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Mattress Support Cores

Every mattress includes two key components. The cover and topmost layers used for cushioning are known as the comfort layers, while the supportive materials that constitute the bed’s base layer(s) are collectively known as the support core. The support core’s main purpose is to reinforce the rest of the mattress. This helps reduce sagging, indentations, and other forms of wear and tear in the sleep surface, and also minimizes sinkage along the edges where people normally sit. The support core also plays a role in temperature neutrality, noise, and durability, and may also help determine the bed’s price-point.

Several types of support cores are found in mattresses made today. This guide discusses common characteristics and functions of the most common support core materials.

Why Are Support Cores Important?

For most mattresses, the support core will make up most of the bed’s thickness profile. For example, a mattress with a 10″ profile will commonly have support core materials that measure between 6″ and 8″ thick.

Common Support Core Features

Though support core compositions vary, the following components are commonly found in today’s mattresses:

  1. The layer or layers between the comfort layers and the support core are known as transitional layers. Transitional layers provide a buffer that prevents the mattress from feeling excessively firm. Common transitional layers include high-density polyfoam, firm latex, or minicoils.
  2. Below the transitional layer(s) is the primary support core where the bulk of the bed’s supportive materials are housed. As we’ll discuss in the next section, the most common primary support core materials include metal springs, high-density foam, latex, or air chambers. With rare exception, the primary support core is usually the thickest mattress layer.
  3. In some mattresses – innersprings, hybrids, and airbeds, most commonly – the primary support core may be encased in high-density foam. This adds extra reinforcement to the bed, particularly around the perimeter where sinkage is likely to develop. Memory foam mattresses and latex mattresses are less likely to use foam encasements because their primary support core is already made of dense foam or foam-like material.
  4. Though not always included, many mattresses have a base layer to provide additional support. The base layer is almost always made of high-density polyfoam, and typically measures 2″ thick or less.

Why Are Support Cores so Important?

  • They prolong the bed’s lifespan: A good support core will bolster the entire bed and prevent excessive sagging or indentations from developing on the sleep surface. This can extend the lifespan of the mattress by a considerable margin, as early deterioration is one of the most common reasons for mattress replacements.
  • They alleviate aches and pains in sleepers: Uneven sleep surfaces are a common source of discomfort and strain in the back, hips, and other sensitive areas of the body. By helping the mattress maintain a uniform, sag-free surface, the support core can also help sleepers cut down on pain and pressure points.
  • They regulate mattress temperature: Support cores with strong air circulation, such as coils and ventilated latex layers, effectively cool down the entire mattress and help maintain a comfortable sleep temperature. This can be especially beneficial for sleepers who feel excessively hot or warm during the night.
  • They minimize motion transfer: Motion transfer occurs when someone shifts their sleep position or gets into/out of bed; their movement ripples across the mattress surface and may be felt in other areas of the bed. Support core materials can help the mattress absorb and isolate motion transfer; this can be very helpful for couples.
  • They reduce noise potential: There was a time when most mattresses were constructed with steel coil support cores that made a fair amount of noise. However, most of today’s beds are much quieter by comparison. Mattresses with foam or latex support cores are virtually silent when bearing weight, while hybrids and innersprings with coils encased in cloth or fabric (also known as pocketed coils) are fairly quiet as well. However, the support cores found in most innersprings and airbeds are still considered somewhat loud and may cause sleep disruptions.

Next, we’ll look at the most common materials found in the support cores of mattresses sold today.

Common Support Core Materials

Coils

Innerspring mattresses with coil support cores were considered an industry standard at one point. They still represent roughly two-thirds of beds sold today, though other mattress types – namely memory foam and latex models – have become more popular with the recent rise of online ‘bed-in-a-box’ brands.

As a rule, innersprings have primary support cores that contain coils. Most mattress coils are produced from steel, then heated and cooled during a process known as tempering. Tempering improves the flexibility and durability of the coils; it is tied to ‘temper memory,’ which indicates how long an individual coil will be springy or bouncy.

Innerspring mattresses usually feature one of four coil types:

  • Bonnell coils are formed from steel in an hourglass shape. The coil’s top and bottom are threaded with wires known as helicals, which join neighboring coils together. Side coils may also be grafted to thick border wires for added stability. Bonnell coils are exceptionally durable and will not shift too much when bearing weight. For this reason, bonnell coils are frequently used in hotels, hospitals, and other establishments that serve high volumes of overnight guests.
  • Offset coils are also hourglass-shaped and joined together with helicals. Unlike bonnell coils, offset coils have a straightened bottom that creates a hinge-like effect when the coils are bearing weight. Double offset coils – which have straightened tops and bottoms – are a common variation, as are free-arm offset coils that are not helical-joined with neighboring coils. Offset coils can help mattresses withstand wear and tear, making them relatively durable; as a result, they are usually found in more expensive beds.
  • Continuous-wire coils are arranged in rows of individual wires. Side helicals connect each wire to its neighbors to create a trapezoidal shape. Continuous-wire coils are fairly durable, but they do not provide the same levels of support as other coil types; they are also quite rare. However, they are often found in relatively inexpensive beds.
  • Pocketed coils are found in some innersprings, but most commonly used in hybrid mattresses; by definition, a hybrid must contain comfort layers of memory foam and/or latex, as well as pocketed coils. Pocketed coils are encased in fabric or cloth; the encasement strands are joined to neighboring coils with hot glue. Because pocketed coils do not have helicals or wire extensions, mattresses built with them offer better motion isolation and do not make as much noise.

When evaluating coils and coil types, there are a few variables to consider. One is coil gauge, or thickness. High-gauge coils are thinner, whereas low-gauge coils are thicker; the gauge of most mattress coils falls between 12 (lowest/thickest) and 17 (highest/thinnest). Many innersprings and hybrids feature a multi-gauge, or zoned, support core; this means that thicker low-gauge coils are located beneath the heaviest areas of the sleeper’s body, such as the shoulders and midsection, while thinner high-gauge wires support the head, legs, and other lighter areas. For most sleepers, zoned support cores provide above-average pain and pressure relief.

The pitch, or angle of the coil in relation to the surface is also important for determining how soft or firm the mattress will feel. Additionally, the turns, or number of times the coil is wound, indicate how soft/firm the coils are and how supportive the mattress will feel.

Lastly, many innerspring and hybrid manufacturers list the exact number of coils found in the mattress; this is known as coil count. Most innersprings and hybrids contain between 300 and 1,000 individual coils, but the number may exceed 2,000. Although mattresses with higher coil counts tend to be more durable than those with fewer coils, this measurement is not necessarily tied to overall quality, longevity, and support. Bottom line: be sure to research the wire type, gauge(s), pitch, turns, and coil count before settling on a specific model.

With these measurements in mind, the table below provides a detailed breakdown of the four most common coil types.

Characteristic Bonnell Coils Offset Coils Continuous-wire Coils Pocketed Coils
Shape Hourglass Hourglass with 1-2 straightened ends Single wires arranged in rows Spiral, with a fabric encasement
Joining Agent Metal helicals and additional wire extensions Metal helicals Metal helicals Hot glue
Typical Gauge Low to high Medium to high Medium to high High
Typical Coil Count 400 to 600 600 to 2,000 400 to 800 800 to 1,200
Pros Durable
Responsive/good for sex
Common and inexpensive
Durable
Responsive/good for sex
Durable
Inexpensive
Relatively quiet
Common
Relatively quiet
Good motion isolation
Cons Loud
Minimal conforming
Loud
Uncommon
Expensive
Uncommon
Minimal support
Expensive
Less durable
Average Cost $ $$ $ $$$

Mattresses with coils have notable pros and cons. On the plus side, they usually offer the most responsiveness, making them good for sex. Most innersprings and hybrids also sleep relatively cool due to good air circulation through the coil layers, and their strong support systems make them suitable for heavier people and back or stomach sleepers. Additionally, innersprings often have low price-points compared to other mattress types. However, they do not offer as much conforming/pressure relief as mattresses with other support core materials, and longevity is usually average at best.

One thing to note: due to the influx of bed-in-a-box brands selling hybrids, most mattresses with coils sold online are built with pocketed coils. Bonnell, offset, and continuous-wire coils are much more common in brick-and-mortar mattress stores.

Mattresses with coil support cores may be suitable if:
  • You have a limited shopping budget
  • You tend to sleep hot
  • You weigh 130 pounds or more
  • You sleep on your back and/or stomach
Mattresses with coil support cores may not be suitable if:
  • You experience serious and/or chronic back pain
  • You and/or your sleep partner awaken easily due to movement or noise
  • You want to buy a mattress with a longer-than-average expected lifespan

Polyfoam

Flexible polyurethane foam, or polyfoam for short, is a synthetic material derived from petrochemicals. Polyfoam may be used in a bed’s comfort layers and/or support core, depending on how it is engineered. Denser, firmer foams make the best support cores; if the foam is too soft, then sleepers tend to sink excessively and permanent sagging is likely to develop in the sleep surface.

Polyfoam support cores are most commonly found in beds with polyfoam and/or memory foam comfort layers, as well as select mattresses with latex comfort layers. High-density foam is also used to create support core encasements, which are usually found in innersprings and hybrids, as well as the base layers used in all mattress types. Most transitional layers in mattresses are also made of polyfoam. Additionally, polyfoam mattress toppers are widely available.

Two factors are used to categorize polyfoam used in mattresses: density and compression modulus. Density is calculated by dividing the mass of an object by its volume; it is expressed in pounds per cubic foot, or PCF. Density indicates how much compression the foam can handle; it does not indicate how soft or firm it feels. Compression modulus represents a stress-to-strain ratio, and can be used to determine how much/little compression is needed to permanently change the foam’s overall structure.

Using these criteria, the polyfoam used in mattresses usually falls into one of three categories:

Polyfoam Type Density Range (PCF) Compression Modulus Range Used in… Availability Average Cost
Conventional 1.5 PCF or lower 1.8 to 2.0 Comfort layers Common $
High-density (HD) 1.5 to 2.4 PCF 2.1 to 2.3 Comfort layers and/or support cores Common $$
High-resiliency (HR) 2.5 PCF or higher 2.4 or higher Support cores Less common $$$

As a rule, high-resiliency (HR) polyfoam must have a density of at least 2.5 PCF and a compression modulus of 2.4.

Polyfoam support cores offer decent stability; the material isolates motion transfer very well and does not produce any noise when bearing weight. Generally speaking, mattresses with foam support cores are also among the least expensive options. However, the material tends to deteriorate somewhat quickly and does not offer the same resilient support as coils or latex. It also absorbs a fair amount of body heat from sleepers and may cause the bed to feel excessively warm as a result. This is especially true of mattresses that also have polyfoam and/or memory foam comfort layers.

Mattresses with polyfoam support cores may be suitable if:
  • You have a limited shopping budget
  • You experience serious and/or chronic pain
  • You and/or your sleep partner awaken easily due to movement or noise
Mattresses with polyfoam support cores may not be suitable if:
  • You tend to sleep hot
  • You want to buy a mattress with a longer-than-average expected lifespan

Latex

Latex is a material derived from the sap of rubber trees. Latex has many industrial uses due to its natural durability and flexibility. In recent years, it has become a common mattress component as well. Latex is also used to make other bedding accessories, such as pillows and mattress toppers.

Latex is produced using one of two processes. The Dunlop process, which involves molding and baking the rubber tree sap, yields latex with a dense, homogeneous structure; sediment typically gathers on the bottom, making the latex bottom-heavy. In the Talalay process, the sap is vacuum-sealed and deprived of oxygen before it is baked. As a result, Talalay latex is lighter and fluffier, and has a more heterogeneous structure. Dunlop and Talalay latex are both commonly used in mattress comfort layers. However, Dunlop latex is exclusively used in mattress support cores because it is denser and withstands compression better.

Another factor to consider is the ratio of natural to synthetic latex. Some mattresses are certified as having ‘100% organic latex.’ This means the latex has not been treated with any chemical fillers. ‘Natural latex’ indicates that the latex contains minimal fillers, ‘Blended latex’ indicates more fillers than natural latex, and ‘synthetic latex’ indicates that little to no natural latex is used. This factor is mostly a concern to eco-friendly shoppers, who usually prefer beds with organic or natural latex. Natural and organic latex also tend to sleep cooler. For this reason, beds with natural/organic latex tend to be more expensive than those with blended/synthetic latex.

A measurement known as indentation load deflection, or ILD, is used to evaluate the firmness of latex used in mattresses. To calculate ILD, place a circular disk measuring one foot (1′) in diameter on top of a section of latex that measures roughly four inches (4″) thick. The ILD is the amount of weight needed to compress the latex by 25%. ILD is expressed in numerals; the following table lists common ILD ranges for latex found in mattresses.

Firmness ILD Range Characteristics Found in…
Extra Soft 16 or lower Latex sinks to a considerable degree and conforms closely to the sleeper’s body Comfort layers
Soft 17 to 21 Latex sinks and conforms to a noticeable extent Comfort layers
Medium Soft to Medium 21 to 26 Latex sinks somewhat and conforms consistently Comfort layers
Medium Firm 27 to 31 Latex does not sink very much and conforms to a moderate extent Comfort layers and/or support core layers
Firm 32 to 36 Latex barely sinks and conforms to a minimal extent Support core layers
Extra Firm 37 or higher Latex does not sink and conforms very little, if at all Support core layers

Mattresses with latex support cores have several advantages. Because latex is so durable, most latex mattresses have much longer-than-average expected lifespans. The material also isolates motion fairly well – though polyfoam is generally better – and does not make any noise when bearing weight. Mattresses with natural and/or organic latex are also considered eco-friendly.

One common drawback of latex is that is sleeps somewhat warm. Some manufacturers remedy this problem by aerating the latex layers with tiny holes that allow air to circulate better. Breathable cover materials, such as organic cotton or rayon from bamboo, can also cool mattresses down; both of these materials are commonly used in the covers of latex mattresses. Additionally, latex can be quite heavy, making latex mattresses exceptionally difficult to lift and rotate. Price-point is another issue; the average all-latex mattress costs between $1,400 and $2,000.

Mattresses with latex support cores may be suitable if:
  • You experience serious and/or chronic pain
  • You and/or your sleep partner awaken easily due to movement or noise
  • You want to buy a mattress with a longer-than-average expected lifespan
Mattresses with latex support cores may not be suitable if:
  • You have a limited shopping budget
  • You tend to sleep hot
  • You want a mattress that is light and easy to lift

Air Chambers

Airbeds are popular among some sleepers because they offer high levels of personal customization. The beds are constructed with hollow air chambers (also known as bladders) in the support core. The chambers connect to an air pump, which brings in or releases air to make the mattress feel firmer or softer, respectively. Traditional airbeds require owners to adjust the chamber settings using manual controls, but many newer models can be adjusted using remote controls and/or wireless apps.

The number of chambers in an airbed is an important consideration. Many older airbeds have a single chamber that provides an even, level sleep surface. However, most newer airbed models have at least two air chambers – and some have eight or more. Another common variation is the tri-chamber design, which features individual chambers located beneath the sleeper’s head and neck, midsection, and legs. This allows sleepers to customize how much or little air supports these three individual areas of the body.

Airbeds are a great option for some sleepers, including those whose firmness preferences tend to fluctuate and people who experience aches and pains in isolated areas of their body. Many airbeds offer dual-firmness settings, allowing both sleepers to adjust the feel of their side. This design can be very beneficial for couples with differing preferences. The convenience of remote and app-based controls has endeared modern airbeds to many sleepers, as well.

However, airbed also have some notable downsides. They can be very loud, for one, and mechanical failures and breakdowns are somewhat common (though properly maintained airbeds have long expected lifespans). Those who sleep on multi-chamber airbeds also report sinkage in areas that fall between the chambers. Temperature neutrality is another issue; airbeds have a tendency to sleep excessively hot and/or excessively cold. They also carry the highest average price-point among all mattress types.

Mattresses with air chamber support cores may be suitable if:
  • Your firmness preferences vary from night to night
  • You and your sleep partner have different comfort preferences
  • You want to buy a mattress with a longer-than-average expected lifespan
Mattresses with air chamber support cores may not be suitable if:
  • You tend to sleep hot and/or cold
  • You and/or your sleep partner awaken easily due to noise
  • You have a limited shopping budget

Water Bladders

Waterbeds were a major craze among sleepers in the 1960s, ’70s, and ’80s. The fad has died down since, though a handful of manufacturers still produce waterbeds. Advances in technology have resulted in waterbeds that are more stable and customizable, as well.

Waterbeds fall into one of two categories. Hard-sided waterbeds are set inside a frame made of wood or another sturdy, resilient material, and placed on top of a platform. Alternatively, soft-sided waterbeds are placed in a foam frame and encased in fabric. For this reason, hard-sided waterbeds comprise the mattress and its support system; soft-sided beds require a foundation or base. This is important for buyers because hard-sided waterbeds are usually much cheaper than soft-sided models, making the latter a much larger financial investment.

Another component used to distinguish waterbeds is the internal structure. Like airbeds, waterbeds have bladders. Free flow waterbeds feature a single bladder, and often produce ripples and undulations across the sleep surface. Waveless waterbeds have multiple bladders; by containing and isolating the water, sleepers experience less rippling on the surface. Both free flow and waveless waterbeds can be heated or cooled; the temperature may be adjusted with manual, remote, and/or app-based controls.

Waterbeds offer decent pain and pressure relief for most. Unlike airbeds, which sink beneath sleepers, waterbeds cradle and conform to the sleeper’s body. This is particularly true for soft-sided waterbeds. Because waterbeds are often encased in vinyl or PVC, they are also very easy to clean compared to mattresses with fabric covers. Most waterbeds are also fairly inexpensive; soft-sided waterbeds tend to cost more than hard-sided models.

However, waterbeds also have several disadvantages. Most waterbeds – especially free flow models – do not isolate motion very well and can be quite noisy. They also tend to sleep excessively cool, though adjustable temperature settings can mitigate this issue to some extent. Waterbeds are also susceptible to leaks, punctures, and other types of damage that can compromise support and reduce the bed’s overall lifespan. Additionally, waterbeds are quite rare. And while the beds themselves are usually low-priced, operating and heating them can increase the sleeper’s utility costs.

Mattresses with water bladder support cores may be suitable if:
  • You experience serious and/or chronic pain
  • You enjoy rippling sensations on your sleep surface
  • You have a limited shopping budget
Mattresses with water bladder support cores may not be suitable if:
  • You and/or your sleep partner awaken easily due to movement or noise
  • You tend to sleep cool
  • You want to buy a mattress with a longer-than-average expected lifespan
  • You’re concerned about raising your utility costs

Performance Ratings for Support Core Materials

Now that we’ve discussed the most common support core materials, let’s see how they measure up to one another. The table below compares these materials based on durability, pain/pressure relief, temperature neutrality, and other buying factors. The ratings are based on verified customer and owner experiences, as well as intensive product research and analysis.

Criteria Coils Polyfoam Latex Air Chambers Water Bladders
Used in… Innerspring and hybrid mattresses Memory foam and latex mattresses (primary support core)
Innerspring, hybrid, and airbed mattresses (foam encasement and transitional/base layers)
Latex mattresses Airbeds Waterbeds
Durability Good to Very Good Fair to Good Very Good Good to Very Good Fair to Good
Conforming Fair to Good Good to Very Good Good to Very Good Very Good Fair to Good
Pain/Pressure Relief Fair to Good Good to Very Good Good to Very Good Very Good Fair to Good
Motion Isolation Poor to Good Good to Very Good Fair to Good Fair to Good Poor to Fair
Noise Potential Poor to Fair Very Good Very Good Poor Fair to Good
Temperature Neutrality Very Good Poor to Fair Good to Very Good Poor to Fair Fair to Good
Good for Sex? Very Good Poor to Fair Fair to Good Fair to Good Poor to Fair
Availability Common Common Somewhat common Rare Rare
Average Price-point $600 to $1,000 $800 to $1,200 $1,400 to $2,000 $2,200 and higher $700 to $1,300

Flippable Mattress Designs

Lastly, let’s discuss a growing trend in the mattress industry: flippable mattresses.

A flippable mattress is built with two comfort systems, one on each side, and a shared support core. Flippable mattresses usually have a different firmness setting on each side; to adjust the firmness, the sleeper simply flips the mattress over. Some flippable mattresses have the same firmness on each side; these beds are usually marketed as more durable because, when regularly rotated, the comfort layers won’t deteriorate as quickly.

Flippable beds are ideal for those whose firmness preferences fluctuate from night to night. However, their superior durability is questionable. Support cores bear most of the compression caused by the sleeper’s weight. Even when regularly rotated, the support core will still deteriorate at a normal pace. Therefore, a flippable mattress will not necessarily last longer than a one-sided model.

Additional Tuck Resources

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