Your building

The house has an attached garage

“Does the attached garage affect the radon reading?”

An attached garage matters for indoor air quality, but mostly for reasons other than radon: vehicle exhaust and stored chemicals move into a house through a shared wall far more readily than most people expect.

For soil gas specifically, a garage slab is another slab in contact with soil, and where the garage shares a wall or a floor plane with the house it can be part of the picture.

Why this matters

What it changes about the decision in front of you.

A garage slab is in contact with soil like any other, and the wall between garage and house is frequently less well sealed than an exterior wall.
Pressure differences between garage and house can move air in either direction depending on ventilation.

What it could influence

Where the effect is likely to show, and in which direction where that is knowable.

Where a garage adjoins occupied space over a shared foundation, entry there may contribute.
Measurement is generally not taken in a garage, so it is not usually part of the reported figure.

What this does not settle

What still stands. Noticing a problem is not the same as losing the evidence.

An attached garage is not a radon finding and does not indicate elevated levels.
This is worth keeping distinct from the soil-gas question rather than folded into it, because conflating the two confuses both.
It does not establish that garage air is entering the house.

What a professional is likely to ask

Worth having answers ready. None of these is a test you can fail.

Whether the garage shares a foundation plane with occupied space.
Whether the connecting door and wall are sealed and whether the door self-closes.
Whether anything is stored there that matters for indoor air generally.

What you can check yourself

Things you can establish today, without anyone visiting.

Whether the garage is at the same level as occupied space or below it.
Whether the connecting door seals and closes on its own.
Whether there is living space directly above the garage.

What genuinely needs somebody on site

Where this platform stops. These are not questions a website can answer about your house.

Whether the garage and house foundations communicate, which is not usually visible.

Categories a next step could fall into

Unordered, and none of them is a recommendation. Which applies depends on things this page does not know about your situation.

Request a professional assessment

When it is considered. When the building itself is part of the question — foundation type, an existing system, access, or an unusual layout.

What it would establish. What the building is doing, which no amount of information typed into a website can establish.

Review the testing context

When it is considered. When the conditions, placement, or duration of the test are unclear, which is the most common situation and the cheapest to resolve.

What it would establish. Whether the existing result is something to reason from, or something to repeat under conditions that can be described.

Sources

U.S. EPA — Consumer’s Guide to Radon Reduction

When you are ready to talk to somebody

Tell us about your home and what you are trying to work out. We will tell you honestly whether we can route it to a provider in your area today.

Start a request