Short answer
Use primed MDF for painted trim in dry rooms: it is the cheapest and smoothest. Use primed finger-joint pine where it might get damp or knocked, because it handles moisture and holds nails better. Use solid wood if you want to stain. Use PVC outdoors and in very wet spots. Polystyrene casing is prefinished and sold as moisture resistant (maker claim).
The materials compared
Material costs from Fixr (composite, hardwood and PVC rows); other notes from makers
| Material | Paint / stain | Moisture | Strength | Interior cost per ft |
|---|---|---|---|---|
| Primed MDF | Paint only | Poor: swells if wet | Hard face, brittle edges | $0.60 to $4 |
| Finger-joint pine | Paint (sold primed) | Fair: recovers when dry | Holds nails well | Not listed |
| Solid wood | Paint or stain | Fair, if sealed | Good; hardwoods dent less | $0.75 to $6 |
| PVC | Paint optional | Excellent: rot free | Tough, flexes | $0.75 to $7.40 |
| Polystyrene | Prefinished | Sold as moisture resistant | Light; dents | Not listed |
Costs are materials only, per linear foot, from Fixr (updated January 2025). Moisture and strength notes come from Intrim and Fine Homebuilding.
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01Lowest cost
Primed MDF casing
Best for: painted trim in bedrooms, living rooms and hallways
- Finish
- Factory primed
- Stain
- No
- Wet rooms
- Avoid
- Smooth face takes paint well
- Edges are brittle when nailed close to an end (Intrim)
- Cutting makes fine dust: wear a respirator
-
02All-rounder
Primed finger-joint pine
Best for: painted trim anywhere indoors, including baths and laundry
- Finish
- Factory primed
- Stain
- No (joints show)
- Wet rooms
- OK if painted
- Short clear pieces joined end to end, so it stays straight
- Holds nails and screws well and is lighter than MDF (Intrim)
- Costs a little more than MDF
-
03Stain grade
Solid wood casing (oak, pine, poplar)
Best for: stained trim and period homes
- Finish
- Unfinished
- Stain
- Yes
- Wet rooms
- Seal all faces
- The only choice for a stained look
- Hardwoods like oak resist dents better than pine
- Seal the back and cut ends to limit movement
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04Wet areas
PVC casing
Best for: exterior doors, basements and very wet rooms
- Finish
- White
- Stain
- No
- Wet rooms
- Yes
- Westlake Royal says its cellular PVC will not rot and absorbs virtually no water (maker claim)
- Use PVC adhesive on miter joints
- Dark paint needs a vinyl-safe formula
-
05Prefinished
Polystyrene casing
Best for: quick, no-paint trim in damp rooms
- Finish
- Prefinished
- Example
- 11/16 x 2-3/8 in x 7 ft
- Wet rooms
- Maker says yes
- Inteplast says its colonial casing is moisture resistant and fine for basements, bathrooms and kitchens (maker claim)
- Comes prefinished in white and wood looks
- Lighter and softer than wood
Room by room
- Bedrooms, living rooms, halls: primed MDF or finger-joint pine.
- Bathrooms, laundry, mudrooms: finger-joint pine, PVC or polystyrene. Keep MDF away from floors that get mopped (Intrim).
- Stained trim: solid wood only.
- Exterior doors: PVC or primed wood brick mold.
Costs for a whole job are in door trim cost.
Questions people ask
Is MDF trim OK in a bathroom?
It is a risk. Intrim, a molding maker, says MDF should never go in wet areas or where floors are mopped or steamed, because it can absorb moisture and swell. Primed finger-joint pine or PVC are safer in bathrooms.
Can you stain finger-joint pine?
Not well. The joints between the short pieces show through stain, which is why finger-joint pine is sold primed for paint. Use solid wood for stained trim.
What is the cheapest door trim?
Primed MDF is usually the lowest cost paint-grade casing. Fixr lists composite (MDF) interior trim from about $0.60 to $4 per linear foot.
Does PVC trim need painting?
No, it comes white and does not need paint to survive, but it can be painted. Westlake Royal says its PVC brick mould can be painted with 100 percent acrylic latex, and to use a vinyl-safe paint for dark colors.
Sources
Last reviewed October 12, 2026. Profiles, sizes and listings change; check the product details before you buy, and follow the maker’s instructions.