How to Fill a Gap Between a Foundation and the House

July 8, 2023

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Homeowners often wonder how to fill a gap between a foundation and the house. This is vital to understand! First, large foundation cracks risk interior moisture damage. Second, ignoring gaps and cracks lets them get worse, risking costly damage over time.

Homeowners should consult with a foundation repair contractor for larger cracks. For smaller cracks, you can use rubber cement sealer or polyurethane caulk for smaller gaps. Foam backer rods also help provide a watertight seal.

To find out more about how to fill a gap between a foundation and the house, keep reading! You only need a few simple tools to get this job done right. Also, some added information about foundation cracks can help you understand when to call a pro. In turn, you know your home is strong and stable from the ground up.

how to fill a gap between a foundation and the house

How to Fill a Gap Between a Foundation and the House

To fill the gap between a foundation and the house, you’ll need:

  • Polyurethane caulk or rubber cement sealer
  • Caulking gun
  • Foam backer rods and scissors
  • Chisel
  • Wire brush
  • Putty knife
  • Paint remover or mineral spirits
  • Rags
  • Protective gloves and eyewear

First, note that stores sell foam backer rods in long rolls, so you’ll need to cut them to size. Second, remember to snip the end of the caulk or sealer tube and test the gun before you start working!

Before filling the foundation gap, clean the area thoroughly with your wire brush and chisel. Next, use rags to remove all dust and debris, but wait until the surface dries before filling it. Your caulk needs a clean, dry surface to stay adhered to the foundation over time.

Gently press your foam backer rods into the gap. You can use your putty knife to wedge them into the crack thoroughly. Then, fill the joint with your caulk or sealer and use the putty knife again to push it into the gap. Clean your knife with the paint remover or mineral spirits and more rags as you work.

Lastly, use your sealer or caulk alone for very small or hairline cracks in the concrete. If the foam backer rod simply won’t fit into the gap, it’s probably not needed! Apply the caulk and press it in with your putty knife, to ensure a good fit. You can also use the knife to wipe excess caulk or sealer off the surrounding foundation material.

Should You Caulk Where Siding Meets Foundation?

Homeowners often assume that every gap along a home’s exterior needs caulking. This simply isn’t true! In fact, too much caulk can risk trapping water in various areas. Please note that you might do more damage than good by applying caulk excessively.

For instance, air circulation behind siding is vital. During freezing weather, ice often forms in that area and then expands. Caulking isn’t sufficient for blocking all water crystals and preventing this process! On the other hand, some air circulation can help dry those crystals, reducing damage risks.

Additionally, note that contractors and builders often use flashing to direct water away from various materials. Flashing refers to metal sheets designed to cover gaps and crevices along exterior surfaces. As an example, roofers apply flashing between shingles and chimneys. This creates a watertight trench that directs moisture away and protects those materials.

Consequently, homeowners don’t need to apply caulk around areas of flashing installation. You might notice this around window headers or other horizontal trim boards. If you’re unsure of when to caulk around your property, ask a repair contractor for advice!

how to fill a gap between a foundation and the house

The Best Caulk for Larger Gaps

To seal larger gaps in foundation concrete, start with your foam backer rods. Next, use expandable foam caulk over those rods. The expanding foam fills in those larger gaps and surrounds the rods completely. In turn, you can seal those gaps without having to use concrete fillers or mixes.

However, note that foam caulk does eventually break down and needs replacing. Consequently, homeowners should inspect their patchwork every year and note its condition. Once it’s broken down, chisel it out completely and perform the repairs again.

Can You Seal Concrete Too Much?

The short answer is yes, you can seal concrete too much! Overly thick sealant or too many layers create a damaging barrier against evaporation. In turn, you might trap moisture in the concrete, risking severe damage.

Additionally, note that concrete expands as it absorbs moisture and then shrinks as it dries. A contractor creates expansion joints, or trenches between concrete slabs, for this reason! Those trenches allow concrete sections to expand without pressing against themselves. Consequently, those joints reduce the risk of cracking and premature damage.

On the other hand, covering them or the concrete with too much sealant doesn’t allow room for that expansion. As a result, cracks might form under its surface. Rather than assuming that more sealant is better, follow a contractor’s or manufacturer’s direction. Their expert advice ensures strong, durable concrete that lasts.

What Do You Put Around the Foundation of a House?

Homeowners have several options when it comes to materials that they can put around the foundation of a house. These all help waterproof a foundation, ensure proper drainage, and help keep soil healthy.

  • A foundation repair contractor can install waterproof membranes around a foundation exterior. Membranes repel water, keeping concrete dry and secure. Additionally, keeping water away from the concrete helps ensure dry interior spaces as well.
  • French drain systems are an excellent choice for improving drainage around a home’s exterior. These start with small trenches just a few inches deep. Next, a homeowner or contractor installs PVC pipes drilled with small holes. Those pipes trap moisture from the soil and direct it away from the structure.
  • Gravel mulch is also a great choice for keeping soil healthy and a foundation dry. Crushed gravel protects soil from scorching sun while preventing it from “piling up” around the foundation. This reduces pressure on the foundation and helps plants and lawn stay hydrated as needed.
  • Rubber mulch is also excellent for protecting against foundation damage. Thick rubber offers added insulation, reducing cold air inside a space. Also, rubber helps repel insects, prevents weed growth, and needs little maintenance over the years!

Frequently Asked Questions

Are all concrete cracks dangerous?

Hairline cracks along concrete surfaces are not unusual. These result as concrete expands and shrinks during its curing process. However, cracks larger than 1/4” wide typically need immediate patching.

How can I tell if my home has foundation damage?

Weak foundations let a home sink along one side or the other, which pulls on solid surfaces and materials. In turn, cracks soon form along walls, ceilings, and other areas. Additionally, you might even notice countertops or floors suddenly sloping in various spots!

Also, crooked door and window frames mean doors and windows that stick or that don’t lock securely. Creaking floorboards and gaps in room corners can also indicate a damaged foundation that needs expert repairs.

A Word From Our Team

Grand Rapids Foundation Repair Pros is happy to help explain how to fill a gap between a foundation and the house. Hopefully, you found this useful! If you’re in the area, you can also call our Grand Rapids foundation repair team for expert services. We’ll get your property started with a FREE inspection and repair quote, so contact us today.


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