What makes a door internal/external?

10 Dec 2009
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United Kingdom
Looking for a hardwood door as a replacment for a garge pedestrian access door and im wondering what classifies a door as internal or external.

Something to do with the construction?

Initially i thought any hardwood door should be good for external use but maybe not?
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External doors are generally 44mm thick, and internal doors 35mm

Internal doors are generally very flimsy, and may contain materials such as chipboard hidden under the veneer.

Lift a few up and you will notice the difference.
External doors are generally 44mm thick, and internal doors 35mm
In modern apartment housing it's becoming more common to find 51mm for externals (1 hour fire rated in, say, a block of flats with a communal entrance) and 44mm solid core internals. Whilst externals used to be solid wood or veneer-faced and edge lipped laminboard (strips of hardwood glued together) other core materials for exterior wooden doors are appearing such as MR chipboard and Accoya MDF

I wouldn't call a 44mm internal 30 minute fire rated door flimsy, either - try kicking your way through one and you'll see what I mean!

I agree that weight is a really good indicator of sound proofing properties

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