Window Installation and Replacement

Whether or not a building permit is required for installing or replacing a window depends on what kind of structure the windows are going into and what kind of alterations are involved.

Code requirements come from the International Building Code (IBC), International Residential Code (IRC), Washington State Energy Code (WSEC) and the current Kirkland Municipal Code (KMC).

STEP 1 - Determine what kind of structure the windows are going into

There is a difference in requirements, depending on whether the windows are in an IRC or IBC structure.

IRC Structure = Single Family Residence, Duplex, or Townhouse 

IBC Structure = Structure other than those listed above (such as office, condominium, restaurant, etc.)

STEP 2 - Determine if a building permit is required

For windows located in an IRC structure:

KMC 21.06.215: A building permit is not required when replacing an existing window in an IRC structure as long as no alteration to any structural member is required. 

NOTE: Even when a building permit is not required, the window related code requirements listed below must still be met. Skip to Step 4.

A building permit is required when installing a window where none was present, and when replacing an existing window if any structural alterations are necessary (such as when a larger header is required to be installed because the replacement window is wider than the original window). Skip to Step 3.

For windows located in an IBC structure:

There is no situation where a window installation or replacement in an IBC structure is exempt from requiring a building permit. Go to Step 3.

STEP 3 - Apply for a building permit

When applying for a permit: 

  • A Site Plan shall be provided to show the location of the exterior wall(s) where the window(s) are to be installed or replaced.
  • Building Elevations that are modified due to window installation or replacement shall be provided.
  • Floor Plans shall be provided to show what room(s) the window(s) are located in (such as bedroom, dining room, garage, etc.)
  • Notes and details showing compliance with the window code requirements identified in Step 4.
  • Any structural modifications and framing members must be identified on the plans (headers, posts, shear walls, etc.).
  • Other building permit application requirements can be found on the Building Permit Checklist.


Apply for a permit

STEP 4 - Window related code requirements

Note: For IBC structures, consult the IBC for specific code requirements.

For IRC structures, the following code requirements shall be met:

  • If the window is located in a basement or sleeping room that doesn't already have an emergency egress window, the new window must meet “emergency egress and rescue opening” requirements where feasible. See Construction Tip Sheet 10.
  • If the window is in a “hazardous location,” the window must be made of safety glazing. See Construction Tip Sheet 19.
  • The new or replacement window shall meet the WSEC requirement for U-value. Prescriptively, each new window shall have a maximum U=.30. Otherwise, when multiple windows are installed, together they shall have an area weighted average of no more than U=.30.
  • Fall protection shall be provided on any operable window that requires it. See Construction Tip Sheet 23.
  • When infilling an existing wall where a window used to be (in a heated space), the wall shall be insulated.
  • For a 2x4 framed exterior wall, R-15 insulation shall be used. For a 2x6 framed exterior wall, R-21 insulation shall be used.