One of our many projects last year was to replace our back exterior door. It is in a converted porch, unfortunately, which means it's an odd size.

Specifically, it's 75-76" x 30". Unfortunately, none of that is negotiable - more than 30" and the door opens over the steps to the basement, and more than 76" and the jamb would be cutting into the structural supports. It's also not straight, because the porch has a bit of a lean to it.

Last year, we bought one of these, a 30x80 composite wood door, from Home Depot. We cut it down to the requisite size - managed to do a decent job of that, amazingly - and installed it.

Unfortunately, despite being an "exterior" door, the wood started peeling almost immediately. This is Northern Illinois, so a bit harder on doors than warmer locations, I suspect.

The question is, what options do we have here? What's our best bet to get something that will last at least a few years? I suspect eventually we'll take out the porch and make improvements to extend the whole house back some - our house is the shortest in the neighborhood in terms of how much of the lot is used by the house itself - but that's 5-10 years down the road at least.

  • Buy another slab, cut it down again, and try better finishing options.
  • Buy a steel slab, like this one, and cut it down - but can you cut a steel door like that?
  • Find an all-hardwood slab door that can be cut down (do these exist?)
  • Something else?

Is there a "best" approach here that doesn't involve a few grand for a custom door? Is that the only real solution to this kind of problem that won't need replacement every year or two?

  • And - yes, we've tried the reclamation stores in the area (several times in the last few months). No luck at all.
    – Joe
    Oct 19, 2015 at 17:46
  • With that door you bought, did you finish it? (Paint?)
    – DA01
    Oct 19, 2015 at 18:08
  • Just a seal, which clearly wasn't enough by itself. That's part of the question, I guess - if we paint it or apply something more, will that be enough for the slab? Or does it need something stronger for the bad weather/moisture/etc.
    – Joe
    Oct 19, 2015 at 19:26
  • A good exterior paint will likely be the ideal finish for that type of door. Also, are you using a storm door? If so, check if the door's warranty is void if you use a storm door. Storm doors, especially if they face the sun, can super-heat the interior door to the point of failure. (Alternatively, though, doors that can handle a storm door benefit from the extra barrier to the water.)
    – DA01
    Oct 19, 2015 at 19:31
  • No, there's no room for a storm door (without building out).
    – Joe
    Oct 19, 2015 at 19:33

5 Answers 5


Some suggestions:

  • Regardless of the door type, a good coat of primer and exterior paint will be the better of the finishing options.

  • a fiberglass or steel surface should outlast a wood one (they should both be 'trimmable' with the right saw blade)

  • Check to see if your door slab could benefit or be harmed with the inclusion of a storm doors. Some doors benefit (water protection) other's can be damaged by it (over heating in the sun).

  • consider ripping out the entire door and door jamb and installing a whole new all-in-one pre-hung exterior door. This will allow you to re-square up the opening and also likely give you the most water-tight seal.

  • I don't think pre-hung is an option, unfortunately. I don't find many 75" pre-hung options, and even if it were, our hinges are attached to the other wall (so no door frame on the hinge side) due to space. Sigh.
    – Joe
    Oct 19, 2015 at 19:44
  • As far a steel - I'm not worried about cutting through it, but are steel doors made in such a way that it's okay to trim 5" off of them (either 5" on one side, or more likely 2" off the top 3" off the bottom)? We're worried there are structural elements we'd be gutting.
    – Joe
    Oct 19, 2015 at 19:45
  • @Joe oh, yea, just had a 'doh moment. I was thinking it was the width that was odd, but it's the height. As for exterior doors, that's a good question. There's usually a solid frame and several inches at top and bottom before you'd get to the 'hollow' part (that's usually full of insulation on exterior doors). You may just need to call up the particular manufacturer of each door to ask.
    – DA01
    Oct 19, 2015 at 22:51
  • I'd be very cautious about trying to cut down a steel or fiberglass door. You should be able to find a solid core (not particle!) door and cut it down without having it fall apart. This assumes adequate paint/sealing. And JeldWen doesn't have the best rep for some of their pvc products, so I wouldn't be surprised if this lack of quality leaked over into their doors. Oct 20, 2015 at 1:26

Have you considered a GRP composite door? It may not fit with the style of your house, and I don't know availability in the US, but I bought myself a custom made one online for £600, and self-installed it. That's about $1000, rather than the "few grand" you are expecting a custom door to cost.

  • Is that the UK name for Fiberglass? (I search GRP Composite and find only UK sites, but wiki for Fiberglass indicates Glass Reinforced Plastic is another name for that.) That's an interesting thought, it's still sort of expensive but not as much as custom wood.
    – Joe
    Oct 20, 2015 at 15:27
  • @Joe - I guess so, yes. When I hear fibreglass I think of this rather than the nice finished texture of my front door. But then, thinking about it further, my bath is nice and smooth inside but has the texture of my linked picture if you take the side panel off and look underneath.
    – AndyT
    Oct 20, 2015 at 15:59
  • Hmm. I don't see that fiberglass is particularly cheaper here - will have to look more into that, but all of the quotes I'm seeing for custom fiberglass are $5000+.
    – Joe
    Oct 20, 2015 at 16:18

Yes, you can cut down a steel door smaller, but I would not call it simple. I have a steel door from Home Depot similar to the one you reference, which I shortened by half an inch.

I would only attempt to change the height of a steel door like this by a small amount; no more than an inch or two. 5 inches height change would require some major reconstruction. And I would not attempt changing the width, due to the way the steel is bent and fits into a slot in the wood.

All the steel doors I've seen are constructed similarly. There is a wooden frame inside, making up the top, bottom, and two edges. And there are two steel skins attached to the wooden frame, for the two faces. They are bent over around the edges and press fit into the wood. The top and bottom are just 90-degree bends, but the side edges are bent into a "U" or "J" shape that fits in a slot in the wood frame.

On my door, I carefully unfolded the bottom edge of the steel, pulled out the wood bottom frame piece, cut it shorter, and trimmed half an inch off the steel sheet metal using shears. Then I replaced the wood bottom, and carefully folded over the steel to wrap around the wood. It was slow and fussy to get it even, and it still warped and buckled a minor amount. Fortunately none of it is at eye level.

The wooden frame inside the door is a few inches wide, so if you want to trim off 5 inches, it will require peeling back the steel to reconstruct the wood frame. Since the steel is folded on 4 edges, it will want to kink and buckle a fair amount on the sides.

I would recommend getting a steel or fiberglass door only if you get a custom door made to size. If you're going to cut one down, use a solid wood door.

Definitely look into repainting your existing door with a better primer and paint. Instead of latex or acrylic, look at oil-based or alkyd paint, such as Rustoleum, which will stand up to weather better. Yeah, it smells worse and is more trouble to clean up, but for only one door it is worth the trouble.


Simply special order the right sizes for a rough opening. If you can start fresh, wait a week or two and get a good fit that will last. You can cut like a consumer said if need(if its your property, and you're OK with it). If you're an installer its not recommended.


Just did a similar fix on a split level basement exterior door with concrete walls and 7 foot ceiling. bought a pre-hung fiberglass and trimmed the frame width so the door sits against the inside wall but the threshold sits out to the edge and the door is taller than the opening so it almost touches the low ceiling on the inside. Attached 4x4s to the wall using concrete anchors on each side of the door jamb. attach the jamb to the 4x4. Painted it up and looks cool.

The door opens and thee exterior height is only showing a few inches so painted that piece of concrete to remind me that its lower than the door opening.

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