Shorten a prehung slab door? Top or bottom?

[MatBirch]

As luck would have it, a buddy just bought a house and replaced all his interior doors. He gave me his garage-to-interior fire rated door with jamb for my shed.
I need to cut it down about 4” though to fit. The frame has an extruded aluminum threshold on the bottom. I should be able to cut either end and reassemble.
Is there a more “accepted” way?
If I cut the bottom, the knob gets lower... I guess that wouldn’t be bad, as there is a step up into the shed.

 

[Bill Wright]

If you cut the door it looses its fire rating.
If you don’t care cut the bottom.

 

[Kaizen]

I’d change the framing if possible. Easier then cutting a metal door.


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[MatBirch]

Door’s not metal, it’s melamine covered, something solid. Definitely don’t care about the fire rating. Shed is a tinderbox built from pallets! Lol.

 

[The Cobbler]

I would cut the top in that case .
just remember it might not be exterior rated,and thus have a short life

 

[p00p]

idk if it matters, but if cutting effects the hinged areas, I'd try to not make more work regarding that.

 

[PCustoms]

That's a lot to cut, what's the opening framed for?

I usually cut the bottom, so you don't have to mess with the top casing, but that's usually enough to clear a floor. 4" is going to put the lockset in an odd spot.

2" off each end?

 

[The Cobbler]

I suspect hes got a r/o for 6'8" and the door is 7'0", and comment about lockset is partly why I suggested the top

 

[MatBirch]

RO is what I make it... but I’m limited to 81-1/2” due to the overall height of the shed. Fortunately it’s very dry here, so I’m not to worried about it lasting in the weather. I’ll seal up all the edges well, and the face is plastic. Should last a good long while.
I’ve had a chance to look it over more, and it looks like the top may be easier to cut. I think I can just pop the staples holding the top of the jamb off, cut the sides to length, rabbet, and screw it back together. The threshold seems to be more troublesome with additional rabbets.

 

[captain14]

If you can, build an overhang or small porch roof over the doorway. This will help keep the door and framing dry to prevent premature rotting out. Prime and Paint all the wood too. All 6 sides

 

[Viper98912]

In a shorter-ceiling height basement, I cut 1" to 1-1/2" from the bottom of the door with no issues, and cut the framing on the bottom to match. No issues. But this was an interior door. 4" is a lot - think about the lockset location relative to your entrance height from the outside (is your shed raised on a slab relative to the dirt?). You may need to cut a couple inches from both sides.

 

[yeldogt]

Some of those fire doors have gypsum and vermiculite in them --- can you see who made it to google and see what's up?

Typically a door will have a little space to trim on the bottom and none on the top -- Fire doors are not typical and since they can't be altered and still be rated ...may not have any adjustment areas.

Some are full wood doors ....

My gut says you are going to cut into the core regardless -- maybe take a small drill and go in to see. Ideally taking some off the bottom so the knob is still at a reasonable height and they -- the rest from the top. Cap the top -- you can always cap the top of the door with metal and a small drip -- I do this with my wood gate doors

 

[mannydantyla]

I did this in my very old house with shorter than standard doors, and I cut the bottom. I got a solid oak door from Menards but unfortunitally it wasn't actually solid oak, it was oak vaneer and filled with particle board. So I coated the exposed particle board with several layers of shellac. This is for an exterior door for my back sunporch. And the door itself isn't made for exterior, it's interior only. We'll see how long it lasts lol.

Also notice how the bottom cut on the door had to be at an angle, that is because the sunroom is all crooked. I think it used to be a deck and a previous owner converted it to interior space and it never really had a real foundation so it once side sunk a little, causing the whole room to be crooked. I would jack up that corner myself but that is another story.

Oh and if the pic looks like the stain is darker on the bottom than the top, that's because it is. Always remember to shake/stir your can of stain. (I was using Rubio Monocoat exterior stuff.)

 

[stroked93]

Cut the top or the door handle will be too low.

 

[Daniel Dudley]

RO is what I make it... but I’m limited to 81-1/2” due to the overall height of the shed. Fortunately it’s very dry here, so I’m not to worried about it lasting in the weather. I’ll seal up all the edges well, and the face is plastic. Should last a good long while.
I’ve had a chance to look it over more, and it looks like the top may be easier to cut. I think I can just pop the staples holding the top of the jamb off, cut the sides to length, rabbet, and screw it back together. The threshold seems to be more troublesome with additional rabbets.

Sounds like a plan.