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The closets in my house all have sliding, 6-panel, masonite-style hollow doors. The house is 20 years old.

It seems all the available doors are 30" x 80". The one I need to replace measures 30" x 78 7/8".

My guess is that the builder did not spend money having custom doors made. Instead, they framed the closets for 80 inch doors then trimmed standard ones to allow for the space taken by the top rails and rollers.

Is there any way to get a door made to size? Or do I need to cut down a standard door from the home center?

If so, how thick are the rails at the top and bottom of the door? I'm concerned that removing a full inch from the top or bottom may weaken the construction (especially at the top where I need to attach the rollers).

Also, what type of saw would you use? I can't imagine formed masonite will cut cleanly (i.e. lots of tearout).

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  • The reason for getting new doors? 20 years not old enough for them to break down from normal use. Agree that cheap hollow doors might be pushing it if need to trim. Are you should it masonite?
    – crip659
    Commented Mar 5, 2023 at 21:16
  • There are mfgrs of prehung doors made for a specific rough opening. The door opening must be measured properly for a prehung door to fit in the rough opening. Aside from the obvious height and width you must make sure the sides of the rough opening are close to plumb. If they are too far out of plumb, then the width measurement will be incorrect. Commented Mar 5, 2023 at 21:50
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    @crip659 The room was used by my kids for 20 years as they grew up. Popped off the rollers multiple times, dragged open and closed instead of asking us to put them back on the rails. General wear and tear. Now the top panel on the door is basically trashed (all the molded texture worn off). Just time to replace this one.
    – kdopen
    Commented Mar 5, 2023 at 22:26
  • @crip659 And yeah, pretty sure they are masonite. Way too lite for a solid core door, the "raised panels" are identical on every door (i.e. they are formed/printed), and I can see the subtsrate where it's been worn away on the existing one..
    – kdopen
    Commented Mar 5, 2023 at 22:32
  • Thanks all - now I don't know which answer to accept :( RMDMan's seems more complete, but Ruskes' has that killer studfinder suggestion
    – kdopen
    Commented Mar 5, 2023 at 22:34

5 Answers 5

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Hollow core doors have a solid wood border you can trim.

How much ? depends on manufacturer.

However you can find out how much is safe to cut off.

Use Stud finder to find out the dimensions of the inside solid wood border.

Some border are only 3/4 inch

Since you already know the correct dimension of 78 7/8" that is what you have to cut the door too. Since the bottom of the door has no function, cut it from the bottom, while leaving the top intact so it is strong enough to carry the weight.

As for the saw, the more teeth it has the finer the cut.

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    Thanks for the stud finder suggestion ... one of those blindingly obvious ideas that just never occurred to me.
    – kdopen
    Commented Mar 5, 2023 at 22:29
  • @kdopen you are welcome, now you know another helpful trick
    – Traveler
    Commented Mar 5, 2023 at 22:41
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    I once had to trim a door more than the border covered. It wasn't that big of a deal; I just had to glue the border piece back into the door cavity. Since it was on the bottom of the door, it wasn't even visible once the door was hung.
    – spuck
    Commented Mar 6, 2023 at 17:11
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    @kdopen I may have mixed up the terminology. I thought I've heard it referred to that way but it doesn't matter. For table-saws, I understand the idea to be more of a safety feature that prevents things from falling into the blade well (unsure if that's the the right term.) This guide turns your cicular-saw cuts from eyeballing a line to a dead-straight and perfectly accurate cut as long as you take the time to position the jig properly and clamp it securely.
    – JimmyJames
    Commented Mar 7, 2023 at 17:32
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    @JimmyJames I did read most of the first article. I understand you make it yourself. This is still a form of manufacturing, and more to the point, is still subject to the basic concept of tolerance. Likewise, anything you make with it will have a tolerance. In fact, for an average DIY user I would image the achievable tolerance would be worse than from someone who does it every day, 8 hours a day. Also, wood is horrible for tolerance in general. If you want tight tolerance use metal. But again, it would still be non-zero.
    – cat40
    Commented Mar 8, 2023 at 4:00
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If you buy from a real door shop (not a big box), they will be able to tell you how much wood is in the border. Usually, pay more means get more.

If it was me, I’d leave the top alone. (Aesthetics, mostly: the width of the side stiles is equal to the width of the top rail. Lopping 1/2” of upsets this relationship.)

Unless you know you have a border of at least 1-1/2”, plan on using the offcut from the bottom to stuff back into the bottom of the door. (Peel/scrape the Masonite skin; use glue and clamps.) As others have noted, clamp something straight to use as a guide for your circular saw. 40 teeth in a blade will yield good results. To help with tearout on the Masonite, lay painters tape on both sides of the door on the cutline, though the bottom is less important.

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You can take exact measurements to your home store and they should be able to order them for you. I had custom panel bi-fold doors made to replace some old metal ones. I wanted solid doors to insulate the Air handler. They were about three times as expensive but boy did they work well.

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I have cut the bottom of a hollow door to find there wasn't enough bottom rail, leaving me with a door with an open bottom. I carefully ripped some pine to fit and glued it in to fill the gap. After a coat of paint it looked better than the original and I was good the go. I ended up doing several other doors the same way.

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The size of the rails depend on manufacturer,

However you can reasonably cut 1/2 inch from the bottom and top of hollow doors.

A circular saw with a fresh,sharp, thin kerf blade will do the job.

Use a guide rail or at minimum, a known straight board clamped to the door.

Cut with the inside (less seen) side of the door up. A sharp blade leaves little tear-out.

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  • Thanks. I took some more detailed measurements. They had clearly cut the inch off the bottom of the door as the top panel matches those on my full height doors, but the bottom panel is 1 inch shorter.
    – kdopen
    Commented Mar 5, 2023 at 22:28
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    Cutting a full inch can be iffy. But if needed you can remove the facing material and glue the wood "plug" back in.
    – RMDman
    Commented Mar 5, 2023 at 23:02

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