The Spatial Distribution Circuits use the Architectural Configuration Program to control the interior space allocation. Since a TARDIS's rooms and corridors are made from mathematical building blocks, its architecture can be remoulded. The operator can exert direct control of the interior architecture, designing things as he sees fit. The Protyon Unit's matter generation technology is used to generate custom designed modules (aka Storage Rooms) and upgrade modules which are then linked (via space-time bridges called Dimensional Junctures) to the Core Service Module. Using these Matter Control Projectors that surround the Core Service Module, the Dimensional Stabilizers can control any add-on modules.

Using Dimensional Junctures the rooms don't even have to be connected in any logical or mappable fashion. Multiple doorways can lead to the same room, and a single doorway can lead to two different places depending on which way you walk through it. Some frown on these sorts of configurations and believe that a properly stabilized Pedestrian Infrastructure should be able to be easily mapped in three dimensions. Temporal Locks are another way to customize the architecture. They can be used to separate part of the TARDIS interior, such as a Storage Room. Temporal Locks can even be used to connect that room to Normal Space via a Real World Interface. Once set up, a Temporal Lock is activated or deactivated by pressing the three green light-up buttons, found inside the room in question. Using this Architectural Configuration Program the operator can lock or unlock any door in a TARDIS interior from the console (there is a white flash around the frame when a door locks or unlocks). The interior can even be reconfigured to trap hostile entities in dead end corridors. It is even possible to vary the total interior volume of a TARDIS (see Dimensional Transcendence). It should be noted that complex modifications are very difficult, and the operator must have a Rassilon Imprimature or (at minimum) be telepathically linked with a TARDIS to ensure success.

A standard TARDIS has a million rooms and at least 12 levels. The total volume of rooms and corridors of a complete Type 40 TARDIS has been described as being about the size of a small town. It's also been described at being at least twice the size of San Francisco's Chinatown at the beginning of the 21st century. A fully guided tour of a Type 40 TARDIS could take a couple of years. Regardless of how the lifts and stairs are configured, a person will feel they are moving deeper the closer one gets to the Cloister Room.

Since the interior of a TARDIS is a Micro-Universe, if one sets off in one direction, one will eventually return to one's point of origin. For this reason a TARDIS could (like the N-Space Universe) be considered practically "infinite." This phenomenon is called infinite recursion.

The Protyon Unit keeps in constant communication with all parts of a TARDIS using Artron transmissions. The individual rooms of a TARDIS can be located using the spatial distribution circuits, which detect the unbalanced energy each room has with respect to the outside world. These rooms are monitored with the Architectural Configuration Indicators, ensuring that every part of a TARDIS is in constant communication with every other part. It should be noted that while Storage and Power Rooms are detectable, Zero Rooms are balanced to zero energy, and thus don't appear on the Architectural Configuration Indicators.

A TARDIS is constantly reforming, remodelling and redecorating various parts of its interior. In theory these redecorations are done in a manner that will be pleasing to the TARDIS's operator, but sometimes they are due to random dimensional feedback. Being four dimensional beings TARDISes are even able alter the architecture to accommodate new passengers before the ship's Time Lord knows there will be a new passenger. This can extend to rearranging and creating new living rooms. Minor alterations to the architecture can also occur when a TARDIS diverts Artron Energy to assist in a Time Lord's regeneration. A TARDIS with Time War era upgrades automatically reconfigures the architecture to make sure the room he needs comes to him. Over time a TARDIS grows, acquiring additional polychoral facets. When a TARDIS acquires extra internal dimensions its acronym changes from Time and Relative Dimension in Space to Time and Relative Dimensions in Space.

Despite these constant changes, the interior is always organized according to a specific geometry, which can be followed if you understand the pattern. The Time Sceptre is the central structure which contains the Interstitial Antenna, Control Rooms, Switch Room, Power Rooms, Dynamorphic Generators, Life Support, Basic Crew Facilities, Artron Mainframe, Transpower System, and the Cloister room. All other storage rooms are located in pods around the outer surface of the spherical micro-universe. Other things that remain fairly constant are the general floor plan (which does tend to vary slowly over time), and the color, which by default is off-white. Virtually all of the artronic, communications, and power linkages in a TARDIS pass through Dimensional Juncture to get wherever they need to be.

Using the Architectural Coordinate Selector, specific rooms can be deleted. Deleted rooms can either be jettisoned into the Space-Time Vortex or they can be converted into Artron Energy. This is done by collapsing their shells and feeding them into a TARDIS's Mass Converter. When calculating the energy release the operator is reminded that in the extra-temporal physics of the 5th dimension E = mc3. Since the mass of unused rooms can be converted into energy it is possible that a TARDIS creates the extra rooms to serve as an auxiliary power source. It would take the TARDIS less then a decade to regenerate several thousand tons of interior mass. The multidimensional mass of a complete TARDIS has been known to reach 68 thousand metric tons, but no upper limit has been discovered. It should be noted, that if the Architectural Configuration Program is used while a TARDIS is in the Vortex only the number of rooms to be moved/deleted can be specified but the actual choice of which rooms are moved/deleted is completely random.

If the Pedestrian Infrastructure in destabilized then the corridors and internal doors of a Timeship will be connected to different places depending on what angle you approach them. During the Time War the matter used for the internal structure of a TARDIS can withstand a full-on thermonuclear blast. It is theoretically impossible for there to ba a breach between the TARDIS's micro-universe and the Vortex. This is because the Internal Dimensional Units act to prevent internal trans-dimensional breaches. Nevertheless such breaches have been known to occur under extreme circumstances, and there is a high-pitched alarm designed to alert the crew if the structural integrity has been breached. Such a breach in the endo-shell of a TARDIS could (among other things) allow all the air to leak out.