An inner frame post is the inner stile of a window or door frame, the vertical member on the interior side of the wall. It forms part of the frame assembly that holds the window sash or door leaf, and it is positioned on the side of the frame that faces into the building.
Role in frame construction
A window or door frame consists of several parts: the head (top horizontal member), the sill (bottom horizontal member) and the stiles or posts (vertical side members). When a frame is set into a wall, one stile faces the interior and the other faces the exterior. The inner frame post is the stile on the room side.
The inner frame post has several important functions:
- Hinge or latch mounting — Hinges, locks and handles are often fitted to the inner frame post, depending on which side the door or window opens.
- Seal and draught prevention — The inner post carries weather seals and draught strips that press against the door leaf or window sash when closed.
- Rebate profile — The post includes a rebate (a stepped recess) into which the door or sash closes, creating a tight fit.
- Finishing surface — On the interior side, the inner post is visible as part of the room’s trim and is usually painted or stained.
Differences from the outer frame post
The outer frame post faces the exterior and is exposed to rain, wind and UV radiation. It therefore requires more robust weather protection, such as hardwood timber, aluminium cladding or factory-applied coatings. The inner frame post, being sheltered inside the building, is subject to less weathering but must still be properly finished to resist indoor moisture, particularly in wet rooms like bathrooms and kitchens.
In traditional timber construction, both posts are cut from the same piece of wood. In modern composite frames, the inner and outer posts may be made from different materials — for example, timber on the inside for a warm appearance and aluminium on the outside for durability.
Related terms
- Frame
- Outer frame post
- Stile
- Door
- Window
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