No-Screw Cat Window Perches: A Renter Safety Test

What makes a cat window perch truly renter-friendly?

Worried that “no screws” may still leave marks, residue, or a damaged window?
This section defines renter-friendly installation through reversibility, mount stability, surface protection, and useful indoor enrichment.

A truly renter-friendly cat window perch can be removed without holes, adhesive residue, cracked glass, compressed trim, or other visible damage. It must also remain stable under the way your cat actually uses it—not merely under a gentle static load.

We use a practical metric called the Lease-Safe Enrichment Score. It weighs four factors:

• Reversibility: Can every component be removed without tools or permanent alteration?
• Surface risk: Could the mount stain, scratch, compress, peel, or crack the supporting surface?
• Mount stability: Does the support resist downward weight, sideways movement, and jumping?
• Deposit exposure: Could installation create damage that a landlord may classify as more than normal wear?

This matters because “no-screw,” “no-drill,” “removable,” and “damage-free” are not interchangeable claims.

What do no-screw, no-drill, removable, and damage-free mean?

• No-screw: The product does not use screws, but it might use adhesive, pressure, clamps, or suction.
• No-drill: No holes are drilled, though pressure marks or adhesive residue may still occur.
• Removable: The perch can be taken down, but removal may leave discoloration, residue, or dents.
• Damage-free: This is a broad marketing claim unless the manufacturer defines compatible surfaces, installation limits, and removal instructions.

A suction cup cat window perch may be highly reversible on smooth, intact glass. The same perch may be unsuitable for textured glass, a film-covered pane, or glass with a small edge crack.

A sill clamp mount avoids suction dependence, yet an overtightened clamp can crush soft wood, mark painted trim, or interfere with the window sash. “No hardware” does not mean “no load.”

Why does rental damage deserve its own buying criterion?

Security-deposit rules differ by state, lease, and type of housing. A useful official example comes from the California Department of Justice’s security-deposit guidance, which distinguishes ordinary wear from damage that may support deductions.

A perch-related hole, peeled finish, broken blind, or cracked pane could become a repair issue rather than ordinary wear. That possibility makes documentation and reversible installation financially relevant.

Before installing, check:

• Lease restrictions: Search for clauses covering alterations, fixtures, windows, trim, and adhesive products.
• Building rules: Condominiums and managed apartments may regulate window coverings or visible items.
• Window responsibility: Confirm whether the tenant or owner handles glass, screens, and blind repairs.
• Permission needs: Ask in writing if the setup compresses trim, modifies a blind, or attaches beyond plain glass.
• Move-in records: Photograph existing scratches, failed seals, loose trim, or cracked caulk.

A common misconception is that asking the landlord automatically creates a problem. A narrow question—“May I use a removable suction-mounted cat bed on the interior glass without adhesive or drilling?”—often produces a clearer answer than a broad request to modify the window.

Why is a window perch valuable for an indoor cat?

A window seat can support observation, resting, climbing, and choice. Those are meaningful forms of indoor cat enrichment when the perch is stable and the cat can leave freely.

The AAFP and ISFM Feline Environmental Needs Guidelines identify safe resting areas, elevated spaces, play, and opportunities for predictable human-cat interaction as important environmental needs. A window perch can support several of these needs, but it should complement—not replace—play, scratching surfaces, hiding places, and floor-level beds.

Think of the perch as a balcony inside the home. The view is enriching, but the structure must be sound.

Which no-screw mount has the best Lease-Safe Enrichment Score?

No mount type wins for every rental. The best choice is the one that fits the window while controlling surface risk and supporting repeatable inspection.

Treat the score as a decision framework, not a certification. A freestanding bed may outperform a suction model in a historic apartment with wavy glass. A suction perch may be the cleaner option in a modern unit with a broad, smooth pane.

For low-cost configurations, the methodology in DIY Cat Window Seat: Easy Renter Hacks establishes a useful baseline: reversibility must be evaluated before appearance or price. That sequence inherently neutralizes many deposit risks associated with improvised fasteners.

How should renters install a no-screw cat perch without damage?

Concerned that one setup error could loosen a cup, mark the sill, trap a blind cord, or overheat the bed?
Use this damage-free installation workflow to inspect, prepare, test, document, and monitor the complete setup.

Safe installation begins before the perch touches the window. Inspect the supporting surface, remove nearby hazards, follow the manufacturer’s instructions, and load-test the assembled perch before your cat uses it.

We call this metric Damage-Free Installation Reliability. It assesses five controls:

• Surface preparation: The contact area is clean, compatible, and undamaged.
• Load testing: Weight is added gradually without shifting or seal loss.
• Cord control: Blind and shade cords are inaccessible.
• Heat management: Glass, fabric, and hardware remain within a comfortable range.
• Post-install inspection: The mount is checked after settling and during normal use.

What should you inspect before installation?

Start with the window itself. Do not use a damaged pane as a structural support point.

• Glass condition: Stop if you see cracks, chips near the edge, looseness, or movement in the frame.
• Glass surface: Check for texture, privacy coatings, aftermarket film, condensation, or persistent residue.
• Sill depth: Measure the flat usable surface, not the total trim width.
• Trim strength: Look for soft wood, peeling paint, loose molding, or brittle vinyl.
• Window operation: Confirm the perch will not block locks, emergency access, or required ventilation.
• Screen security: A screen is not a fall barrier for a cat leaning or jumping against it.
• Cord location: Remove dangling blind or shade cords from the perch zone.
• Sun exposure: Track direct sun and glass temperature during the hottest part of the day.
• Escape risk: Keep the window closed and locked unless a secure, cat-rated barrier is present.

The U.S. General Services Administration’s Historic Preservation Technical Procedures describe inspection and repair considerations for glazing and window components. The practical renter takeaway is simple: cracked, loose, or deteriorated glazing should be assessed before it carries any attached load.

How should glass be cleaned before mounting suction cups?

Clean glass improves suction cup reliability because grease, dust, soap, and lint create tiny air pathways under the cup. Those pathways act like a slow leak in a tire.

Follow the perch manufacturer’s manual first. If it permits ordinary glass preparation:

1. Clear the area: Remove curtains, cords, décor, and items from the sill.
2. Wash the contact zones: Use a residue-free glass-cleaning method approved for the pane.
3. Remove oily film: Pay special attention to cooking residue, smoke deposits, and pet nose marks.
4. Rinse if needed: Soap left on glass can reduce seal consistency.
5. Dry completely: Use a clean, lint-free cloth.
6. Inspect at an angle: Side lighting makes streaks and film easier to see.
7. Clean the cups: Follow the manufacturer’s directions for washing or softening them.
8. Mount promptly: Avoid touching the cleaned contact zones with your fingers.

Do not assume more moisture creates a better long-term seal. Some manuals call for a lightly dampened cup; others require a dry surface. Strict adherence to the supplied instructions is the standardized evaluation point.

How do you install each mount type safely?

For a suction cup cat window perch

• Position all cups on plain glass: Keep cup edges away from frames, seams, film edges, and textured areas.
• Lock each mechanism fully: Twist-lock or lever-lock systems must reach the maker’s specified position.
• Check cup shape: Replace cups that are cracked, hardened, warped, or permanently curled.
• Align support cables: Cables should carry load evenly without rubbing sharp frame edges.
• Press-test the frame: Apply light downward and sideways pressure before adding test weight.

When evaluating seal redundancy rather than advertised capacity alone, a four-point twist-lock configuration provides a clearer inspection baseline because each contact point can be checked separately. The Secure & Stylish Cat Window Perch Hammock uses four twist-lock suction cups, breathable fabric, and a machine-washable bed.

Those features do not remove the need for compatible glass or daily checks. They establish an architectural standard for what renters should verify: independently lockable contact points, washable contact fabric, and a mount that remains visible for inspection.

For a sill clamp perch

• Measure usable depth: Confirm that the clamp reaches a solid, flat area.
• Protect the finish: Use only manufacturer-approved pads that cannot slip or stain.
• Tighten evenly: Stop when the perch is secure; excessive force can dent trim.
• Check sash clearance: Open and close the window carefully if the design permits operation.
• Mark a reference point: A small removable visual marker can reveal gradual movement.

Never clamp onto loose molding, a thin decorative lip, or peeling paint. The clamp should load a structural sill area, not a cosmetic edge.

For a tension-supported or freestanding perch

• Confirm pressure surfaces: Tension feet need solid, level contact areas.
• Protect without improvising: Unapproved felt or foam can compress and reduce tension.
• Stabilize the base: A freestanding bed should not rock when pressed from different directions.
• Control tipping: Position the heavier base side away from traffic and energetic launch paths.
• Preserve egress: Do not obstruct doors, fire escapes, or a required exit window.

Freestanding designs are often the quantitative baseline for extremely low surface risk. Their tradeoff is floor space and possible tipping, especially with large cats that leap from nearby furniture.

How can blind cords be made safer?

Blind cords should be removed from the cat’s reach, not simply tucked loosely behind the perch. Loops and dangling cords can create strangulation hazards.

The U.S. Consumer Product Safety Commission identifies corded window coverings as a strangulation risk and advises choosing cordless products where possible. Although the agency’s core warnings focus on children, the same physical hazard—an accessible loop near a resting or jumping area—also deserves attention in a pet setup.

Use these controls:

• Cordless coverings: This is the cleanest option where replacement is permitted.
• Fixed tension devices: Use approved devices installed according to their instructions.
• High cord storage: Keep every loop and pull beyond the cat’s standing and jumping reach.
• Curtain clearance: Prevent fabric from covering the cups or becoming trapped under the frame.
• Daily verification: Check that repeated blind use has not lowered a cord into the perch zone.

What does a renter-safe installation checklist look like?

What is a practical renter-safe install walkthrough?

Use books, sealed water containers, or exercise weights that can be secured from sliding. Never use breakable items.

1. Photograph the area: Capture the pane, frame, sill, blinds, cords, and existing marks.
2. Inspect the window: Check the glass, sash, lock, screen, trim, and caulk.
3. Measure the mount zone: Compare the dimensions with the manufacturer’s requirements.
4. Clean the contact points: Prepare the glass or sill exactly as directed.
5. Assemble on the floor: Confirm that fabric, frame pieces, cables, and locks are correctly seated.
6. Install the perch: Engage every cup, clamp, or tension point evenly.
7. Apply hand pressure: Press downward and sideways while watching for movement.
8. Add test weight gradually: Increase the load in small stages.
9. Wait and recheck: Look for cup-edge lifting, clamp movement, frame flex, or unusual sounds.
10. Run a supervised trial: Observe your cat’s approach, jump angle, turning behavior, and exit.
11. Monitor for 24 hours: Recheck after direct sun, cooler nighttime temperatures, and blind use.
12. Allow routine use: Continue daily checks and scheduled cleaning.

Do this before your cat uses it unsupervised. A successful five-minute test is helpful, but it cannot reproduce a full cycle of sunlight, air-conditioning, nighttime cooling, and repeated jumping.

For model-specific fit and care, How to Install and Clean a Cat Window Perch provides the operational threshold: the perch should pass glass-fit, mounting, cleaning, and no-fit checks before routine use.

How do you know if the weight limit is safe enough?

Does a “50-pound capacity” mean a 50-pound cat can jump onto the perch safely?
This section converts manufacturer capacity into a practical Renter Safety Margin that accounts for movement, wear, installation quality, and multiple cats.

A listed weight capacity is the manufacturer’s stated maximum under specified conditions. It should not be treated as your target operating load. Your cat’s body weight is only one part of the real load.

Jumping, turning, wrestling, wet fabric, bedding, and a second cat can increase stress on the frame and mount. A static capacity does not automatically describe dynamic loading—force created by movement.

What is the Renter Safety Margin?

The Renter Safety Margin is the unused portion of the manufacturer’s verified capacity after counting every expected load.

Use this screening formula:

Total expected loaded weight should include:

• Cat weight: Use a recent veterinary or home scale reading.
• Second cat: Count another cat if shared access is realistically possible.
• Added bedding: Include blankets, pads, and washable liners.
• Accessory weight: Count toys or other attached items permitted by the manufacturer.
• Behavioral demand: Treat jumping and rough play as reasons to seek more unused capacity.

Example: a perch listed for 40 pounds carrying a 14-pound cat and a 2-pound pad has 24 pounds of unused stated capacity. That does not prove safety, but it gives more operating room than using the same perch for two 18-pound cats.

There is no universal government-approved percentage for cat-perch reserve capacity. Any fixed rule presented as guaranteed would be misleading.

For ordinary screening, we prefer keeping the expected static load at or below roughly 50% to 67% of the stated capacity, unless the manufacturer provides a different operating rule. This is a conservative house framework, not a substitute for the manual or product testing.

Why is jumping different from sleeping?

A sleeping cat applies a fairly steady load. A jumping cat transfers momentum over a short period, creating a load spike.

Think of standing on a bathroom scale versus hopping onto it. Your body weight has not changed, but the display can briefly rise because the force is dynamic.

Dynamic behavior includes:

• Direct jumping: The cat lands from the floor, sofa, or cat tree.
• Edge loading: The cat places most weight near one corner.
• Turning: The frame twists as the cat changes direction.
• Launching away: Rear paws push against the bed during exit.
• Shared use: One cat lands while another remains on the perch.
• Startle response: A noise causes a sudden, forceful departure.

This is why capacity should be benchmarked against likely behavior, not sleeping weight alone.

How should large cats, kittens, seniors, and multiple cats be assessed?

• Large cats: Favor a wide frame, low flex, clear manufacturer capacity, and substantial unused capacity.
• Multiple cats: Count the combined weight even if they “usually” take turns.
• Kittens: Expect climbing, chewing, bouncing, and attempts to enter from awkward angles.
• Senior cats: Reduce jump distance and provide a stable intermediate step.
• Cats with limited mobility: Choose a low, firm surface with an easy exit and veterinary guidance where needed.
• Highly active cats: Prioritize resistance to lateral movement and repeated impact.

For size-based comparisons, Best Cat Window Hammocks 2025: Size-Based Reviews supplies a standardized evaluation based on cat size, stated capacity, and design. That framework is more useful than sorting by headline capacity alone because it calibrates the output to the actual user.

What capacity claims should make you cautious?

• No test conditions: The listing gives a number without identifying mounting conditions.
• Conflicting numbers: The package, manual, and online listing show different limits.
• No replacement guidance: The maker provides no direction for worn cups or damaged cables.
• Missing compatibility rules: The listing does not identify suitable glass or sill dimensions.
• Ambiguous shared use: The capacity is high, but the frame is too narrow for two cats.
• Capacity treated as a guarantee: Safety depends on installation, condition, and inspection.

Industry consensus dictates that capacity must be read with its conditions. A large number unsupported by a standardized evaluation is weaker evidence than a lower number paired with clear mounting instructions and documented compatibility.

Which mount type fits your apartment window?

Unsure whether your pane, sill, blinds, or trim can support a no-drill cat window perch?
Use the Mount Compatibility Index to reject poor fits before spending money or risking damage.

The best mount is determined by the supporting surface. The Mount Compatibility Index compares glass condition, sill geometry, trim strength, floor clearance, blind interference, and window operation.

Score each candidate as compatible, conditionally compatible, or incompatible. One critical failure—such as cracked glass or an unstable sill—should override a strong score elsewhere.

Window compatibility matrix by opening style

Which mount is best for a typical modern apartment window?

A suction cup cat window perch often fits a modern apartment with smooth, intact glass and enough unobstructed pane area. It offers high reversibility and leaves trim unloaded.

Its reliability still depends on:

• Correct glass: No texture, incompatible coating, crack, or loose pane.
• Cup condition: Flexible, clean cups without edge damage.
• Even engagement: Every locking point is fully seated.
• Temperature monitoring: Sun exposure does not cause recurring seal loss.
• Daily visibility: Curtains do not hide the mount from inspection.

When is a freestanding window bed the safer choice?

Choose freestanding support when the window itself fails compatibility checks. It often yields an optimal configuration for historic glass, narrow sills, film-covered panes, or lease terms that prohibit attachment.

Place it close enough for viewing but far enough from the glass to avoid trapping heat. The base should stay level and outside busy walking paths.

A common misconception is that freestanding automatically means stable. Tall, narrow furniture can tip. Test rocking, turning, and launch forces just as you would test a mounted perch.

What is the 60-second daily perch safety check?

Do you need to dismantle the perch every day to know it is secure?
No. A focused 60-second inspection can identify the most common signs of seal loss, shifting, wear, heat, and cord exposure.

Check the perch before the cat’s longest resting period and after major temperature changes. Remove the cat first if anything looks different.

Use the CUPS SAFE check:

A 60-second check works because it focuses on the performance degradation curve—the pattern by which cups harden, clamps migrate, fabric stretches, and cables fray over time.

Schedule a deeper inspection weekly and after:

• Window cleaning: Cleaner overspray may reach the cups.
• Extreme heat or cold: Temperature changes may affect materials and seals.
• A hard landing: Sudden impact can shift a mount.
• Multiple-cat use: Shared use can exceed the usual load.
• Perch washing: Reassembly errors may change cable or frame alignment.
• Moving the perch: Every new location requires a fresh compatibility and load test.

Why does a suction cup cat perch keep falling?

Frustrated because the cups hold for hours or days, then release without warning?
Most repeated failures trace to surface incompatibility, residue, damaged cups, uneven loading, temperature changes, or incorrect locking.

A falling suction perch is a failed setup until the cause is identified. Do not keep pressing the cups back onto the glass and allowing immediate use.

What are the most common causes of suction failure?

How should you troubleshoot repeated failures?

1. Remove the perch: Do not troubleshoot while the cat can access it.
2. Inspect the pane: Check for cracks, texture, film, moisture, and residue.
3. Inspect every cup: Look for nicks, stiffness, permanent warping, and contamination.
4. Review the manual: Confirm cleaning, moisture, placement, and locking requirements.
5. Reassemble completely: Uneven cables or reversed components can distort loading.
6. Move to verified glass: Test only if the new area meets all compatibility rules.
7. Load-test again: Repeat gradual loading and the 24-hour supervised trial.
8. Retire an unreliable setup: Switch to a sill clamp or freestanding perch if failure returns.

Repeated remounting does not fundamentally mitigate an incompatible surface. A different support method does.

Do not use household glue, double-sided tape, construction adhesive, screws, or improvised hardware to “strengthen” a suction product unless the manufacturer explicitly authorizes that configuration. Such changes can damage the rental surface and alter how the product carries weight.

How can renters manage sunlight, hot glass, curtains, and privacy?

Does the sunniest window automatically provide the best cat perch location?
A good location balances enrichment with temperature control, shade, privacy, cord safety, and unobstructed inspection.

Direct sun can turn a comfortable perch into a heat trap. Glass, dark fabric, and metal components may become much warmer than the surrounding room.

Observe the location across the day before choosing it permanently. Morning sun may be mild while late-afternoon exposure becomes intense.

• Provide choice: Keep a cooler resting place available away from the window.
• Create partial shade: Use cordless coverings without hiding the mount.
• Check surface heat: Test the fabric and nearby glass during peak sun.
• Maintain airflow: Avoid trapping the bed between heavy curtains and hot glass.
• Watch heat-sensitive cats: Seniors, kittens, flat-faced cats, and cats with medical conditions may need closer supervision.
• Keep water accessible: Place fresh water nearby without creating spill risk around the mount.

For apartments with recurring heat, DIY Cat Cooling Stations on a Budge provides a practical companion framework. If comparing cooling surfaces, Cooling Mats vs Water Beds for Cats benchmarks comfort, maintenance, durability, and cost rather than treating cooling as a single-feature purchase.

Privacy also matters. A ground-floor apartment may expose the cat to dogs, people, or outdoor cats at close range. If the view causes crouching, tail lashing, redirected aggression, or repeated alarm, move the perch or partially block the lower section of the window.

Which no-screw perch should a renter choose?

With so many designs and weight claims, what should actually decide the purchase?
Choose the model that passes compatibility, maintains unused capacity, supports inspection, and has the lowest credible rental-damage risk.

Start with the window, not the product listing. The buying sequence should be:

1. Reject incompatible mounts: Use the Mount Compatibility Index.
2. Calculate loaded weight: Include every cat and permitted accessory.
3. Preserve unused capacity: Apply the Renter Safety Margin.
4. Check installation evidence: Look for a clear manual, replacement guidance, and defined surface requirements.
5. Assess inspection access: Every cup, clamp, cable, and seam should remain visible.
6. Estimate total cost of ownership (TCO): Count replacement cups, fabric care, damaged blinds, and possible surface repairs.
7. Plan an alternative: Know which freestanding or sill-based option works if suction proves unsuitable.

Total cost of ownership (TCO) means the full cost across the product’s usable life, not simply the checkout price. A cheap perch that repeatedly falls, needs improvised repairs, or damages a blind has a poor TCO.

For a broader category comparison, the 2025 Cat Window Perch Safety & Design Guide provides the quantitative baseline for assessing mount design, renter fit, and safety features. For enrichment-focused context, Window Perch Wonders: A Must-Have for Cats explains how window observation can fit within a larger indoor environment.

The safest cat window perch with no screws is not the model with the largest headline number. It is the model whose mount matches the window, whose expected load stays comfortably below capacity, and whose condition can be checked every day.

What is the safest final decision for a renter?

Still worried that choosing incorrectly could put your cat, window, or deposit at risk?
Use compatibility, unused capacity, reversible installation, and daily inspection as the final decision standard.

A renter-friendly cat window perch should enrich the cat’s day without transferring hidden risk to the glass, trim, blinds, or lease. That outcome depends on the complete setup.

The best decision follows four rules:

• Match before buying: Use the compatibility matrix to eliminate unsuitable mounts.
• Leave capacity unused: Judge the real loaded weight, not the cat’s weight alone.
• Test before trust: Apply gradual weight and complete a supervised 24-hour trial.
• Inspect before use: Run the 60-second safety check each day.

This framework is benchmarked against the failure points renters can control: surface compatibility, installation quality, dynamic loading, heat, cord exposure, and wear.

Use the mount decision table before buying. Save or download the daily perch safety checklist before installation. If any critical factor fails, compare renter-safe perch types rather than forcing one model to fit an unsuitable window.

Frequently Asked Questions

Need a fast answer to a practical installation or buying question?
These answers cover the concerns renters most often face after comparing mount types.

Are suction cup cat window perches safe?

Can suction cups be trusted while a cat sleeps or jumps?
They can work reliably on compatible glass when installed, tested, and inspected correctly.

A suction cup cat window perch can be suitable on smooth, intact, clean glass. Safety depends on cup condition, correct locking, even loading, temperature, and daily inspection.

Do not use suction cups on textured glass, damaged panes, or incompatible window film. Stop use if a cup repeatedly loosens.

Can a cat window perch crack the glass?

Could mounting or jumping damage the pane?
Risk is reduced by using intact compatible glass, following placement rules, and rejecting damaged windows.

Any loaded attachment can create stress. Do not mount on cracked, chipped, loose, or visibly deteriorated glass. Keep suction cups in the manufacturer-approved area and away from unsupported edges or seams.

If the glass moves, rattles, or shows damage, use a freestanding bed and report the condition to the property manager.

How much safety margin should a cat perch have?

How far below the listed capacity should the real load stay?
Aim for substantial unused capacity rather than treating the limit as an operating target.

As a conservative screening approach, keep expected static load around 50% to 67% of stated capacity when practical. This is not a universal certification or guarantee.

Count all cats, bedding, and approved accessories. Seek more unused capacity for jumping, shared use, large cats, or energetic kittens.

Can two cats share one window hammock?

What if the cats usually take turns but occasionally pile in together?
Assess the setup using their combined weight and shared movement.

Two cats should share a perch only if the manufacturer permits it, the bed has enough usable space, and the combined load preserves a practical safety margin.

Shared use creates edge loading, movement, and surprise landings. If you cannot control access, calculate for both cats every time.

How often should suction cups be cleaned or replaced?

Is daily removal necessary to keep the mount secure?
No fixed schedule fits every product, so follow the manual and inspect the cups daily.

Clean the cups whenever residue, dust, condensation, or seal problems appear. Replace them if they become cracked, stiff, warped, or unable to hold after correct cleaning and installation.

Do not substitute generic cups unless the manufacturer confirms compatibility.

Is a sill-clamp perch safer than a suction perch?

Would a clamp remove the risk of suction failure?
It removes dependence on glass suction but creates different requirements.

A sill clamp may be the safer choice for a deep, solid sill with durable trim. It may be a poor choice for narrow ledges, soft wood, peeling paint, loose molding, or windows that must remain operable.

The safer mount is the compatible one, not one mount type in isolation.

Can I place a window perch over blinds?

Can blinds stay behind the bed for privacy?
Only if cords, slats, fabric, and operating hardware remain clear of the cat and mount.

Never allow blind cords or loops to cross the bed or jump path. Blinds should not conceal suction cups or pull against support cables.

Cordless coverings provide the cleanest setup. If safe clearance cannot be maintained, relocate the perch.

What should I do if the perch falls once?

Is one fall simply a cue to press the cups back on?
Treat every fall as a setup failure that requires a complete inspection and new load test.

Remove cat access, inspect the window and every component, review the manual, clean approved surfaces, and identify the cause. Repeat gradual load testing and a supervised 24-hour trial.

If the failure repeats, retire that configuration and use another mount type.