Internal panel doors

Panel doors  are panel and frame constructions; they're sometimes called rail and stile doors. The panel and frame construction is a traditional woodworking technique used to create a solid slab by joining separate pieces together. The panels themselves can be made from various materials, including glass. The most basic form consists of a single panel which is held in place with a frame made up of two vertical stiles and two horizontal rails. Panel doors are usually made with two or more panels, and modern panel doors have many different styles you can choose from. These extra panels are held with mid rails, mid stiles, and mullions, added to the basic frame. 

The panels themselves can be raised, with various profile designs, or flat. A flat panel has a face which lies flush with the grooves in the frame, so it's inset from the frame surface. Raised panels have their edges cut in profile, so their face is level with, or raised slightly above, the frame surface, producing a groove around the panel where it meets the frame pieces. Additional raised moulding trims can also be added to panel edges for a more decorative finish. 

Moulded doors are often used as an alternative to panel doors, as they can have their faces shaped to look like panel doors but are constructed in the same way as flush doors. If you choose a hollow-core moulded door they will be lighter than panels doors, which can reduce their risk of sagging. Panel doors are usually more expensive than flush doors, but that will depend on the quality. Higher quality flush doors can easily match the quality and price of many panel doors nowadays.

General variations of panel door design

While the panel door with six panels, three running down each side of the door, is traditional, and popular, there are a number of variations of this design and lots of different styles of panel doors available to choose from. Choosing the right style to suit your home can make a real difference to the overall look. 

Variations to the design of a panel door include different numbers of panels. Single panels or multiple panels can be used. The panels used can have straight edges or can be shaped with curves or other design features.

The way the panels are arranged varies with different designs. Panels can be in different configurations horizontally and vertically. There can be an even or odd number of panels and they can all be the same size as each other or different sizes. 

Some alternative designs include the cottage style panel door, with panels made from individual strips of material, or with carved grooves to emulate this. Also, some more unusual designs are available, such as doors with circular panels and diagonally set rails. These unusual designs are not commonly produced in panel constructions, as they're more difficult to produce and therefore, more expensive.

How is an internal panel door constructed?

Panel doors have panels which are held in grooves, or recesses, carved into the frames. The edges of the panels are purposely made a little thinner than the grooves they sit in so they 'float'. This allows natural expansion and contraction to occur without compromising the integrity of the door's structure, which occurs particularly in natural wood. This creates a door leaf which is less likely to warp than a solid slab.

The basic parts which make up a panel door are rails, stiles, and panels, and mullions if they're needed. The rails are the horizontal pieces used to frame the panels. All panel doors have a top and bottom rail. If there is more than one panel there will be further rails and mullions which separate them. 

The stiles of a panel door form the sides of its frame. They will usually be called the lock and hinge stiles, referencing which side of the door attaches to the frame by hinges and which has the handle or lock attached to it. Mullion is the name given to any other vertical frame pieces. These frame pieces join with mortise and tenon or dowelled joints, to produce a solid slab. 

When glazing panels are used in a panel door they will need to be held in by glazing bars, strips which secure glass into a frame, and can be separated with vertical frame pieces, sometimes called muntins. 

Decorative mouldings or trims are sometimes added around the edges of where the panels meet the frame pieces. These are raised strips, with shaped profiles, which add a decorative effect and enhance the look of the separate pieces. These can be used with glass panels as well as standard panels.

What can internal panel doors be made of?

Panel doors are traditional designs, but they are still popular today. The quality of the materials used to make the door will probably be reflected in the specifications and price of the door. Internal doors don't require the same properties as external doors and are usually made of cheaper materials.

Originally, panel doors would all have been made from natural solid wood, but that can be an expensive option today. Modern panel doors, like most other doors, are often made from a combination of different materials, with panels sometimes being made from different materials than the leaf's frame. Internal panel doors are usually made of engineered woods. These will sometimes be veneered with natural wood to enhance their appearance while keeping the price down. 

Natural wood  

The traditional material for making panel doors is solid natural wood. It's a long-lasting and visually attractive material. Natural woods can be painted or stained, and when used for internal doors they can also be varnished. Because natural woods can be expensive, they are also used as veneers on engineered woods. 

Softwoods and hardwoods can be used to make the parts of panel doors. The individual species of wood have different features, and this should be stated in the specifications of individual doors. High-quality woods will be expensive, but they usually have enhanced properties such as increased strength and durability, less chance of warping, or a particularly attractive appearance. 

Less expensive woods can be used for internal doors, as they don't have to face the same conditions as external doors. Natural woods can be prone to expansion and contraction with changes in temperature and humidity, and although this probably won't be significant for most internal doors, it's worth noting for doors in certain areas, such as bathrooms and kitchens.

Advantages and disadvantages of natural wood 

ADVANTAGES

DISADVANTAGES

• Ideal for veneers - looks attractive

• Can be painted, varnished, or

  stained

• Solid wood is easy to trim, sand, and refurbish

• Very durable and long-lasting

• It can be expensive

• It can be heavy

• Will need maintenance

Engineered wood

Engineered woods are man-made materials which use wood in their construction. For panel doors, plywood or some type of fibreboard can be used, often as a cheaper alternative to solid natural wood. They can have natural wood veneers attached to improve their appearance.

Plywood

Plywood is made of layers of thin sheets of wood fixed together with an adhesive to produce a solid panel. They are fixed together with each sheet having its grains running in a different direction to the sheet next to it. Various types of wood can be used to make plywood. The face sheets will often be a higher-quality wood than the core sheets. 

Plywood can be produced so that it is very strong, but it will be heavy. High-quality plywood can easily compete with some natural woods, and is less prone to warping, due to its cross-grain construction. This also means plywood can be expensive and will need to be maintained as much as natural wood. 

Advantages and disadvantages of plywood

ADVANTAGES

DISADVANTAGES

• Very strong throughout because each layer has its grain running in different directions

• Not as susceptible to water damage as fibreboards. It will soak up water, but much slower

• You can stain plywood

• Holds screws tightly when fitted through the face

• For its strength, it's relatively cheap compared to other materials

• Resistant to warping and shrinking with enhanced performance 

• Usually more expensive than most fibreboards

• The layers will be visible on the edges of boards unless they are finished properly

• Difficult to cut with a smooth edge - it often splinters

• The layers of low-grade plywood can peel away from each other

• The adhesives used in plywood need to be the correct type for the application, for instance being water resistant for bathroom doors

Fibreboard

Fibreboards are constructed differently to plywood, as they use wood fibre bonded together and pressed into a panel. For panel doors, medium-density fibreboard (MDF), high-density fibreboard (HDF), or hardboard is used. As the density level of fibreboards increases, they will get stronger and heavier, but they will also become more prone to warping.  

Fibreboards will need to be painted, as they can't be stained. They will not work well in exterior applications as they will absorb moisture if they get wet and this can permanently damage them. They will usually be the cheapest option compared to natural wood or plywood and are generally considered to be the least attractive.

Advantages and disadvantages of fibreboard 

ADVANTAGES

DISADVANTAGES

• Usually cheaper than plywood or natural wood

• Less tendency to expand or contract than natural wood

• Easy to paint, varnish, or attach a veneer or laminate to

• Doesn’t split easily

• Relatively strong

• More sustainable than natural wood

• Usually, has enhanced performance 

• Usually heavier than plywood or natural wood

• If not sealed properly on all sides it can soak up any moisture and can swell, causing permanent damage

• Will shrink in environments with low humidity

• Can't be stained

• Doesn't hold screws as well as plywood or solid wood. Fixing in screws can cause it to split

• It's not very attractive unless it has a quality finish applied

• Contains urea-formaldehyde which can be dangerous when sanding or cutting and small amounts will leak out over time unless they're finished correctly