Window replacement is one of the more common home projects and one of the less complicated from a permitting perspective — with two genuine exceptions.
Like-for-like replacement
Replacing windows in existing openings at the same size frequently does not require a permit, though this varies by jurisdiction and it is worth confirming for your address.
What does still apply is the energy code. Washington’s requirements exceed the national baseline, and replacement units must meet current standards. Practically this means the windows going in will typically be a specification step up from what came out, which is a requirement rather than an upsell.
Changing the opening
Altering the size of an opening is structural work and generally requires a permit. Enlarging an opening affects the header carrying load above it; that is an engineering matter rather than a carpentry preference.
This includes converting a window to a door, adding a new window where none existed, or enlarging an existing one — all common enough in remodels and all needing to be planned as permitted work.
Egress: the one that matters most
Bedrooms require a window meeting egress requirements — an opening large enough for a person to escape through in a fire, and for a firefighter with equipment to enter through. There are minimum dimensions for the clear opening and maximum heights for the sill above the floor.
The practical trap is subtle. Replacement windows have frames, and an insert window fitted inside an existing frame has a smaller clear opening than the original. A bedroom window that met egress before replacement can fall below the requirement afterwards, purely because of the frame thickness.
A competent installer checks this. It is worth asking about explicitly for any bedroom window, because the consequence is a compliance problem that surfaces at sale, and a genuine safety reduction in the meantime.
Basement conversions
Converting a basement room into a bedroom brings egress requirements into play directly, and basement windows frequently do not meet them as built.
Achieving compliance usually means enlarging the opening and often installing an egress well outside it — a substantial piece of work involving excavation, structural alteration and permits. This is one of the most common ways a basement bedroom project turns out considerably larger than anticipated, and it is far better identified at planning stage.
Historic and design review
Some Seattle neighbourhoods and certain structures elsewhere carry design review or historic requirements affecting what may be installed. Where these apply they can rule out products that would otherwise be quoted, so establish early whether your property is affected.
Practical checklist
Confirm whether a permit is required at your address. For any bedroom window, confirm the replacement maintains egress compliance. If converting a basement room to a bedroom, establish the egress position before budgeting. And check whether design review applies before selecting products.