How to Cut and Resize a Steel Clad Entry Door

We purchased a house in 2011. When we moved in, the front door wouldn't open all the way; it drug the floor at about 70 degrees from full open. Enough to squeeze by it, and you could force it all the way open, but it was rubbing the floor pretty good. I figured this was an easy fix and didn't pay too much attention to it. A few weeks after living there, I realized that the reason the door was dragging was because the door was not plumb. The top of the jamb was leaning into the house, so as you opened the door, the knob side of the door swung downward as well. I devoted some time to remedy that situation and quickly realized my next hurdle.

Now that the door was plumb and would swing all the way open, I also realized that the bottom seal/weatherstripping was missing from the door. The "new" hardwood floors (installed prior to purchase) were great, but the person that installed them failed to realize that the thickness of the flooring would impede the ability of the entry door to seal properly. Low and behold, the reason is because the threshold is lower than the floor height. So for two very cold winters we have had a large gap under our front door. We plug it with draft stoppers, towels, etc., but it still lets in a ton of cold air. I decided that this winter would be different so I started researching my options.

In most cases, it's easier to raise the header and keep a standard door size, but the soffits on the front of my house are directly above the door frame, so I have ZERO room to go upward. I need a door that is approx. 1 1/2" shorter than the standard height and I can build up my rough opening from the bottom. I priced doors from everywhere in town, and they are all special order ranging from $450-$700 for a basic, 6 panel, steel clad door. Keep in mind that a basic, 6 panel, steel clad door can be purchased at any home improvement store for just over $100. So, we're looking at $300+ to cut 1 1/2" inches off??? No thanks. After researching off and on for a while, I decided to tackle the project. Follow along if you're still interested.

Step 1: Gather Tools and Supplies

You'll need a variety of tools to complete this task exactly as I did it. Some tools may be substituted for others, this is just what I used. Note: you will NOT need a torch to complete this task. :)

Tools:

• normal hand tools - screwdrivers, pliers, hammer, etc
• drill
• router with straight bit
• circular saw
• reciprocating saw
• utility knife
• air compressor
• air stapler
• straightedge (at least as long as the door is wide)
• square
• pencil
• caulk gun
• sawhorses
• clamps

Supplies:

• replacement steel entry door
• Liquid nails
• 1 1/2"-2" staples
• scrap wood

After some research, I purchased my door from Menards for two reasons. The first is because they regularly go on sale for $119. Second because I think it is a better built door. The doors are made by Midwest Manufacturing, who has a door comparison here. I assume competitor H and competitor L refer to Home Depot and Lowes, but that's only an assumption. I do have experience with the Reliabilt brand door from Lowes, and my opinion is that this Menards/Midwest MFG door feels like a better built, heavier duty door.

Step 2: Prep the Door

This process will be done in two parts - cutting the door and then cutting the frame to match the cut door. Before you begin, remove any fasteners that hold the door into the frame during shipping. This door was held in by two small nails through the lock side frame into the side of the door. Remove the hinge pins and remove the door from the frame.

Lay the door on the saw horses. You may want to use towels or pipe insulation or carpet scraps, etc over the sawhorses to prevent scratches. This door came primed, but need to be painted anyway, so I just used some cardboard over the sawhorses. If your door is pre-finished take extra care to prevent scratches.

Next, determine exactly how much you need to remove from the door. I measured down from the top of my existing door and determined that the bottom of the door needed to be 1-3/8" shorter to allow room for the door to swing open and clear a doormat on the floor.

Back to the new door, remove the bottom weatherstrip. It's just press-fit into the bottom of the door. It should pull right out, but if it's really tight, gently pry it off with a screwdriver or narrow putty knife. With the bottom seal removed, you can see how this door is constructed. The sides of the door are wood, while the top and bottom rails are composite (i.e. plastic). The steel "skin" of the door is folded/crimped under the door and around the side rails. This is what is referred to as a "thermal break". The steel skin exposed to the outside temps would transmit some of that cold/hot temp to the inside if the inside steel skin was touching/connected to the outside skin. To prevent this, the manufacturers separate ("break") this thermal conductivity by means of dissimilar materials (i.e. wood/plastic/foam). Not all doors are manufactured this way, so it's something to keep in mind when purchasing a door (see comparison chart link in step 1).

Now to mark where to cut. You'll make two marks on each side. Measuring from the top, mark how long you want the final length to be. Mined needed to be 77-5/8" so I marked this as my "FOLD" line. I then measured another 1/4"- 3/8" past the fold line for my "CUT" line to leave some material that can be folded under later on. This extra length may vary from one door brand to the next.

Flip the door over and mark the other side using the same method and measurements.

Step 3: Cutting, Gutting, and Plugging...

These doors cut very easily. While you may think that you need special equipment to cut steel, you don't...at least in this case. The steel skin on these doors is fairly thin. This door uses 0.022" steel, which is less than half the thickness of a U.S. dime.

I used a battery powered 5-1/2" circular saw (trim saw) with a standard blade. I set the blade depth just below the thickness of the steel. I was unsure how tall the bottom rail was and didn't want to risk cutting through it too. If you're cutting off more than 1-1/2", you could set your blade depth deeper than I did.

To gave my saw a guide to run against and keep the cut perfectly straight, I measured from the edge of the blade to the edge of my saw's base and clamped a straightedge to the door (see pic 1). Cut through the first side of the door, then flip and repeat.

NOTE: this method produces small steel shavings which fly everywhere. Use proper safety equipment - goggles, gloves, etc. I actually wrapped a bandanna around my face too.

Something to consider, especially if your door is prefinished, is a way to protect the door from scratches when pushing the saw across the door. Use masking tape or have a helper vacuum the shavings as you cut to prevent shavings from getting trapped between the saw base and the door. I ended up with a pretty long scratch on both sides of the door, but this door needs to be painted anyway.

With both sides of the door cut, you need to clean up the bottom rail to reuse. I found that a 1" chisel fit perfectly to scrape out the foam from the bottom rail. This door is injected with a polyurethane foam after assembly via a hole in the bottom rail. There is is thin plastic strip that acts as a one-way valve to keep the foam from coming back out.

Next is to remove some of the foam to make room for the bottom rail. You only want to remove foam to the proper depth so the bottom rail will be at the fold line. The easiest way to accomplish this is with a handheld router so you can set the depth and it be the same all the way across. I chose to use a straight router bit in a drill and do it by hand, constantly checking the depth of my cut (pic 6). If I do another door in the future, I'll use a router.

Test fit your bottom rail (pic 8) and mark where the wood side rails need to be cut down (pic 9). You'll also need to cut a little tab of steel off of each corner so the steel can be folded under the bottom rail. I used a recip saw to make these cuts (pic 10 & 11).

To trim the wooden side rails, I used a router, but because the surface that would support the router at this point is just two edges of steel, I needed to give a better support surface. I clamped some scrap wood to each side of the door to give the router a larger surface to ride on (pic 12). I set the depth of the router to cut so the wooden side rails would be flush with the bottom edge of the bottom rail once installed. In my case this was 3/8". Cut the wood rails and seal them off with some paint (pic 14 & 15).

To re-install the bottom rail, you need to use a solvent free adhesive to prevent it from eating away the foam inside the door. Just look at the label and see if it's safe for foam. Apply the adhesive liberally on all four sides of the door cavity (pic 17). Insert the bottom rail until it's fully seated against the foam. Use a rubber mallet (or hammer wrapped in a rag) to slowly bend the steel under the door (pic 18). Once the steel is bent under the bottom rail, flip the door over and repeat.

Finally, reinstall the bottom weatherstrip seal. You should have a near factory finish.

Step 4: Modify the Frame

Now it's time to modify the frame to match the new door. It is better to do this AFTER the door has been cut down, because you can adjust your cuts in case the door turned out a bit larger or smaller than you originally planned. Take the total amount you removed from the door and measure that distance up from the bottom of the frame. Remove any corner seals that may be along this cut line.

You'll need to remove the bottom threshold by gently prying and pulling the staples that hold the threshold to the frame. Mine used 2" long staples (pic 3). You can see the adjustable sill in this threshold. Not all doors have this, so keep this in mind when purchasing a door to cut down. An adjustable sill gives you a little error room if you don't get things cut perfectly.

Pull back the weatherstripping (pic 6). It's just a friction fit into a kerf (saw cut) in the frame. Use a square to mark the cut line on both sides of the board. Cut the bottom of the frame (pic 7). I used a recip saw, but any saw could be used. Be sure to save the scraps that you cut off. You'll need them.

Now that the bottoms have been cut, you'll notice that the door stop goes the entire length of the frame (pic 8). The stop needs to be cut away to allow the threshold to fit back in place. The easiest way to transfer the cut marks is to use the piece you just cut off as a template. They say a picture is worth a thousand words so see the animation (pic 9) for this process. With the angles marked, use a circular saw with the blade depth set to the thickness of the door stop, make a single cut through your marks (pic 10). Once the mark has been cut, make successive cuts BELOW the first cut. You can then break off the tabs with a gentle tap with a hammer (pic 11). Clean up the surface with a sharp chisel (pic 12). Put the weatherstrip back into place and trim to length (pic 13). Repeat on the other side of the frame.

The rest of the process is pretty straight forward, but unfortunately I didn't get any pictures. The threshold should now fit nicely under the trimmed door stop and the bottom of the threshold should be flush with the bottom of the frame. Before attaching the threshold, use some 100% silicone caulk on the edges of the threshold where it meets the frame and the door stop. **Be sure that you don't get caulk in the channel for the adjustable sill as this could cause the sill to become permanently fixed.

To attach the threshold back to the frame, it is recommended that long staples be used. Fortunately, I have a friend in the construction business who let me borrow his air stapler. If you don't have access to a stapler, I would recommend using a decking screw (something weather resistant) at least 2" long. You also want to pre-drill your screw holes to keep the bottom of the frame from splitting.

Once the frame is finished, reinstall the door into the frame, refit the hinge pins, and refit the shipping fasteners to keep the door from moving.

Step 5: Final Thoughts

The thought of cutting a brand new door was daunting at first. This process took me a couple evenings to complete. Each step took me a while as I contemplated the exact process that I wanted to do to avoid mistakes. Now that I've done one door, I'm confident I could do another within a few hours.

It's recommended to wait until after the door is completely installed before applying any finish to prevent marring, scratching or chipping the finish during installation. Since I'll need to modify my rough opening where this door is going, I haven't installed it yet. We've had 90+ degree days lately, so I'll wait until closer to fall for milder temps.

Thanks for reading. If I left anything out or if you have any questions, feel free to ask.