Addition and ADU Structural Design in Beaverton, OR
A large share of Beaverton addition work is now accessory dwelling units, and the two common routes have almost nothing structurally in common. A detached ADU is a small new building and is largely a straightforward design. A garage conversion is a change of use on an existing structure, and that is where the engineering questions actually live.
Garages are built to a lower standard than living space in ways that matter once someone lives there. The slab is typically thinner and rarely insulated or reinforced for a floor. The framing over a garage door opening was sized for a garage door header, not for the loads a converted wall assembly imposes. And filling in that opening changes the lateral behaviour of the whole wall line, usually for the better, but only if it is framed as a real wall.
The foundation is the item most often overlooked. A garage slab commonly has a thickened edge rather than a proper frost-depth footing, and converting to habitable space can require underpinning that perimeter — which is far cheaper to know about at design than to discover during inspection.
What We Look At Here
- Existing garage slab thickness, reinforcement and edge condition
- Whether the perimeter has a code-depth footing or only a thickened slab edge
- Header over the garage door opening and what it will carry once the wall is filled in
- Lateral capacity change from infilling the opening, and how it is framed
- Roof and ceiling framing against the loads of habitable rather than storage use
- For detached ADUs: foundation design for the site and separation from the main house
More on the service itself: Addition & Remodel Structural Design. More on the area: Beaverton.
Questions
Frequently Asked Questions
Can my Beaverton garage be converted to an ADU?
Usually, but the foundation is the item to check first — garage perimeters often have a thickened slab edge rather than a code-depth footing, and underpinning is much cheaper to plan for than to discover during inspection.