A front door is an assembly: slab skins and core, frame, sill, sweep, weatherstripping, glazing, hinges, lock preparation, flashing, and its connection to the wall. Comparing only fiberglass and steel skins misses the parts that control air, water, operation, and security. This page covers the complete replacement choice first, then the opening and exposure screen, the repair-or-replace decision, and surface damage.
Compare documented performance
ENERGY STAR says qualified doors must meet U-factor and, where applicable, solar heat gain coefficient requirements based on glazing level. DOE describes these ratings as properties of fenestration products and treats its guidance as technology-neutral. Compare the exact certified door configuration, including glass and sidelites, rather than assuming a skin material is warmer. The same door series can change ratings when glass, sidelites, or grids change, so verify the configuration rather than a brochure headline.
Record:
- full model and configuration;
- rough opening, jamb depth, swing, handing, sill height, and wall thickness;
- NFRC U-factor and SHGC where applicable;
- design-pressure, impact, or fire rating if the project requires it;
- glazing safety, privacy, and security details;
- frame, sill, weatherstrip, sweep, hinges, lock prep, and reinforcement;
- exposure limits, overhang requirements, finish schedule, and warranty exclusions;
- replacement parts and local authorized service.
Document the opening and exposure
A main entry adds weather, glass, hardware, accessibility, and appearance constraints to the basic material question. Measure and photograph the rough opening, jamb depth, sill, wall and exterior cladding, swing clearance, landing, step, overhang, prevailing weather, and drainage. Note the clear opening you need, threshold constraints, lock height, and any local accessibility or egress requirements. Check manufacturer color, exposure, and storm-door restrictions before choosing a dark finish in full sun.
Installation determines the result
DOE building-science guidance calls for properly lapped sill, side, and head flashing integrated with the wall drainage plane. It also says gaps at the rough opening must be air sealed with appropriate materials rather than fibrous insulation alone. A premium slab in an out-of-square, leaking, or poorly sealed opening remains a poor installation.
Get one quote that covers removal, concealed damage allowance, opening correction, sill pan and flashing, air sealing, trim, finish, hardware, permit where required, and disposal.
Repair or replace the existing door
Material should not decide repair versus replacement. Diagnose the failed part first.
| Symptom | Inspect before buying |
|---|---|
| Draft | Alignment, weatherstrip contact, sweep, sill, latch compression, and rough-opening air seal |
| Binding or uneven reveal | Hinges, fasteners, frame square, settlement, swelling, and sill support |
| Water at threshold | Exterior drainage, sill pan, flashing, seals, overhang, and door rating for exposure |
| Steel corrosion or dent | Finish breach, depth, edge involvement, core exposure, and manufacturer repair limits |
| Fiberglass crack or delamination | Extent, water entry, finish system, warranty, and manufacturer repair limits |
| Loose lock or hinge | Hardware, reinforcement, fastener anchorage, frame condition, and prior modifications |
DOE’s weatherstripping job aid says seals should prevent infiltration without impeding operation and that the door should be adjusted as required. Replacing seals without correcting alignment can make the door hard to latch and may not stop leakage.
A sound assembly may need only adjustment, compatible weatherstripping, a sweep, hardware, or finish work. A slab-only replacement requires a compatible frame, size, hinge and lock locations, sill, and weather seal. A prehung replacement is more appropriate when the frame, sill, flashing, alignment, or configuration must change. Water damage in the wall or subfloor expands the project beyond the door, so require a written scope for concealed damage and integration with the drainage plane.
Steel and fiberglass damage
Steel and fiberglass skins fail differently, but there is no universal easier or lower-maintenance category.
- Steel: distinguish a coating scratch, dent, edge deformation, corrosion, skin separation, or exposed core. Identify the approved cleaner, preparation, primer, topcoat, film thickness, and cure conditions. Do not trap active corrosion under filler or paint. Damage at an edge, hinge, or lock preparation affects fit and security differently from a cosmetic face dent.
- Fiberglass: distinguish coating wear from a crack, chip, delamination, edge damage, or core exposure. Textured wood-grain surfaces and factory stains can be difficult to blend. Use the manufacturer’s repair system rather than a generic automotive or marine patch.
A door that rubs, slams, leaks, or requires force may damage either skin, so check hinges, fasteners, frame square, latch alignment, sill, weatherstrip compression, sweep, and drainage before refinishing. Read the exact warranty and finishing instructions for initial finishing deadlines, approved colors and coatings, exposure or overhang rules, storm-door limitations, and glass cleaning, and keep labels and proof of purchase. Do not assign a repaint interval from skin material alone.
Related guides
Sources
Frequently asked questions
Which material costs less?
Compare complete configurations and installed scope. Glass, frame, finish, rating, size, hardware, opening repair, and labor can outweigh the skin material.
Should I replace the frame too?
Use a prehung system when the frame, sill, alignment, flashing, weatherstripping, or dimensions make a slab-only replacement unsuitable. A site inspection should decide. Slab-only replacement is not always cheaper: fitting, hinge and lock preparation, finishing, and correction of an old frame can exceed the apparent saving.
Does visible damage prove the slab is the leak source?
No. Water can enter at head or sill flashing, trim, wall drainage, glazing, or seals. Trace the path before ordering.
Can I use any exterior paint?
No. Use coatings and preparation allowed by the door manufacturer and compatible with the existing finish, substrate, color, exposure, and warranty.
Which skin resists dents better?
Impact response varies by skin gauge or laminate, core support, construction, and impact. Review exact product evidence and do not treat the material name as a test result.