Threshold Clearance: A Beginner's Guide

⚡ Quick Answer: Threshold clearance is the maximum height of a raised edge or transition strip that a robot vacuum can climb over without getting stuck. Most robots handle 15-20mm, but anything taller will stop them cold. If your home has tall doorway strips or transition bumps between rooms, this spec determines which areas get cleaned automatically. You can often solve this by replacing tall strips with low-profile ramps rather than buying an expensive robot.

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✨ Quick Takeaways

• 🚧 Threshold clearance is the maximum height bump a robot vacuum can climb over — most robots handle 15-20mm, and anything taller will stop them dead.
• 🏠 If your home has transition strips between rooms (carpet to tile, bathroom lips, conservatory edges), clearance directly affects which rooms get cleaned.
• 🛠️ Before buying an expensive high-clearance robot, check if you can swap tall threshold strips for low-profile ramps — a £10 fix beats a £500 robot upgrade.
• 🐢 Robot wheels are small and close together like a tortoise stepping over a kerb — even 2mm too tall and the wheels just spin helplessly.
• ✅ In newer builds with uniform flooring and no strips, threshold clearance won't matter at all to your cleaning routine.

❓ Frequently Asked Questions

What height threshold can most robot vacuums handle?

Most robot vacuums can climb over thresholds between 15mm and 20mm tall. Anything higher and the robot will get stuck, reverse, and eventually give up.

Will my robot vacuum get stuck on door strips?

Yes, if your doorway has a raised transition strip taller than your robot's clearance rating, it will treat it like a wall and won't cross into that room. You'd need to manually move it or swap the strip for a lower-profile ramp.

Can I fix high thresholds without buying a new robot?

Absolutely. You can replace tall, square-edged threshold strips with sloped ramps from a DIY shop (usually a few pounds), or use low-profile rubber ramps — this is often cheaper than upgrading to a more expensive robot.

Do I need high threshold clearance if I have all the same flooring?

No. If your home has uniform flooring throughout with no raised strips or transitions between rooms, threshold clearance won't affect you at all.

Why can't robots just roll over tall thresholds?

Robot vacuum wheels are small and positioned close together like a tortoise's legs. If a threshold is even slightly too tall, the chassis hits it first and the wheels just spin without getting traction to climb over.

How is threshold clearance measured?

Manufacturers measure it in millimetres, and it represents the maximum height bump the robot's wheels can successfully climb without the chassis getting stuck.

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If you've ever ordered a robot vacuum online, excitedly unboxed it, set it going — and then watched it bump helplessly against the little raised metal strip in your doorway and give up, you'll know exactly why threshold clearance matters. That tiny strip between your kitchen tiles and your hallway carpet? Your robot either sails over it like a champ, or treats it like an unclimbable wall. This is the feature that answers the question: can my robot actually get from one room to another on its own?

The good news is that once someone explains it, threshold clearance is one of the simplest specs to understand. There are no complicated numbers to memorise, no engineer-speak required. It basically comes down to one question: how tall is the bump between your rooms, and can your robot's little wheels get over it? That's it. Let's break it down properly so you know exactly what to look for before you buy.

So what actually is Threshold / step clearance?

Threshold clearance — sometimes called step clearance — is simply the maximum height of a bump or raised strip that a robot vacuum can climb over without getting stuck. Every robot vacuum has a limit, and manufacturers measure it in millimetres. Most robots can handle somewhere between 15mm and 20mm. If the raised door strip in your home is taller than your robot's clearance limit, the robot will hit it, reverse, try again, fail, and eventually give up and go home to its charging dock — having missed an entire room's worth of floors.

How does it work?

Robot vacuums sit quite low to the ground, and their wheels are small and close together — think of a little tortoise trying to step over a kerb. When it rolls toward a raised threshold strip (that's the flat or angled bar fitted in the gap between two types of flooring), the front of the robot makes contact before the wheels reach the base of the obstacle. If the strip is within the robot's clearance rating, its motors give the wheels just enough power and the chassis is shaped in a way that lets it roll up and over smoothly. If the strip is even a couple of millimetres too tall, it's like asking that tortoise to climb a wall — the wheels just spin and the robot goes nowhere. Some newer robots have larger, rubberised wheels with a more angled front edge specifically designed to tackle taller thresholds.

Why does it matter for your home?

In a single-floor home where all your rooms are connected by flat, open doorways with no strips at all, threshold clearance simply won't affect your life one bit. But in the real world — especially in older UK homes — there are often transition strips between carpet and hard floors, slightly raised bathroom thresholds, or even a small lip at a conservatory entrance. If your robot can't clear these, it can only ever clean one zone of your home per session, which means you're either manually moving it from room to room (completely defeating the point) or some rooms just never get done. For a lot of buyers, this is the difference between a robot that genuinely cleans the whole house and one that just does the living room.

How does it compare to the alternative?

The main alternative to relying on the robot's wheel height and chassis shape is to simply rearrange or remove the problem. Some people swap out tall, square-edged threshold strips for low, ramped transition strips (the kind that slope gently up and back down) which even a modest robot can handle easily. Others lay a small ramp of tape or a purpose-made rubber ramp in the doorway. This is a surprisingly cheap and effective fix — a pack of low-profile transition strips from a DIY shop costs just a few pounds and can save you from needing to buy a pricier robot with heavy-duty wheels. If you're happy to do a little home prep, you don't necessarily need to pay extra for top-end clearance specs.

Do you actually need it?

If you live in a newer build or a flat where all the floors are the same height throughout with no strips between rooms, you can honestly ignore this spec entirely and save yourself the research. But if you have mixed flooring — say, carpet in the lounge and tiles in the kitchen — there's a good chance you have threshold strips, and it's worth getting down on your hands and knees with a ruler before you buy. Measure the tallest strip in your home. If it's over 15mm, look for a robot rated at 18mm or 20mm clearance. If you have pets and the robot needs to roam the whole house unsupervised every day, a higher clearance rating is genuinely worth the small extra cost. If you're only cleaning one room, don't bother.

Which robot vacuums have Threshold / step clearance?

The bottom line

Threshold clearance is one of those specs that sounds technical but is actually very practical and easy to check. Before you buy any robot vacuum, spend two minutes measuring the highest door strip in your home. If everything is under 15mm, almost any robot will do the job. If you've got taller strips — common in older homes with thick carpets meeting tiled floors — look for a model rated at 18mm or 20mm and you'll be absolutely fine. It's not a premium luxury feature, it's just a matter of matching the robot to your actual home. A little measuring now saves a lot of frustration later.