The Garage “Bump Out”: Adding a Mudroom Without Losing Parking Space

A garage bump out can add a functional mudroom by extending the garage wall outward 3 to 4 feet, so you keep your original parking space. Because it’s a structural addition, it needs a frost-protected foundation, proper load-bearing support, and a roof tie-in that matches the house.

Why Homeowners Want a Mudroom in the Garage

For many Salt Lake Valley homeowners, a mudroom is a daily necessity. It gives you a durable transition space to drop muddy hiking boots after a weekend in Millcreek Canyon, hang heavy ski jackets, and store wet gear before it reaches clean floors.

The problem is that many older or standard single-family homes do not have extra interior space to give up. The garage often seems like the best place to add a mudroom, but even a small change inside the bay can make parking impossible.

A garage bump out solves that problem by pushing the exterior wall outward by 3 to 4 feet. That creates a usable mudroom without taking away a full vehicle parking space.

The Foundation Reality: Frost Protection Matters

A small bump out cannot simply sit on a shallow concrete pad. In the Salt Lake Valley, any structural addition attached to a home needs to be protected from frost heave.

Along the Wasatch Front, the minimum frost depth is 30 inches.

When the soil freezes, it expands. If the new foundation is too shallow, the addition can move while the rest of the house stays put. That can lead to:

• cracked drywall,
• sticking doors,
• and roof leaks where the addition connects to the home.

What this means for your mudroom:
Even a small bump out needs a proper foundation that goes below the frost line, not just a surface slab.

To build a code-compliant addition, the site must be excavated to at least 30 inches, then reinforced concrete footings and a foundation wall must be poured to connect properly with the existing house.

Opening the Load-Bearing Wall

To connect the new mudroom to the garage, the existing garage wall has to be opened up. Since exterior walls usually carry roof loads, they cannot be removed without structural support.

Before any studs come out, a temporary shoring wall is installed to support the roof. Then the wall opening is framed with an engineered multi-ply LVL header beam that carries the roof and truss loads above the opening and transfers them safely down through trimmer studs to the foundation.

What this means for your garage:
If you want a mudroom connected to the garage, the opening needs engineered support, not just a simple cut in the wall.

Matching the House Exterior

A high-end bump out should look like part of the original home, not like an afterthought. That means the roofline, siding, and weather protection all need careful planning.

Managing the Roof Tie-In

Depending on your home’s layout, the new mudroom roof may need to:

• extend the existing garage slope,
• or use an engineered gable or shed-roof tie-in.

The roof valley where the old and new sections meet should be protected with:

• ice and water shield,
• custom metal flashing,
• and properly detailed shingles.

This helps prevent snowmelt from pooling and backing up under the roof during Utah winters.

Matching the Exterior Finish

The addition should match or complement the home’s existing exterior materials. Whether the house has:

• brick in the Avenues,
• stucco in Sandy,
• or fiber cement siding elsewhere,

the bump out should use the right weather-resistive barrier and finish materials to keep the exterior durable and visually consistent.

What this means for your home:
A mudroom bump out should blend into the house, both structurally and visually.

Setbacks and Planning Ahead

Before breaking ground, the new footprint has to be checked against local zoning rules. Even a 3-foot extension can cause problems if the house already sits close to the minimum front or side setback.

Planning early helps avoid costly changes later in the project.

What this means for your project:
A bump out may be small, but it still needs to fit your lot, your setbacks, and your existing structure.