You’ve got this beautiful, sprawling home—maybe 4,000 square feet, maybe 8,000. And suddenly you’re staring at a security panel wondering how many motion sensors you actually need and where the hell they should go.
Here’s what most security companies won’t tell you upfront:
Large homes are deceptively hard to secure. It’s not just about buying more sensors. A 5,000-square-foot home isn’t just a 2,000-square-foot home with extra rooms tacked on.
You’ve got longer hallways, multiple staircases, guest wings that feel like separate apartments, and enough entry points to make your head spin.
I’ve walked through hundreds of large homes doing security assessments, and I see the same mistakes over and over. Homeowners either go overboard and install 30 sensors (most of them useless), or they cheap out and leave gaping holes in coverage. Neither approach works.
So let’s talk about where to install motion sensors in large homes the smart way—strategically, efficiently, and without blowing your entire security budget on equipment you don’t need.
Why It Is Important To know Where to Install Motion Sensors in Large Homes
Before we dive into specific rooms, you need to understand how these things actually work. Most residential motion sensors use PIR (Passive Infrared) technology, which detects body heat moving across the sensor’s field of view.
Here’s what matters for placement:
- Detection range: Most quality sensors cover 30-40 feet. Some manufacturers claim 50, but in real-world conditions with furniture and room layouts? Stick with 30-35 feet of reliable coverage.
- Coverage angle: You’re typically looking at 90-110 degrees of horizontal coverage. Think of it like a cone spreading out from the sensor.
- Height matters: Mount these at 6-8 feet for optimal performance. Too high and you lose sensitivity to floor-level movement. Too low and large dogs will trigger them constantly.
Now here’s where large homes get tricky. In a compact house, one sensor in a central hallway might cover three doorways.
In a large home? That same hallway might be 60 feet long with five bedrooms branching off. You’re going to need multiple sensors, and you need to think about coverage zones, not just room counts.
Also, if you’ve got vaulted ceilings in your foyer or great room (and let’s be honest, you probably do), standard mounting heights don’t work. A 20-foot ceiling changes everything about sensor angles and coverage patterns.
One more thing: pet-immune sensors are not optional if you have dogs over 40 pounds. I can’t tell you how many homeowners I’ve worked with who were dealing with false alarms three times a week because their golden retriever kept setting off standard sensors. Save yourself the headache.
Where to Install Motion Sensors at Main Entry Points in Large Homes
This is where you start. Every. Single. Time.
Entry points are where 90% of break-ins happen, and in a large home, you’ve got more of them than you think.
1. Front Door and Foyer Motion Sensor Placement
Your front entrance needs coverage, period. Mount a sensor on the wall adjacent to your door at about 7-8 feet, angled to catch anyone who walks into the foyer.
Here’s a mistake I see constantly: people mount sensors directly above the door. Don’t do this. You create a blind spot immediately below the sensor. Mount it on the side wall instead, facing across the entryway.
If you’ve got one of those grand two-story foyers (and I’m betting you do), you might need a sensor on both the main level and at the top of the stairs. Heat rises, and sometimes a sensor mounted at 8 feet in a 24-foot foyer doesn’t give you the coverage you think it does.
2. Garage Entry Door Motion Detector Positioning
This is the entry point most people forget, and it’s the second most common place burglars actually enter. Why? Because your garage door to the house is usually less secure than your front door, and garages offer cover while someone’s working on getting inside.
You want a sensor positioned to cover both the door from garage to house AND movement within the garage itself. If you’ve got a three-car garage, consider two sensors—one at each end—because 30 feet of width plus vehicles blocking line-of-sight means dead zones.
3. At The Back and Side Doors
Kitchen doors, mudroom entrances, that side door you use to take out the trash—these need dedicated coverage. Burglars love these entry points because they’re less visible from the street.
Pro tip: Don’t mount directly above these doors either. Put the sensor on an adjacent wall, about 10-12 feet from the door, angled to catch approach. This way you’re detecting movement before someone’s already inside.
4. Basement or Cellar Entrance Motion Sensor Installation
External basement access is often the weakest link in large home security. Bulkhead doors, ground-level walk-ins, window wells big enough to crawl through—these are entry points that are out of sight and out of mind for most homeowners.
If you have exterior basement access, you need a sensor covering that door from inside. If your basement has interior stairwell access from the main floor, you need coverage there too.
We’ll talk more about stairwells in a minute, but this is critical: basements often house expensive equipment, workshop tools, and in newer large homes, entire rec room setups worth tens of thousands.
Bottom line on entry points: I typically recommend 5-8 motion sensors just for doors in a large home. Yes, that sounds like a lot. It’s not. It’s the foundation of everything else.
Best Places to Install Motion Sensors in Hallways and Corridors
Okay, here’s where strategic thinking separates smart installations from wasteful ones.
Hallways are chokepoints. Think about it: an intruder can’t get from your living room to your bedroom wing without passing through hallways. They’re natural detection tunnels, and in large homes, they’re long enough that you need to plan carefully.
The key principle: Mount sensors at one end of the hallway facing down the corridor, not in the middle.
Why? Because sensors detect movement across their field of view, not directly toward them. A sensor at the end of a 40-foot hallway, mounted at 7 feet and angled slightly downward, will catch anyone moving through that entire corridor.
If your hallway exceeds 40 feet (and in large homes, some do), you need sensors at both ends facing toward the middle. I know that sounds redundant, but it’s not. You’re eliminating blind spots.
For L-shaped or T-junction hallways—common in homes with multiple wings—mount your sensor at the corner, positioned to cover both directions. A single well-placed sensor at a junction point can cover three different approach angles.
Here’s what doesn’t work: putting a sensor mid-hallway. You create dead zones at both ends, and you’ve wasted a sensor that could have been covering a different area entirely.
One more thing about hallway placement in large homes: you often have main hallways and secondary service corridors (especially in older estate homes or new construction with separate staff/utility areas). Don’t forget those secondary corridors. They’re how someone moves through your home without being seen from main living areas.
Motion Sensor Placement for Stairwells in Multi-Story Large Homes
If hallways are chokepoints, staircases are gatekeepers. Control the stairs, control access between floors.
Most large homes have at least one main staircase, and many have two or three if you count basement stairs and back staircases. Each one needs coverage.
1. Main Staircase Motion Sensor Installation
You need sensors at both the top and bottom of your main stairs. Not either-or. Both.
At the top: Mount the sensor on the second-floor landing wall, facing down the stairwell. This detects anyone coming up before they reach the bedroom level.
At the bottom: Position your sensor to cover the base of the stairs and the approach from the main floor.
For grand staircases—the kind with 20+ steps and a landing halfway up—add a third sensor at the mid-landing if your main floor to second floor vertical distance exceeds 15-16 feet. PIR sensors can lose sensitivity over long vertical distances.
2. Place Motion Sensors on Secondary Staircases
Back staircases, servant stairs in older homes, that narrow stairway from the kitchen to the second floor—these are often forgotten, and they shouldn’t be.
Burglars who’ve done homework on large homes specifically look for these secondary access routes. They’re quieter, more private, and often less monitored.
A sensor at the top of a back staircase is usually sufficient unless the stairwell is unusually long or has multiple landings.
3. Basement Stairs Motion Detector Positioning
Basement stairs are critical, especially in finished basements with expensive equipment or in homes where the basement has its own exterior access.
Mount your sensor at the top of the basement stairs, facing down. This catches anyone coming up from below and gives you early warning before they reach your main living level.
In a three-story home, you’re looking at 4-6 sensors just for stairwell coverage. That’s on top of your entry point sensors. Starting to see why large homes need 15-20+ sensors for proper coverage?
Installing Motion Sensors in Master Bedroom Suites and Private Areas
Now we’re getting into the inner sanctum. This is where you sleep, where your kids sleep, where valuables are stored in closets and safes.
The Philosophy check: You want to detect intruders before they reach bedroom doors, not after they’re already in your private spaces.
1. Bedroom Wing Coverage
If your master suite is part of a dedicated bedroom wing (common in modern large home layouts), you need a sensor in the hallway approach before the wing itself. This is your early warning system.
Mount it where the main house hallway transitions into the bedroom corridor. Someone moving from the main staircase toward bedrooms has to pass this sensor first.
2. Walk-In Closets and Dressing Rooms
Here’s where opinions differ among security professionals, and I’ll give you mine: if your walk-in closet is over 150 square feet and houses jewelry, watches, a safe, or other high-value items, it deserves its own sensor.
Why? Because in large homes, master closets are often rooms unto themselves—sometimes with exterior windows, sometimes with doors to other areas. A determined thief who’s made it past your other sensors might spend 10 minutes working on a safe. You want to know they’re in there.
For guest bedroom closets? Skip it. Not worth the sensor or the monitoring.
3. Guest Suites
If you have a guest suite that’s essentially a separate apartment with its own exterior access (and in homes over 6,000 square feet, this is increasingly common), treat it like a mini-home within your home. Entry door coverage, hallway coverage if applicable.
If it’s just extra bedrooms down the hall? The hallway sensor we already discussed covers the approach to these rooms adequately.
The master bedroom strategy comes down to this: one sensor for hallway approach to the entire bedroom wing, plus one sensor inside any closet or dressing room over 150 square feet with high-value storage. Most large homes need 2-3 sensors for the bedroom area.
Where to Place Motion Detectors in High-Value Rooms
Let’s talk about the rooms where you keep the expensive stuff.
1. Home Office and Study Motion Sensor Installation
If your home office contains computers, important documents, business equipment, or anything you’d be devastated to lose, dedicated coverage is worth it.
Position your sensor to cover the entry door and have line-of-sight to the desk area. One sensor in a typical 200-square-foot home office is sufficient.
I worked with a client last year who ran a consulting business from home. His office had three computers and years of client files. We put a sensor directly covering his office door approach.
Three months later, his system triggered at 2 AM. Police arrived to find someone had gotten through a side entrance and was making a beeline for the office (probably watching the home and knew it was a business). That single sensor paid for the entire security system.
2. Media Rooms and Home Theaters
Home theaters in large homes often represent $50,000-$150,000 in audio-visual equipment. That’s an attractive target.
One sensor positioned at the entry is usually enough unless your theater exceeds 500-600 square feet. Position it to cover both the doorway and the equipment wall.
3. In Wine Cellars and Specialty Rooms
Wine cellars, gun rooms, safe rooms, workshops with expensive tools—these specialized spaces in large homes need individual attention.
Wine cellars are interesting because they’re often in basements, climate-controlled, and contain collections worth five or six figures. You want motion detection here for two reasons: asset protection and access control (since these rooms are often in less-monitored basement areas).
4. Gun Rooms and Safe Room Motion Detector Positioning
If you store firearms in a dedicated room (required in some jurisdictions for collections over certain sizes), motion sensor coverage isn’t optional—it’s a legal and safety imperative.
For gun rooms and safe rooms, consider dual-technology sensors that use both PIR and microwave detection. They’re more expensive but virtually eliminate false alarms while providing higher security.
High-value rooms are straightforward: one sensor per specialized space where you keep expensive or sensitive items. For most large homes, that’s 3-5 additional sensors beyond what we’ve already discussed.
Additional Motion Sensor Installation Locations for Large Homes
We’ve covered the essentials. Now let’s talk about the maybes—areas where sensor installation depends on your specific home layout and risk factors.
1. Living Rooms and Great Rooms
In most cases, living rooms and great rooms don’t need dedicated motion sensors if they’re centrally located and surrounded by areas that are already covered.
The exception: if your great room has direct access to exterior doors (like French doors to a patio), you need coverage. Also, in homes where the great room is 800+ square feet with valuable art or furnishings, consider a corner-mounted sensor that covers the space and the access points.
2. Kitchens and Dining Areas
Kitchens are medium priority. They often have back door access (which you’ve already covered with entry point sensors), but the kitchen interior itself? Usually not necessary unless it’s a massive chef’s kitchen in a separated wing.
Formal dining rooms rarely need dedicated sensors unless they contain valuable china or silver that’s stored in built-ins.
3. Finished Basements and Recreation Areas
If your basement is finished living space with home theaters, game rooms, or gym equipment, you need more than just stairwell coverage.
The decision point: does your basement have exterior access? If yes, treat it like a ground floor with entry point coverage, hallway coverage if applicable, and coverage for high-value rooms.
If your basement is only accessible from interior stairs and you’ve got the stairwell covered, you can often skip additional basement sensors unless specific rooms down there contain valuable equipment.
4. Attached Garages Interior Coverage
We talked about garage entry doors earlier, but what about the garage interior itself?
For standard 2-car garages, one sensor covering the door to the house plus the interior space is usually sufficient. For 3+ car garages, especially those with workshop areas or expensive vehicle collections, consider two sensors—one at each end—to eliminate blind spots created by vehicles.
5. Attic and Utility Spaces
Unless your attic is finished living space or has exterior access (gable vents large enough to crawl through, exterior attic doors), skip sensors here. It’s low probability, and you’re better off spending that sensor somewhere else.
Utility rooms, laundry rooms, mechanical spaces? Also low priority unless they contain expensive equipment or have exterior access.
Common Motion Sensor Installation Mistakes in Large Homes
Let me save you from the mistakes I see every week.
Mistake #1: Relying Too Heavily On Outdoor Sensors
Outdoor motion sensors are great for perimeter detection, but they get false alarms from animals, weather, and moving vehicles. They complement indoor sensors; they don’t replace them. Your indoor sensor network is your primary defense.
Mistake #2: Ignoring Pet-Immune Settings
If you have dogs over 40 pounds and you’re using standard PIR sensors, you’re going to get false alarms. Spend the extra $15 per sensor for pet-immune models. Your sanity is worth it.
Mistake #3: Mounting Sensors At Wrong Angles
Too high and you lose floor-level detection. Too low and you create blind spots above. The 7-8 foot sweet spot exists for a reason. Also, angle slightly downward (about 10-15 degrees from horizontal) for optimal coverage.
Mistake #4: Forgetting About Guest Wings
That detached or semi-detached casita you use for visitors? It needs its own security coverage. Don’t assume your main house sensors cover it—they don’t.
Mistake #5: Not Testing After Installation
This is huge. After you install sensors, actually walk through every entry point and pathway while armed. Have someone monitor the system to verify every sensor is detecting movement where it should. I can’t tell you how many installations I’ve fixed where sensors were mounted but never tested, leaving dead zones no one knew about for months.
Mistake #6: Putting Sensors In Direct Sunlight Or Near Heat Sources
PIR sensors detect infrared radiation (heat). Direct afternoon sun through a window or placement near heating vents can cause false triggers. Think about sun angles and HVAC placement when mounting.
Motion sensors are fantastic at detecting movement, but they’re really just one piece of a much bigger puzzle. Think of them as your home’s nervous system, but what good are nerves without eyes?
That’s why I always tell people to think about adding security cameras for maximum coverage once their sensors are dialed in. You want to actually see what triggered that 2 AM alert, not just know that something moved near your garage.
And honestly? Prevention beats detection every single time. I’ve seen too many people dump thousands into monitoring systems while leaving their homes basically screaming “easy target” to anyone walking by.
Positioning security lighting with motion sensors for deterrence is ridiculously effective—burglars are lazy, and they’ll skip a well-lit house for the dark one next door almost every time. It’s the security measure that works before anyone even thinks about breaking in.
But let’s back up for a second. Before you go all-in on sensors and cameras, you might want to check if you’re leaving the front door wide open, metaphorically speaking.
I also wrote a whole piece on the most common home security vulnerabilities because I kept seeing people install $500 smart sensors while their sliding glass door could be popped open with a screwdriver. Fix the basics first, then layer on the tech.
How Many Motion Sensors Does a Large Home Actually Need?
Okay, let’s get practical. You want numbers.
Here’s my general formula based on 20+ years in security:
3,000-5,000 sq ft homes: 10-14 sensors 5,000-7,500 sq ft homes: 14-20 sensors
7,500-10,000 sq ft homes: 20-28 sensors Over 10,000 sq ft: 28-35+ sensors
These numbers assume standard layouts with normal entry point counts, 2-3 stories, and typical high-value room distribution.
What increases your sensor count:
- Every additional floor (finished basements, third floors)
- Detached structures that need coverage (guest houses, pool houses)
- Complex layouts with many wings and long corridors
- Multiple high-value asset rooms requiring dedicated coverage
- Large garages (3+ cars) needing multi-sensor coverage
What keeps your count lower:
- Open-concept floor plans where one sensor covers multiple sight lines
- Single-story layouts (though large single-story homes are rare)
- Centralized room arrangements without long corridors
- Smart placement at chokepoints rather than room-by-room coverage
Here’s the truth: I’d rather see 15 perfectly placed sensors than 30 randomly positioned ones. Quality placement beats quantity every time.
The sweet spot for most large homes in the 5,000-7,000 square foot range is 16-22 sensors. That gives you comprehensive coverage without redundancy.
Budget-wise, you’re looking at $30-75 per sensor for quality PIR units, plus installation if you’re not doing it yourself. Figure $800-1,800 for sensors alone in a properly equipped large home system.