The short answer
Use solid core on bedroom and bathroom doors and hollow core on closets. Lab-tested hollow core doors block noise at roughly STC 24 to 32; solid core doors reach about STC 32 to 36. Solid core costs more and weighs more, so spend it where tenants notice: the doors between people.
What’s inside each door
A hollow core door is two thin skins over a frame, filled with a honeycomb or similar lightweight core. A solid core door fills that space with particleboard, MDF or wood. Some suppliers also offer a middle option: a tubular particleboard core that’s lighter than full solid core but stiffer than honeycomb.
Side by side
| Hollow core | Solid core | |
|---|---|---|
| Core | Honeycomb or similar | Particleboard, MDF or wood |
| Sound (STC) | About 24 to 32 | About 32 to 36 |
| Feel | Light, can sound hollow when knocked | Heavy, closes with a solid feel |
| Dents and holes | Skins can dent or puncture | Much harder to damage |
| Weight on hinges | Light | Heavy; hinge screws should reach the framing |
| Cost | Lower | Higher |
| Best for | Closets, linen, utility | Bedrooms, bathrooms, dens |
Why the door matters more than the wall
A wall is only as quiet as its weakest part. Acoustic testing shows that when a door sits in a wall, the sound rating of the whole partition lands much closer to the door’s rating than to the wall’s. A well-built wall around a hollow core door performs like a hollow core door.
The gap under the door leaks sound too, so a solid core door with a large undercut gives back part of what you paid for. Keep undercuts to what the HVAC design needs.
A split that works for rentals
- Bedrooms and bathrooms: solid core. These separate people, and they take the most slamming.
- Dens and offices: solid core if someone will work from home there.
- Closets, linen and utility: hollow core. Nobody needs sound control in a closet.
On a typical two-bedroom with eight doors, that’s four solid and four hollow. We can quote the split per unit type, so the budget shows exactly where the money goes.
Sources
- Door flanking in demising walls: STC field test, Commercial Acoustics
- How door thickness affects sound ratings, Nick’s Building Supply
Code requirements change and local rules vary. Confirm sizes and clearances with your designer and building department before ordering. We supply doors and trim; we’re not a code consultant.
