On most new construction projects, the telecommunications rooms get a few square feet on the floor plan and little else. Architects, developers, and general contractors are, understandably, focused on structural, mechanical, and life-safety systems first — and the rooms that will eventually house a building's entire network often get sized, located, and powered as an afterthought. We see the consequences of that on a regular basis: undersized closets that can't fit the rack equipment a tenant needs, IDFs placed too far from the areas they're supposed to serve, and telecom rooms with no dedicated power or cooling. Every one of those problems is inexpensive to solve on paper during design and expensive to solve after drywall is up.
MDF and IDF, Briefly
The MDF (Main Distribution Frame) is a building's central telecom room — where internet service enters the building and where core network switches, servers, and cross-connects live. IDFs (Intermediate Distribution Frames) are the satellite rooms, usually one per floor or per wing, that extend the network out to nearby jacks, wireless access points, cameras, and phones. IDFs connect back to the MDF over a backbone cable run. Get the number, size, and placement of these rooms right during design, and the building's network is straightforward to install and easy to maintain for its entire life. Get it wrong, and every tenant improvement, equipment refresh, or added device becomes a fight against space and distance constraints that should have been solved on the drawings.
Sizing the Room Correctly the First Time
TIA-569-D, the industry standard for telecommunications pathways and spaces, calls for a preferable telecommunications room of at least 100 square feet with a 10-foot by 10-foot footprint, and no side smaller than 8 feet. That's a preference, not a hard minimum, but rooms that come in well under it routinely can't accommodate the racks, patch panels, cable management, and clearance an active network requires — let alone room to grow. A telecom room is one of the few spaces in a building where "we'll make it work" during construction usually means a retrofit within a few years.
MDF-to-IDF Connectivity: Distance Drives the Design
The number and placement of IDFs in a building isn't a design preference — it's dictated by cable distance limits. TIA-568 caps copper horizontal cabling at a 90-meter (295-foot) permanent link, with a 100-meter (328-foot) maximum once patch cords are factored into the full channel. That's the maximum distance from an IDF to the farthest device it serves. On a large floor plate, that limit alone can require more than one IDF per floor, which needs to be planned for before the electrical and mechanical layouts are locked.
For the backbone connecting each IDF back to the MDF, fiber has become the standard rather than the exception. It isn't subject to the same 100-meter copper ceiling, handles far more bandwidth, and isn't affected by electrical interference from nearby equipment. OM4 multimode fiber, for example, supports 40 Gbps at 150 meters and 100 Gbps at 100 meters — comfortably covering most MDF-to-IDF runs in a multi-story building. The design we recommend on almost every project is a hybrid one: fiber for the MDF-to-IDF backbone, copper for the horizontal runs out to the powered edge.
Power, HVAC, and Grounding
Telecom rooms need dedicated infrastructure, not whatever's left over. Standard guidance calls for two dedicated, non-switched 120V/20A duplex outlets spaced roughly every 6 feet around the perimeter wall, mounted about 6 inches above the floor. Cooling matters just as much: active network equipment generates real heat, and TIA-569 guidance calls for telecom rooms to be held to the same temperature as adjacent office space, harmonized with ASHRAE standards — not left to drift with an unconditioned mechanical space. Grounding and bonding also need to be designed in from the start under TIA-607: each telecom room needs a grounding busbar bonded to the building's bonding backbone, and any cable trays in the room need to be bonded as well.
Conduit, Pathways, and Coordinating With the GC Early
Pathway sizing is easy to underestimate. Conduit runs between telecom rooms should be a minimum of 1 inch in diameter, shouldn't exceed 100 feet without a pull box, and should be sized using roughly a 50% fill ratio so cable can actually be pulled without damage. Any conduit or cable tray passing through a fire or smoke barrier needs to be fire-stopped. None of this can be solved after the fact without opening walls — it has to be coordinated with the general contractor and MEP trades while pathways are still being routed, so cable trays don't end up fighting HVAC ducts, plumbing, or structural members for the same ceiling space.
Why This Is Worth Solving at the Design Table
Every item above is inexpensive to get right on a drawing set and expensive to fix in a finished building. That's the pattern we run into most often on new construction: a telecom room that was sized, located, or powered without input from anyone who has to actually rack and run a network in it. Bringing a technology integrator into the conversation during design development — alongside the architect and MEP engineer, not after their drawings are finished — is the difference between a network that's straightforward to install and one that requires change orders once the space is already built. That's the role we play on projects across Austin, San Antonio, Dallas, and Houston: reviewing telecom room placement and sizing, planning MDF-to-IDF backbone routing, and making sure power, cooling, and pathways are specified correctly before construction starts.
Frequently Asked Questions
What's the difference between an MDF and an IDF?
The MDF (Main Distribution Frame) is the central telecom room where a building's internet and voice services enter and where the core network equipment lives. IDFs (Intermediate Distribution Frames) are secondary telecom rooms, typically one per floor or per wing, that extend the network out to nearby end devices. IDFs connect back to the MDF over a backbone cable run, and each IDF then serves the horizontal cabling to jacks, access points, cameras, and phones in its area.
How big should a telecom room be in new construction?
Per TIA-569-D, a preferable telecommunications room is at least 100 square feet with a 10-foot by 10-foot footprint, and no side should be smaller than 8 feet. Rooms sized smaller than this on the initial floor plan are one of the most common problems we see once equipment, patch panels, and rack clearance requirements are added later.
How far can an IDF be from the devices it serves?
TIA-568 limits copper horizontal cabling to a 90-meter (295-foot) permanent link, with a 100-meter (328-foot) maximum for the full channel once patch cords are included. That distance limit, measured from the IDF to the farthest jack, camera, or access point it serves, is what determines how many IDFs a building needs and where they need to be located — not an afterthought decision made once walls are already framed.
Should MDF-to-IDF backbone cabling be copper or fiber?
Fiber is now the standard choice for backbone runs between the MDF and IDFs. It isn't bound by the 100-meter copper limit, supports far higher bandwidth, and is immune to electrical interference. OM4 multimode fiber, for example, supports 40 Gbps at 150 meters and 100 Gbps at 100 meters. The typical modern design uses fiber for the MDF-to-IDF backbone and copper for the horizontal runs out to the edge devices.
When should a technology integrator get involved in a new construction project?
As early as the design development phase, before conduit pathways, electrical panels, and room layouts are finalized. Telecom rooms that get value-engineered down in size, placed without dedicated power and HVAC, or positioned without regard to cable distance limits are expensive and disruptive to fix once walls are framed. Bringing in a low-voltage and network integrator alongside the architect and MEP engineer avoids that rework.