Choosing a material for exterior mouldings is a long-term decision. The trim around windows, doors, rooflines and columns takes the full force of rain, sun and freeze-thaw cycles, and the wrong material means repainting, repairs or replacement within a few years. Here is how the common exterior moulding materials compare, including the ones we don't make.
The short version: Wood and MDF struggle outdoors, PVC and polyurethane move with temperature, and precast is durable but heavy. Cement-coated foam core composite gives a stone-like finish at a fraction of the weight, with a core that will not rot. Browse composite exterior mouldings.
Exterior Moulding Materials at a Glance
| Material | Weight | Rot and moisture | Movement | Upkeep |
|---|---|---|---|---|
| MDF | Moderate | Swells and breaks down when wet | High when wet | Not suitable outdoors |
| Wood | Moderate to heavy | Rots at joints and end grain | Seasonal swelling and shrinking | Regular repainting and repairs |
| PVC / cellular PVC | Light | Does not rot | Expands and contracts with heat | Low; seams can open |
| Polyurethane | Light | Does not rot | Moderate | Low; surface can chalk in sun |
| Precast concrete / GFRC | Very heavy | Durable, but can crack and absorb water | Low | Joint and sealant maintenance |
| Cement-coated foam core (Mouldex) | Light | Moisture-inert core, does not rot | Near-zero joint expansion | Prime and paint; no rot repairs |
MDF: Never Outdoors
MDF is made from refined wood fibres and resin. It is affordable and paints well indoors, but it absorbs water quickly and swells, so it should never be used outside or anywhere exposed to moisture.
Wood: Traditional, High Maintenance
Wood is the traditional choice for exterior trim and is easy to cut and shape on site. Outdoors, though, painted wood traps moisture at joints and end grain, which leads to cracking, splitting and rot. Horizontal pieces such as sills and bands fail first. Quality trim-grade lumber is also becoming more expensive.
PVC and Polyurethane: Rot-Free, but They Move
Cellular PVC and polyurethane mouldings do not rot, and they are light and easy to install. Their weakness is movement: plastics expand and contract with temperature, so seams on long runs can open, and dark colours in direct sun can make it worse. Many also read as plastic up close compared with stone or plaster.
Precast Concrete and GFRC: Durable, but Heavy
Precast concrete and GFRC give an authentic masonry look and are very durable. The trade-off is weight: large profiles need cranes or hoists, structural support and more labour, and long lead times are common because each profile needs a mould. Hairline cracks can also let water in during freeze-thaw cycles.
Cement-Coated Foam Core Composite: The Fifth Category
Mouldex exterior mouldings combine a precision CNC-cut EPS foam core with a hard, polymer-modified cementitious coating reinforced with fiberglass mesh. The result looks like carved stone or precast but weighs a fraction as much, so crews can install long lengths by hand without lifting equipment.
- Moisture-inert core: will not rot, swell or attract insects.
- Near-zero joint expansion: seams stay tight through seasonal temperature swings.
- Stone-like finish: crisp edges and a mineral surface that paints like masonry.
- Custom profiles: any profile can be adjusted, matched to existing trim or made from your drawing, including arches and circles.
- Works with any facade: stucco, EIFS, brick, stone veneer and more.
Like all mouldings, they are primed and painted after installation. Learn more about the fifth category of high-performance composite mouldings.
Which Material Is Right for Your Project?
- Replacing rotted wood trim: choose a material that will not rot, such as composite window trim and window sills.
- Stucco and EIFS facades: lightweight cement-coated composite blends with the wall finish; see our stucco mouldings.
- Large cornices and parapets: composite gives the look of precast without the weight; see exterior cornice mouldings.
- Porch columns: see composite column wraps.
Frequently Asked Questions
What is the best material for exterior moulding?
It depends on the project, but for most facades the best materials are ones that will not rot and do not move with temperature. Cement-coated foam core composite combines a stone-like finish with light weight and a moisture-inert core.
Can MDF moulding be used outside?
No. MDF absorbs water and swells, so it should only be used indoors in dry areas.
Is composite exterior moulding better than PVC?
Both resist rot. Cement-coated composite has near-zero joint expansion and a masonry-like finish, while PVC expands and contracts more with temperature and can look plastic up close.
Compare for yourself: order a free sample kit or talk to our team about your project.
