Narrowboat Mattress Sizes: Complete Guide

Choosing the right mattress for a narrowboat is not always as simple as buying a standard bed for a house. Space is tighter, walls can curve, corners may need shaping, and access through doors and hatches can be awkward.

This guide explains the most common narrowboat mattress sizes, how different bed layouts affect your options, and what to measure before ordering. Whether you are refitting a boat, replacing an old mattress, or planning your first liveaboard set-up, the aim is to help you sleep comfortably without wasting valuable cabin space.

Why Narrowboat Mattress Sizes Are Different

A narrowboat is usually built around practical use of space. Every cupboard, step, seat and bed has to earn its place. Because of this, beds are often fitted into spaces that would be unusual in a house.

Some narrowboats use standard UK mattress dimensions, but many do not. A mattress might need to be shorter than normal, narrower than a domestic double, split into sections, or shaped to fit around the hull.

Common reasons for non-standard narrowboat mattress sizes include:

• Limited cabin width, especially beside corridors and cupboards.
• Curved hull sides that reduce usable mattress width at the edges.
• Cross beds that fold away during the day.
• Dinette beds made from cushions rather than a single mattress.
• Fixed beds built over storage, water tanks, or equipment.
• Need for rounded or angled corners to improve access.

For this reason, measuring carefully is more important than assuming a shop-bought mattress will fit.

Standard UK Mattress Sizes for Reference

Before looking at narrowboat-specific options, it helps to know standard UK mattress sizes. These are commonly available from high street and online retailers.

• Small single: 75cm x 190cm, or 2ft 6in x 6ft 3in.
• Single: 90cm x 190cm, or 3ft x 6ft 3in.
• Small double: 120cm x 190cm, or 4ft x 6ft 3in.
• Double: 135cm x 190cm, or 4ft 6in x 6ft 3in.
• King size: 150cm x 200cm, or 5ft x 6ft 6in.
• Super king: 180cm x 200cm, or 6ft x 6ft 6in.

On a narrowboat, the small double and standard double are often the most relevant sizes. A king size mattress is rarely practical unless the boat has a particularly generous or cleverly designed sleeping area.

Common Narrowboat Mattress Sizes

There is no single official narrowboat mattress size. Boats vary by builder, age, refit history and layout. However, there are several sizes and styles that appear frequently.

Fixed Double Mattress

A fixed double is a popular choice for liveaboards and regular cruisers. It is usually positioned lengthways along the boat, often with one side against the cabin wall.

The mattress may be close to a standard UK double at 135cm x 190cm, but many are narrower. A width of around 120cm to 130cm is common where walkway space is needed.

Practical points to consider:

• A standard double may fit the base but leave little room to walk past.
• A slightly narrower mattress can make the cabin feel much easier to use.
• If one side is against a wall, think about how easy it will be to make the bed.
• Check whether the mattress needs a cut corner near the foot for access.

Cross Bed Mattress

A cross bed runs across the width of the narrowboat rather than along its length. This can allow a wider sleeping surface at night, while still leaving a walkway when the bed is folded or slid away.

Cross beds often use a mattress in two or more sections. One section stays fixed, while another slides out, folds over, or lifts into position.

Because the mattress spans the boat, the available length depends on the internal cabin width. This means the sleeping length can be shorter than a standard 190cm mattress unless the design includes an extension or recess.

When ordering a cross bed mattress, it is particularly important to measure:

• The total sleeping width when the bed is fully extended.
• The length from wall to wall at mattress height.
• The size of each individual mattress section.
• Where any joins will sit when you are lying down.
• Whether the sections need fabric hinges or separate covers.

Small Double Mattress

A small double, also called a 4ft mattress, is one of the most useful sizes on a narrowboat. At 120cm wide, it provides more comfort than a single but takes up less room than a standard double.

This size can work well in guest cabins, compact master cabins, and boats where you want to preserve walkway space. It is also easier to manoeuvre through the boat than a larger mattress.

For solo sleepers, a small double can feel generous without dominating the cabin. For two adults, it may be cosy, but still workable for many boat layouts.

Single and Bunk Mattresses

Single beds and bunks are common on family boats, hire-style layouts and boats with convertible sleeping areas. A standard single is 90cm x 190cm, but narrowboat bunks are often slimmer.

Some bunk mattresses are closer to small single dimensions, especially where they are fitted into a cabin side or above another berth. Always measure the base rather than relying on the old mattress, as older foam can compress or distort over time.

For children, a narrower bunk may be perfectly adequate. For adults, the extra width of a standard single is usually more comfortable if the layout allows it.

Dinette Mattress Cushions

Many narrowboats have a dinette that converts into a bed. In this arrangement, the seats and backrests become the sleeping surface, supported by a lowered table or pull-out frame.

Dinette beds are usually made from several cushions rather than one mattress. The exact dimensions depend entirely on the furniture design.

If you are improving a dinette bed, consider whether you need new foam cushions, a mattress topper, or a custom folding mattress. A topper can help smooth out cushion joins, but it still needs somewhere to be stored during the day.

How to Measure for a Narrowboat Mattress

Accurate measuring is the most important part of buying a narrowboat mattress. A difference of just a few centimetres can make a mattress difficult to fit, awkward to lift, or uncomfortable to use.

Use a tape measure, write everything down, and measure more than once. If possible, take photos of the bed base and mark the dimensions on a simple sketch.

Measure the Bed Base, Not Just the Old Mattress

An old mattress may not be the right guide. It could have shrunk, sagged, compressed, or been the wrong size in the first place. Measure the actual platform, frame, or cushion space.

Record the maximum length and width, but also note where the mattress should sit. Sometimes a mattress should be slightly smaller than the base so it can be lifted easily or tucked under trim.

Check Width at Different Points

Narrowboat walls are not always straight from floor to ceiling. The hull may curve inwards, especially near the side of a fixed bed. Measure the width at mattress height, not just at the top of the bed base.

If the bed is against the hull, check whether the mattress edge will press into lining, pipework, shelves, or window surrounds.

Allow for Bedding

A mattress that fits tightly into a recess may seem fine until you add a sheet, mattress protector and duvet. Leave enough space to tuck bedding in and lift the mattress for ventilation.

This is especially important for fixed beds in corners, where access is limited on one or two sides.

Think About Access Through the Boat

Before ordering a full-size mattress, consider whether you can get it into the cabin. Narrowboat doorways, steps, bulkheads and tight turns can make delivery challenging.

Foam mattresses are often easier to bend slightly than sprung mattresses, but you should still check with the supplier. For awkward access, a split mattress or folding design may be the safest option.

Shaped and Made-to-Measure Mattresses

Many boat owners choose a made-to-measure mattress because it solves problems that standard sizes cannot. Custom mattresses can be made to a specific length, width, depth and shape.

Useful custom options include:

• Cut corners to improve walkway access or fit around furniture.
• Rounded corners for a neater fit in tight spaces.
• Split sections for cross beds, lifting bases, or easier handling.
• Reduced length for compact cabins.
• Custom depth where headroom or storage access matters.

If you need a shaped mattress, provide a clear template or drawing. For complex shapes, some suppliers recommend making a paper or cardboard template. This can help avoid confusion over which corner is being cut.

When drawing a template, mark the top side, head end, foot end, and any wall side. It is very easy to mirror a shape by mistake if the plan is not labelled clearly.

Choosing the Right Mattress Type

Size is only part of the decision. The mattress also needs to suit the way you use the boat, your comfort preferences, and the damp environment that can come with life afloat.

Foam Mattresses

Foam is a common choice for narrowboats because it can be cut to shape and made in different depths. It is also useful for bunks, dinettes and folding beds.

Higher quality foam tends to offer better support and last longer than very cheap foam. If the mattress will be used every night, it is worth choosing a suitable grade rather than the thinnest option available.

Memory Foam

Memory foam can feel comfortable and pressure-relieving, especially for side sleepers. However, it can also feel warmer than other materials and may need good ventilation underneath.

On a narrowboat, avoid placing memory foam directly on a solid, unventilated board without thinking about airflow. A breathable underlay, slatted base, or ventilation mat can help reduce moisture build-up.

Pocket Sprung Mattresses

Pocket sprung mattresses can provide excellent support, but they are less easy to bend, fold, or cut to unusual shapes. They may suit a fixed bed with straightforward access.

If you want a sprung mattress for a boat, check the finished size carefully and ask whether the manufacturer can produce the exact dimensions you need.

Hybrid Mattresses

Hybrid mattresses combine springs with foam or other comfort layers. They can be comfortable for everyday use, but may be heavier and less flexible than all-foam options.

Weight matters on a narrowboat, especially if you need to lift the mattress to reach storage beneath. Consider whether you can manage it easily.

Mattress Depth on a Narrowboat

Domestic mattresses can be quite deep, but thicker is not always better on a boat. A deep mattress may reduce headroom, block a window, make a bunk feel cramped, or stop a storage lid opening properly.

For fixed double beds, a medium-depth mattress can work well if there is enough room. For bunks, dinettes and folding beds, a thinner mattress or cushion-style foam may be more practical.

Before choosing depth, check:

• How much headroom you have when sitting up.
• Whether the mattress affects nearby drawers or cupboard doors.
• Whether under-bed storage can still be accessed.
• How heavy the mattress will be to lift.
• Whether fitted sheets are easy to source for that depth.

Ventilation and Moisture Control

Mattresses on boats need airflow. Warm air, cool surfaces and limited ventilation can create condensation, particularly under mattresses on solid bases.

Good ventilation helps keep the sleeping area fresher and can extend the life of the mattress. It is not just about comfort, but also about protecting the bed base and surrounding woodwork.

Practical steps include:

• Use slats where the bed design allows.
• Add a breathable mattress underlay or ventilation mat.
• Lift the mattress regularly to air the base.
• Avoid pushing bedding hard against cold hull sides.
• Open windows, mushrooms or vents when conditions allow.
• Use a mattress protector that is breathable as well as protective.

If the mattress sits directly above storage, make sure the storage area is also ventilated. Damp items under a bed can affect the mattress above.

Bedding for Unusual Narrowboat Mattress Sizes

Once you have chosen the mattress, think about bedding. Standard sheets may not fit neatly on a custom size, especially if the mattress is shorter, narrower, or shaped.

For simple non-standard sizes, stretchy jersey fitted sheets can be forgiving. Flat sheets are also useful because they can be tucked to suit the shape.

For shaped mattresses or split cross beds, you may prefer:

• Made-to-measure fitted sheets.
• Separate sheets for each mattress section.
• A mattress topper cut to the same shape.
• Elastic sheet straps to keep bedding in place.
• A duvet size chosen for the sleepers, not just the mattress width.

If the bed folds away, avoid bulky bedding that makes the mechanism difficult to use. Storage bags or vacuum bags can be helpful, provided the bedding is completely dry before being packed away.

Practical Buying Tips

Buying a narrowboat mattress is easier when you approach it as part of the whole cabin layout, not just as a standalone purchase.

Before placing an order, run through this checklist:

• Measure the bed base at least twice.
• Check the route from the boat entrance to the bedroom.
• Decide whether the mattress needs to bend, fold, or split.
• Allow room for sheets, protectors and lifting the mattress.
• Think about ventilation under and around the mattress.
• Check whether a standard size will genuinely work, or only nearly work.
• Confirm all custom dimensions in writing before ordering.

If you are refitting the bedroom, decide on the mattress size before finalising cupboards, shelves and walkways. It is much easier to design around a comfortable bed than to squeeze a mattress into a space left over at the end.

Frequently Asked Questions

What is the most common narrowboat mattress size?

There is no single standard size, but small double and compact double mattresses are common. Many fixed beds use something close to 120cm to 135cm wide by 190cm long, depending on the cabin layout. Always measure your own bed base before buying.

Can I use a normal double mattress on a narrowboat?

Sometimes, yes. A standard UK double is 135cm x 190cm, and it may fit some fixed beds. However, it can be too wide for cabins with limited walkway space or curved sides. Check both the bed base and the access route into the boat.

Is a foam mattress better for a narrowboat?

Foam is often practical because it can be cut to size, shaped, split, and made in different depths. That does not automatically make it best for everyone. Comfort, support, ventilation and how often the bed is used should all guide your choice.

How thick should a narrowboat mattress be?

The best depth depends on the bed type. A fixed everyday bed can usually take a deeper mattress than a bunk, dinette or folding cross bed. Make sure there is enough headroom, storage access and ventilation before choosing a thick mattress.

Do I need a made-to-measure narrowboat mattress?

You may not need one if a standard size fits properly and can be delivered into the cabin. A made-to-measure mattress is worth considering if your bed is an unusual size, has shaped corners, folds away, or sits in a tight space where every centimetre matters.

A well-sized mattress can make a narrowboat feel far more comfortable and practical. Measure carefully, plan for airflow, and choose a design that suits both your sleeping habits and the realities of life aboard.