Buying an Internal Door? Read the Core, Not Just the Catalogue Photo

Most of us start internal door shopping the same way: we see a lovely panel design, check the price, and maybe measure the opening. Construction comes later, if at all. That is understandable, but it is also how people end up with a door that sounds like a drum, dents when a laundry basket brushes past it, or refuses to sit flat after a winter of central heating. The core of a door matters more than the catalogue photo. Here is what you are really buying.

Hollow-core: lighter than it looks, and not always the villain

A hollow-core door is usually a timber frame with thin skins over a honeycomb or cardboard interior. That is why you can lift one with a single hand and why they are cheap. They are also easy to hang because they are light, which makes them tempting for cupboard doors, box rooms and spaces where the door is more of a screen than a security blanket.

The catch is everything else. Hollow doors are poor at blocking sound, they dent more readily, and they do not hold heavy hardware particularly well. A hollow door can be fine in a low-traffic wardrobe or a utility cupboard, but I would think twice about using one on a busy landing or outside a bathroom. They are also less forgiving of moisture, so a steamy room is not their natural home. They can be painted successfully, but thin skins show every lump and brush mark, so preparation needs to be better than you might expect.

Solid-core: the middle ground with a confusing name

Solid-core sounds reassuring, and it usually is, but it does not mean a door carved from one lump of oak. In most UK internal doors, solid-core means a timber frame filled with a denser core, often particleboard or a stabilised timber product, then faced with a veneer or a paintable skin. It is heavier than hollow-core, feels more substantial, and generally deals with noise and knocks better.

For bedrooms, living rooms and hallways, solid-core is often the sensible sweet spot. It holds hinges and handles more confidently, and it tends to feel less flimsy over time. It is not automatically fire-rated, though, and it is not automatically more stable than every engineered door. A solid-core door can still move if it is badly made or if the room swings between damp and desert-dry. Check the edge, the lipping and the manufacturer's trimming allowances before you commit.

Engineered doors: stability dressed as tradition

Engineered is one of those words that gets used like a compliment, but it describes a method rather than a guarantee. An engineered door is built from timber components arranged to reduce movement, often with a veneer on the outside. That can give you the look of oak, walnut or a painted period panel without the seasonal drama of a solid timber board.

Good engineered doors are stable, flat and pleasant to paint or seal. They can also be solid-core or closer to semi-solid, so do not assume the label tells you everything. The veneer needs a little respect: you cannot sand it like a slab of pine, and trimming is usually limited. Engineered doors tend to cost more than basic hollow or solid-core options, but they earn their keep in older homes where walls are rarely straight and doors need to stay put.

Fire-rated blanks: a different job entirely

A fire-rated door is not just a thick door with a serious expression. It is a tested door set, which means the door, frame, seals, hinges and hardware work together. A fire door blank sold on its own is only one part of that system. If it is going on a flat entrance, a garage link or another location covered by building regulations, the certification and the fitting matter as much as the slab itself.

This is where bargains get dangerous. An unlabelled door described as 'fire door style' is not a fire door. Drilling extra holes, trimming too much off the edges or swapping the hinges can all undermine a certified set. Fire doors are heavier, more expensive and less flexible, but they are doing a job that ordinary internal doors are not designed to do.

The showroom checks that tell you more than the label

Lift a corner if you can. Knock on the face. Look at the edge to see how the core is built and how generous the lipping is. Check the thickness: many standard internal doors are around 35 mm, while fire doors and heavier doors are commonly thicker. Ask what trimming is allowed, whether the door comes primed, and what the warranty actually covers.

Weight is a useful clue, but it is not proof of quality. A heavy door can still be poorly made, and a light door can be perfectly adequate for a cupboard. The more reliable questions are about core material, edge construction, moisture resistance and certification where relevant.

Room-by-room, construction earns its keep

For wardrobes and low-use cupboards, a hollow-core door can be a practical choice if the budget is tight. For bedrooms and living rooms, solid-core usually gives the best balance of price, quiet and durability. For bathrooms, look for moisture-resistant construction rather than a standard hollow skin. For hallways and busy family homes, a solid-core or engineered door will cope better with daily traffic. For flat entrances and other regulated locations, choose a certified fire door set and have it fitted properly.

Style still matters, of course. A door is a big visual element in a small British room, and the right panel design can do more for a hallway than a dozen cushions. But construction is what determines whether that door closes quietly, paints cleanly and still looks straight in five years. Start with the core, then choose the face.