movement while keeping a tight seal.

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If the gaps are too large, you should use a blocking material like a pre-fabricated flexible rubber gasket. With the right gasket, the vent stack can move but will not loosen.

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Filling is also beneficial to keep away rodents from the pipes. You can fill the holes with steel wool, lath metal, metal heating, or hardware cloth.

Why It's Important To Seal Gaps In Your Home 

Sealing provides important protection against water and air leaks. You also keep rodents, insects, and other foreign objects out of the pipes. If you fill the gaps, you can avoid costly repairs. It is best to take action before the problems arise.

You should seal all the pipes and walls adjoining unconditioned spaces. When constructing your home, you should seal the gaps during plumbing works and before drywall installation.

There are a few reasons why you should fill gaps between pipes and walls. Read about them below.


Faucet, bathtub, and shower pipes meet the walls. In these areas, water is unavoidable, so you should protect the pipes by filling in any gaps. If not, water could get into the fixtures behind walls and on the floor. 

Water will encourage mold and mildew growth. If you have wooden fixtures, these are vulnerable to rotting.


Air leaking from the pipes will change the humidity levels in a home. Humidity affects energy use by retaining the warm, moist air on the walls. There will be problems when moisture condenses, like drafts that affect indoor air quality.

With sealed pipes, you also dampen the sound from the outside. When air passes through the right channels, there will be less sound.

Outside Elements

Pipes are the gateways of outside elements to your home. The temperature inside the pipes is enticing because it is warm. The most common unwanted outsiders are rats and insects. They can fit through pipes and work their way indoors. 

If sealing the gaps does not solve this particular problem, you should consult a pest control specialist. Considering the reasons given above, you should check the possible pathways outside and inside your home. 

Where To Check For Gaps

Pipes are located behind the walls of your home. If you suspect that some of them are leaking, you should find the exact pipe causing the problem. But locating the gap can be a challenge. 

You may need to do some drilling to fix the faulty pipes. If you drill in the wrong location, you can affect the pipelines and create bigger problems. 

Certified plumbers often use electronic pipe detectors. Plumbers add metallic tape when installing pipes, so that they are easy to detect. If there is no tape or anything similar, a good stud finder can be used to locate the pipes.

Here are some common places where gaps are located:

  • Under sinks
  • Around connections to washing machines
  • Leading to furnaces and hot water heaters
  • Inside bathrooms or laundry rooms

In Summary

copper and plastic pipes, fittings on concrete wall

With the right sealing materials, you can fill the gaps between pipes and walls. You can use caulk, expanding foam, or a flexible pipe gasket to fill the gaps. When filling, you should also account for insulation and the wall surface.

Filling the gaps is important, because water, air, and outside elements like rodents and insects can enter your house through openings. You should locate any gaps so that you can fix the problems beforehand.

The process of filling gaps may take time and effort, but it will help keep your home in good condition.

Learn more about pipes from these posts:

How Far Does Pipe Go Into SharkBite Fitting?

Sounds Like Water Is Running In My Pipes All The Time – What To Do?

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