When designing a home, it's easy to overlook details like door frames. The frame can be vital to the longevity of your door’s life though, as this is what the hinges will be attached to. Likewise, it can affect how much heat enters or escapes your home.
A weak frame not only presents a security hazard, but will also deteriorate faster, loosening at the hinges and causing your door to stop doing what it's supposed to do. Getting the frames installed properly and with solid materials should be as important to you as the type of door and materials you choose to go with.
Interior and exterior frames will have different requirements; your exterior door frames will need to be a lot tougher than your interior ones, not only because of the potential security risks a flimsier frame would pose, but because of the constant weather exposure.
For exterior frames a nice, solid long-lasting wood like white oak will keep its appearance throughout the years, and can withstand a lot of punishment. The wood is also very easy to stain or paint, giving it added flexibility. Alternatively, for exterior doors you might consider a steel frame to add a huge layer of security to your door.
Interior frames aren’t subject to the same weather conditions and security concerns, so can be made of cheaper wood such as pine, or whichever shade or texture of wood best suits your décor. The worst punishment your interior door frames are likely to see is from kids hanging off doorknobs.
Pre-hung doors vs. slab doors
Most manufacturers offer pre-hung doors these days - that is, doors that come already hinged and attached to a frame. The advantage of this type of door is that it's already very tightly fitted - and if you're building a home from scratch, this can help ensure a quick, easy and secure installation. Pre-hung doors may also be a better alternative if you're replacing an exterior door - to ensure that the final product is nice and secure - or when you're looking to replace a door with a damaged frame.
The alternative is to buy a door and frame separately. A door on its own (i.e. without a frame, hinges or any door furniture installed) is simply called a 'slab door'. A slab door on its own is cheaper than a pre-hung door, but you're obviously not paying for a frame or hinges either. If you're replacing a damaged slab door and you're able to find one that has the exact same dimensions, that's likely to be the easiest route because you'll already know it's a good fit. Replacing a frame is normally a different matter altogether.