Doors & Flush Doors · Specifications
Flush Door Thickness Guide
Flush door thickness isn't just about strength — it also has to match the door frame and hardware you're planning to use, so getting it right the first time saves a rework.
| Room | Recommended Thickness | Recommended Width |
|---|---|---|
| Bedroom | 30–32mm | 750–900mm |
| Bathroom | 30–32mm | 600–750mm |
| Entrance / Main door | 35–40mm | 900–1200mm |
Standard door height runs 1980–2100mm for interior doors, and 2100–2400mm for entrance doors.
What Else Thickness Affects
Solid vs Hollow Core
A solid-core door at a given thickness is considerably heavier and more rigid than a hollow-core door of the same measurement — thickness alone doesn't tell the whole story.
Matching the Frame Rebate
The door frame's rebate depth needs to match the door thickness precisely — an undersized or oversized door won't seat properly no matter how good the core is.
Grade by Room
MR grade for interior rooms, BWR or BWP for kitchens and bathrooms, and BWP for entrances — thickness and grade should be chosen together, not separately.
Measure Twice, Order Once
Always measure the existing frame opening before ordering a replacement door, since a mismatch in thickness or size means either a rework of the frame or an ill-fitting door. See our best plywood for doors guide for grade recommendations by room, and our flush doors for bathrooms guide for that specific application's sizing in more detail.
Frequently Asked Questions
What is the standard thickness of a flush door?
30 to 35mm is standard for most interior flush doors, with 32mm being a common minimum, while entrance doors often step up to 35–40mm.
Does door thickness affect soundproofing?
Yes — a thicker, solid-core door generally blocks more sound than a thin, hollow-core door, which matters for bedrooms or home offices where noise separation is a priority.
What thickness is best for a main entrance door?
35–40mm is typical for entrance doors, giving extra rigidity and security compared to the 30–32mm common for interior doors.
Can I change a door's thickness without changing the frame?
Not easily — the frame's rebate is cut to match a specific door thickness, so switching to a significantly different thickness usually means adjusting or replacing the frame as well.
Is a thicker flush door always better?
Not necessarily — thickness should match the application; an interior bedroom door doesn't need entrance-door thickness, and going thicker than needed adds cost and weight without a real benefit.
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