Exterior doors come in three materials: steel, fiberglass and wood. The material matters less than the hole it has to fit. A standard American exterior door is 36 inches wide, 80 inches tall and 1 3/4 inches thick, and stock widths run 30 to 36 inches. If your opening is that, you have plenty of choice. If it is not, that one fact will shape the whole job.
What follows runs through steel, fiberglass and wood, then patio and storm doors. Most of it is about the three things a quote actually turns on: the size of your opening, which way the door has to swing, and whether you need a slab or a whole new frame. When I price an exterior door replacement, the frame is the first thing I look at, not the slab.
Start With the Opening, Not the Door
Almost everything a supplier asks you comes down to four numbers and one question. Take them before you fall in love with a door.
- Width of the door itself. Stock widths are 30, 32, 34 and 36 inches. Thirty six is the common one on a front entry and the one wide enough for a wheelchair. Older stock in places like Webster Groves and Kirkwood throws up openings that were never any of the four.
- Height. Eighty inches is standard. Ninety six inches, an 8 foot door, is a real option and a real upcharge.
- Thickness. Exterior doors are 1 3/4 inches. Interior doors are 1 3/8. If someone hung an interior door on your back wall at some point, that is why it never sealed.
- Jamb depth, meaning how thick the wall is. Measure from the inside face of the trim to the outside face. A 2×4 wall is usually 4 9/16 inches and a 2×6 wall is usually 6 9/16. Wider than either means the frame has to be built out.
Then the question, and it is the one people get wrong: which way does the door swing? Manufacturers do not all label this the same way, and I have seen two suppliers give opposite answers about the same door. So do not try to name it. Describe it: stand outside on the step, and say which side the hinges are on and whether the door comes toward you or goes away from you. Any supplier can work from that. A door ordered on the wrong hand cannot be flipped, and it is not a warranty claim, it is a reorder.
Write down whether there are sidelights or a transom too. A 36 inch door with a 12 inch sidelight on each side is a 60 inch opening, and that is a different order entirely. The rough opening a prehung unit needs is about 2 inches wider and 2 1/2 inches taller than the door itself.
Steel
A steel skin over an insulated core. It is the strongest of the three entry materials for the money and it holds its shape in a St. Louis July, when a wood door on a west wall is moving all day.
The number that separates a good steel door from a thin one is the gauge, and it reads backward: 20 gauge steel is thicker than 24 gauge. A dent in steel stays dented, so it is the wrong pick for a door a bike or a stroller goes past every day. We go into the gauges, the core and the honest downsides in the steel entry doors guide.
Fiberglass
A molded skin over the same kind of insulated core. It does not rot, it does not warp and it does not rust, which is why it has taken over the front of so many houses around here.
The wood grain versions are convincing at arm’s length and can be stained rather than painted. A scuff cleans up, but a deep gouge cannot be sanded out the way it can on wood, because the grain is molded into a thin skin rather than running all the way through. Our fiberglass entry door page shows the ranges we fit, and if you are down to these two, the steel versus fiberglass comparison is the one to read.
Wood
Nothing else looks like it, and a real wood door on the right house is worth what it costs. It is also the only one of the three that has a maintenance schedule.
What decides whether it survives here is not the door, it is the overhang above it. A wood door under a deep porch, facing north or east, can go five years or more between refinishes. The same door on a south or west wall with nothing over it takes sun and driving rain on the same face, and you will be refinishing it every year or two.
Patio Doors, Sliding and French
A sliding door gives you half its width as an opening and takes no floor space, so it suits a wall where furniture or a grill is already parked. A French pair is 2 doors in one frame, so it gives you the whole opening, but both leaves have to swing somewhere and that somewhere is usually the room.
Measure the swing before you decide. A 6 foot French door opening inward needs about 3 feet of clear floor on each leaf. If your dining table is there, the choice has already been made for you. There is more on the sliding side in the sliding patio doors post, and the hinged version on our French doors page.
Storm Doors
A second door in front of the first. Full view is glass top to bottom, half view is glass over a solid panel, and a retractable screen hides in the frame until you slide the glass down.
A full view storm door in front of a dark door on a sunny wall traps heat between the two. The air in that gap gets far hotter than the air outside, and door makers exclude that heat damage from their warranties. If your entry door is dark and faces south or west, either skip the storm door, pick a half view, or check the warranty wording before you order. The storm door post covers what they are genuinely good for.
Slab or Prehung
This choice moves your price more than the material does.
A slab is the door on its own. You keep the frame, the hinges and the threshold that are already there. It is cheaper and quicker. It only works if three things are true: the old frame is still square, the hinge mortises line up, and the bore for the handle and deadbolt sits at the same height. On a house built in the last twenty years those often line up. On an older St. Louis house they usually do not.
A prehung unit is the door already hung in a new frame, with a new threshold and new weatherstripping. It costs more and it is the one that actually fixes a draft, because the draft is almost never coming through the door. It is coming past a frame that has moved.
Two checks tell you which one you need. Close the door and look at the gap down the latch side. If it is wider at the top than the bottom, or the other way round, the frame is out of square and a slab will not fix it. Then slide a dollar bill into the closed door and pull. If it slides out easily anywhere around the perimeter, the seal has gone, and that is a frame conversation.
The One Number to Compare on Two Quotes
Every door sold in America is called energy efficient, so the phrase tells you nothing. The comparable figure is the U-factor, and it is printed on the NFRC label on the glass or on the spec sheet. It measures how fast heat escapes through the unit. Lower is better.
Ask both companies quoting you for the U-factor of the exact unit they are proposing, not the range the brand offers. Two doors that read the same on a brochure can be a long way apart once glass is in them, because glass is where most of the heat goes. A solid door and the same door with a full light are not the same product.
We fit ProVia units, and their dealer network lists us at Platinum level with a showroom. Their own locator will confirm that without taking our word for it.
Which Exterior Door Belongs on Your House
Pick the row that describes your situation rather than the material you like the look of. The material is the last decision, not the first.
| If this is true | Start here |
|---|---|
| Security is the first thing on your list | Steel |
| The door takes sun and rain with no overhang | Fiberglass |
| Kids, bikes and strollers go past it daily | Fiberglass |
| The house is period and the door is the point | Wood, under an overhang |
| You want the whole opening to open | French |
| There is furniture in front of the opening | Sliding |
| You want a screen and more daylight, on a pale door | Storm door over what you have |
| Your entry door is dark and faces south or west | Half view storm door, or none |
Every row above assumes the opening is standard. If your measurements came out odd, the size drives the decision and the material follows it, not the other way round.
When This Is Not Our Job
Four things people ask us for that we do not do.
- Garage doors. Different trade, different hardware, different people.
- Interior doors. We fit doors on the outside of the house.
- Repairing the door you have. If the frame is sound and square and the door just needs a new lockset or a hinge screw, you do not need a door company. We fit new units rather than rebuilding old ones.
- Commercial buildings. Everything we hang is engineered for houses, and that is where we stay.
The measurements tell you what is possible, not what a door will cost at your house. Nobody can give you that from a blog post. You can see finished work in our photo gallery.
Common Questions
Getting a Quote You Can Actually Compare
Take the four numbers, note which way the door swings, and decide whether you are buying a slab or a frame. With those in hand, two quotes become comparable instead of two prices with nothing behind them.
Still deciding how the door should look? Our front door ideas walk through glass, sidelites and finishes.
Our exterior door replacement page lists the ranges we carry, and there is a 10 year guarantee behind the workmanship. We will take the four numbers ourselves. Ask for a free in-home estimate or phone 314-277-5952, and the scope goes to you in writing before anything is ordered.
