PBC Door Core Edge View
There is a variety of Door Cores that can be divided up into three main groups:

Solid Core 

This is the most common material for solid core doors.
It is the least expensive and is suitable for most interior flush doors.
Regular thicknesses of doors built from PBC are 1-3/4", 1-3/8", and 2-1/4"
For special low toxic applications and to meet some special requirements, doors can be manufactured using NAUF PBC (no added urea formaldehyde). 

           Particle Board Core (PBC) 

          Timberstrand Core (SCL) 

 Partical Board Door Core 
Timberstrand is the strongest of the cores and may be used for heavy duty applications and for doors with large cutouts for windows, panels, or louvers. Timberstrand is the heaviest of the cores.
Timberstrand is manufactured with water-proof glue so is suitable for doors in non-conditioned spaces. The glue is also NAUF so doors constructed with Timberstrand are eligible for NAUF requirements.
Regular thicknesses of doors built from Timberstrand are 1-3/4", 1-3/8", and 2-1/4" but we can accommodate almost any thickness.

          Stave (Lumber) Core 

There are three types of solid core we use predominantly:
Particle Board, Timberstrand, Stave (Lumber) 
Stave Cores are made from wood staves that are finger-jointed and glued together.
Stave Core doors are available with NAUF properties where the architect or local code specify materials that have no added urea formeldahyde.
Stave core is used where stronger, lighter cores are needed, and for doors that are more stable in non-conditioned spaces.
Door thickness are nominally 1-3/4" but other thicknesses may be available for low quantity orders.

Fire Core (45 min, 1 hr, and 1-1/2 hrs)

There are two types of fire core we use:

          Agrifiber Core (3/4 hr, 1 hr) 

Fire door construction using Lexington Agrifiber cores and components is our preferred choice. Agrifiber products are environmentally and user friendly, and make a robust fire door.  
Door thickness is a nominal 1-3/4".
Most 45 min. doors and single 60 min. doors can be made using Agrifiber construction methods. Fire doors are manufactured as neutral pressure (NP) or positive pressure (PP).  

         Mineral Core (3/4 hr, 1 hr, 1-1/2 hrs) 

Fire doors not using Agrifiber, with the exception of 20 min doors, are built using mineral core construction methods. 
Mineral fire doors consist of the mineral core itself with lengths of Firestop material used for stiles, rails, and blocking.
The available door thickness is a nominal 1-3/4".
Hollow core doors are usually purchased for two basic reasons: they weigh less, and are expected to cost less than solid core.  They are definitely lighter but this comes with the penalty of lower strength and lower stability.  A well built hollow core door manufactured with high grade honeycomb and solid wood stiles and rails is almost the same price as the basic solid core door.
A Hollow Core door is considered Inferior to a solid core door and will have a greater chance of telegraphing and warping.  It doesn't have the "quality feel" of a well made solid core door.
In many cases, because of weight restrictions, we supply hollow core doors.  However, we build them with solid wood stiles and rails, not with compressed cardboard or MDF.  For a typical 3/0 7/0 door or larger, the stiles and rails may be reinforced with Timberstrand and a center rail added.
The doors come with blocking for the lock unless there is a center internal rail,
Be warned, the office staff will try to talk you out of hollow core doors if at all possible!
There are two types of hollow core we use:

          Honeycomb Core

Polystyrene (Foam) Core is the cheaper of the two.
It has more temperature and noise insulating qualities, but is nowhere near as effective as solid core!
Small or Large Cell Honeycomb Core is the more robust of the two and is more expensive.  
It is the better choice if Hollow Core doors are a must..
More technical information can be found in the section "Cut Sheets".

      Foam Core

Timberstrand Door Core Slab
 Timberstrand Core Cutaway
 Stave Core Cutaway
 Agrifiber Core Edge View
 Agrifiber Door Core Slab
Mineral Core Edge View

20 min. fire labels are available with solid core doors.

Hollow Core