What is a Bonnell Spring?

Hi Eddie.

Thanks for your question on what is a Bonnell sprung mattress. Bonnell springs go by many names such as open coil, cage sprung, Miracoil, Posture Tech and traditional spring, to name a few.

The Bonnell spring you refer to means it is a 13.5 gauge one-piece cage sprung mattress (open coil, not pocket springs). I had a quick scan for the item you mention and cannot find a double for the price you quote. This type of spring is the most basic possible in a mattress and is mass-produced.

The Bonnell or open coil spring unit is the cheapest and most ineffective support unit you can get in a mattress. It is a continuous piece of wire that is twisted and coiled to create a massive set of joined crude springs. This results in a one-size spring of sorts, which moves as a mass piece. So when you move, the whole bed ripples and shakes with you. There is mass transference and no isolation in the spring unit as it compresses. We have more detail here on why open coil mattresses should be avoided.

What exactly is a Bonnell spring and where does it come from?

The Bonnell spring dates back to the 19th century and was originally developed for use in horse-drawn carriage seats. The coil itself is hourglass-shaped: wider at the top and bottom, narrower in the middle. Multiple springs are linked together using a helical wire, and a thicker border wire runs around the perimeter to give some edge structure. The result is a single interconnected steel unit that behaves as one large, rigid mass rather than thousands of individual responsive components.

That is the core problem with any Bonnell spring mattress. When one spring compresses, it pulls on every spring connected to it. There is no independent response. There is no ability to match different areas of the body to different tensions. The whole unit moves together, which is why sleeping next to a partner on a Bonnell mattress means you feel every shift they make throughout the night.

Why a Bonnell spring mattress is a poor long-term choice

There are a few specific reasons we would always steer someone away from a Bonnell sprung mattress, regardless of budget.

The first is motion transfer. Because all the springs are physically joined, movement on one side of the bed travels across the entire unit. This is particularly disruptive for couples. With a pocket sprung mattress, each spring sits in its own individual fabric pocket and responds independently, so movement stays localised. With a Bonnell, that independence simply does not exist.

The second is the inability to match spring tension to body weight. A good pocket sprung mattress is made with springs of a specific gauge: the wire thickness that determines how much resistance the spring offers. Lighter sleepers need a finer gauge spring that responds to lower loads. Heavier sleepers need a firmer gauge that provides proper support without bottoming out. A Bonnell coil is a single gauge for everyone. It is a one-size-fits-all support system, which in practice means it fits nobody particularly well.

The third is longevity. Because the springs are interdependent, uneven wear in one area affects the behaviour of the springs around it. As the mattress softens, it softens unevenly and begins to form a trough. Natural fibre mattresses with calico pocket springs, by contrast, wear considerably more evenly because each spring responds only to the load directly above it.

Bonnell springs versus pocket springs: the key differences at a glance

If you want to understand this in more depth, our full guide to open coil versus pocket sprung mattresses covers each spring type in detail and explains why the step up to pocket springs makes such a significant difference in practice.

What about Bonnell springs versus memory foam?

This is a question we see regularly and it is worth addressing directly, because memory foam and Bonnell springs are the two most common mattress types found at the budget end of the market.

Memory foam has no springs at all. It uses a dense polyurethane foam that responds to heat and pressure, slowly moulding around the body. This is often marketed as a comfort feature, but it comes with significant drawbacks: memory foam retains body heat, which causes a large proportion of sleepers to overheat; it responds slowly so turning over in the night feels effortful; and because the foam breaks down at a cellular level over time, many memory foam mattresses are functionally worn out within five to six years.

A Bonnell spring mattress sits at a similar price point but with a very different feel. It is bouncy rather than moulding, and it breathes better than solid foam because air can circulate through the open spring unit. However, as we have described above, it transfers motion freely and provides no tailored support.

Neither is what we would recommend. Our full guide to pocket springs versus memory foam explains why a properly specified pocket sprung mattress with natural fibre upholstery outperforms both, and at what price points the difference starts to become genuinely meaningful.

What should you be looking for instead?

We only sell pocket spring mattresses and have never sold continuous coil mattresses. Pocket springs allow the most independent support, as each spring acts on its own rather than as one big rigid unit like the Bonnell. Pocket springs can also be tailored to your weight with specific spring gauges, whereas a Bonnell coil is nearly always the same gauge regardless of who is sleeping on it.

If you are starting to look at what to consider, our two most popular mattresses are a good place to begin. The Origins Pocket 1500 is our entry-level pocket spring mattress, made here in the UK with a 1,500-spring calico pocket spring unit and natural fibre upholstery. The Artisan Naturals steps up to a higher specification with a greater proportion of natural fibres, hand-tufted construction, and a two-sided build that substantially extends the mattress lifespan.

For a more detailed look at how to evaluate what is actually inside a mattress before you buy, our guide on how to choose a mattress is a good starting point. It walks through spring types, upholstery weights in GSM, and what questions to ask any retailer before committing.

Origins 1500 Pocket Spring Mattress

To help you with what to look for in a quality mattress, we would ask you to start by looking at the Origins 1500 mattress. When mattress shopping and working out how to choose a mattress, you need to start by asking exactly what is inside each mattress. The listing of this mattress will show you how to start uncovering what is inside a bed.

We do appreciate that if your budget is limited you should still be looking for the best you can get. We do have our outlet section where we sell returned mattresses for up to 40% off.

If you need more advice when looking for a new mattress then this video has all the insider tips that bed retailers try and keep hidden.

Why not call our friendly team on 0161 437 4419. You can find our office opening times here.

Kind regards, Gary