Start with the materials
Before getting into diaper styles, it helps to understand what the diaper is actually made from.
Every diaper system has two basic jobs:
Absorb moisture.
Keep that moisture contained.
Different materials handle those jobs differently.
Once you understand the fibres, the endless diaper terminology becomes much easier to follow.
Materials used for covers
PUL
PUL stands for polyurethane laminate.
It is fabric bonded with a thin polyurethane layer that creates a flexible waterproof barrier.
PUL is commonly used in:
- Pocket diapers
- All-in-one diapers
- All-in-two diapers
- Standalone diaper covers
PUL diapers and covers usually have elastic around the legs and waist to help create a snug fit and contain moisture and stool.
They commonly close with snaps or hook-and-loop.
Elastic is a working component and can eventually lose stretch or degrade. Snaps and hook-and-loop can also wear over time.
These extra components are also part of what makes PUL systems convenient and quick to put on.
Wool
Wool works differently from PUL.
It is not a laminated waterproof material.
When suitable wool is properly prepared and treated with lanolin, it becomes highly water-resistant.
The wool acts as the outer layer while the diaper underneath handles the absorbency.
There are several different types of wool covers, and the construction matters.
100% wool
Traditional 100% wool diaper covers generally require gentle care and are commonly hand washed.
Some wool fabrics also need to be intentionally felted or shrunk before or during their early use to reach the desired size, density, and water resistance.
Once the cover has reached the intended level of felting, care needs to be taken to avoid additional unwanted felting.
Heavy agitation and sudden temperature changes can continue shrinking and felting wool.
Wool with Lycra
Wool can also be blended with a small amount of Lycra for additional stretch and recovery.
The wool fabric we have made for Bumby is intentionally felted before the garment is sewn.
That means the fabric has already gone through the controlled shrinking and felting we want before it becomes a diaper cover.
Our wool contains a small amount of Lycra, generally around 3 to 5%.
That synthetic content is the tradeoff.
In return, we get a natural-fibre dominant cover with dependable stretch that can be machine washed according to its care instructions and lanolized as needed.
For families who want a natural cover without the more delicate care requirements of some traditional wool covers, this can make wool much more approachable.
Alpaca
Alpaca can also be used as a natural-fibre diaper cover.
It behaves similarly to wool in some ways, but it is not the same fibre.
Alpaca covers are not lanolized like wool covers.
Some alpaca fabrics may also need intentional felting or shrinking to create the density, fit, and water resistance needed for diapering.
Once that has been achieved, the same general concern applies. Continued heat changes or aggressive washing may create additional unwanted felting and shrinkage.
This means the exact fibre and construction of a natural cover matter.
"Wool" and "alpaca" do not automatically tell you how the finished cover should be cared for.
Always follow the instructions for the specific product.
Superwash wool
Superwash wool has been treated so that the fibre resists normal felting and shrinking.
That can be very useful for many garments.
For diaper covers, however, we do not consider superwash wool our preferred choice.
The treatment changes the natural behaviour of the wool fibre, while diaper covers rely on the characteristics of wool, controlled felting, and lanolin to create the performance we are looking for.
Absorbent fibres
Now we get to the material that actually holds the moisture.
Cotton, hemp, bamboo-based fabrics, microfibre, and blends all behave differently.
There is no perfect absorbent fibre.
Each has advantages and tradeoffs.
Cotton
Cotton absorbs moisture relatively quickly and is one of the most common natural fibres used in cloth diapers.
It can be found in flats, prefolds, preflats, contours, fitted diapers, inserts, and soakers.
Cotton also comes in many different fabric constructions, including jersey, interlock, fleece, terry, birdseye, and woven fabrics.
Two cotton diapers can therefore behave very differently.
Pros
- Natural fibre
- Absorbs relatively quickly
- Widely available
- Available in many weights and constructions
- Often relatively affordable
Cons
- May require more material than hemp for the same holding capacity
- Heavier cotton fabrics can become bulky
- Performance varies depending on the fabric construction and weight
Hemp
Hemp absorbs more slowly than cotton but can hold a significant amount of moisture.
That makes it popular when higher capacity is needed.
It can also be paired with a faster absorber such as cotton.
The cotton catches the initial wetting while the hemp provides additional holding capacity.
Pros
- High absorbent capacity
- Useful for heavy wetters
- Popular for naps and overnight
- Can add substantial absorbency without a large number of layers
Cons
- Slower to absorb than cotton
- Often works best with a faster absorber
- Can feel denser or firmer
- Usually costs more than basic cotton
Bamboo-based fabrics
Most soft bamboo diaper fabrics are manufactured cellulose textiles such as bamboo viscose or bamboo rayon.
The bamboo plant is the original cellulose source, but significant processing is required to turn it into the soft textile used in diapers.
These fabrics are often soft, stretchy, and comfortable.
Pros
- Very soft
- Often stretchy
- Good absorbent capacity
- Popular for fitted diapers and stretchy absorbency
Cons
- More processed than the word bamboo may suggest
- Fibre labels can be confusing
- Durability varies by fabric and blend
- Often combined with other fibres
Microfibre
Microfibre is a synthetic absorbent material commonly found in pocket diaper inserts.
It absorbs quickly and is relatively inexpensive.
It can also release moisture when compressed.
This is commonly called a compression leak.
Think of squeezing a wet sponge.
Pressure from sitting, car seats, tight clothing, or being carried can push some moisture back out.
Microfibre generally should not sit directly against the skin unless the product is specifically designed for that purpose.
Pros
- Fast absorption
- Lightweight
- Inexpensive
- Widely available
Cons
- Can be prone to compression leaks
- Synthetic
- Generally should not sit directly against the skin
- May behave differently from natural fibres when it comes to odour and buildup
Blends
Many absorbent fabrics combine fibres.
Cotton and hemp are a common combination.
Bamboo-based fabrics may be blended with cotton.
Stretchy fabrics may contain a small amount of spandex or Lycra.
Blends can be useful when each fibre contributes something specific, such as faster absorption, greater holding capacity, softness, or stretch.
More complicated does not automatically mean better.
The useful question is what each fibre is doing in the fabric.
What is 360° absorbency?
Absorbency does not have to sit only between the legs.
When an absorbent diaper wraps around the front, back, waist, hips, and sides, we refer to this as 360° absorbency.
Flats, prefolds, preflats, contours, and fitted diapers can all provide this type of coverage depending on how they are folded and fastened.
This can be especially useful when moisture travels away from the centre of the diaper during sleep, movement, or heavier wetting.
These diapers provide absorbency.
They still need a separate cover.
Diapers with PUL built in
Pocket diapers, all-in-ones, and all-in-twos use the same basic idea:
PUL on the outside with absorbency inside.
The main difference is where the absorbency sits and whether it comes out.
Pocket diapers
A pocket diaper has a PUL outer shell and a fabric lining.
Absorbent inserts are stuffed into an opening between those layers.
The lining sits against the skin while the absorbency sits inside the pocket.
Different types and amounts of absorbency can usually be used depending on what the wearer needs.
Once stuffed, the diaper goes on as one piece.
All-in-one diapers
An all-in-one, or AIO, has a PUL outer with the absorbency attached to the diaper.
The absorbent material sits against the wearer rather than being stuffed inside a pocket.
It may be sewn directly into the diaper or attached as absorbent flaps.
There is nothing separate to stuff or snap into place before use.
All-in-two diapers
An all-in-two, or AI2, has a PUL outer with removable absorbency that sits directly against the wearer.
The absorbent portion usually snaps into the shell or lays inside it.
When the absorbency is wet, it can be removed and replaced.
Depending on the system and whether the shell is still clean, the outer may be reused with fresh absorbency.
Wool and alpaca versions of these systems
You may also find wool or alpaca covers paired with attached, snap-in, or lay-in absorbency.
These can function similarly to an AIO or AI2.
Some families love these systems.
They are not our preferred approach.
Our concern is simply that the cover fibre and the absorbent fibre may not have the same care needs.
Wool, alpaca, cotton, hemp, bamboo-based fabrics, and synthetic absorbency are very different materials.
Permanently attaching them or treating them as one washable piece may require compromising how one of those fibres is cared for.
We prefer keeping natural-fibre covers and absorbency separate so each piece can be cared for according to what it actually needs.
That is our preference based on fibre care, not a declaration that the other system is wrong.
360° absorbency styles
Flats or Preflats
A flat is a large square or rectangle of absorbent fabric.
It is folded around the body in different ways depending on where absorbency is needed.
When wrapped around the body, a flat can provide 360° absorbency.
It can also be pad-folded into a rectangle and placed inside a cover. In that setup, the absorbency is concentrated more through the centre.
Flats are typically secured with a Snappi-style fastener or diaper pins when wrapped around the body.
They require a separate cover.
Prefolds
A prefold is a rectangular absorbent diaper with additional layers sewn through the centre.
It can be wrapped around the body for 360° absorbency or folded into a pad and placed inside a cover.
When wrapped, it is usually secured with a Snappi-style fastener or diaper pins.
It requires a separate cover.
Contours
A contour is an absorbent diaper that has already been cut into an hourglass or diaper-like shape.
This eliminates some of the folding required with a flat or prefold.
Traditional contours usually do not have built-in closures and may or may not have elastic.
They are normally secured with a Snappi-style fastener or diaper pins.
Because the absorbent fabric wraps around the body, contours can provide 360° absorbency.
They require a separate cover.
Fitted diapers
A fitted diaper is already shaped like a diaper and usually includes elastic and built-in closures.
The absorbency wraps around the body, but much of the folding and fastening work has already been built into the diaper.
Fitted diapers may close with snaps, hook-and-loop, or occasionally ties.
They still require a separate cover.
Separate covers
Flats, prefolds, preflats, contours, and fitted diapers provide the absorbency.
The cover provides containment.
The most common reusable choices include PUL, wool, and alpaca.
PUL covers
A standalone PUL cover is a waterproof shell worn over an absorbent diaper.
Most have elastic around the legs and waist and close with snaps or hook-and-loop.
They are generally lightweight and trim and can be worn over almost any absorbent diaper that fits underneath.
Wool covers
A properly prepared and lanolized wool cover provides a highly water-resistant outer layer.
Wool covers come in several different styles.
Some are wrap-style covers with snaps or hook-and-loop closures.
Others pull on.
Wool clothing can also do double duty as the diaper cover.
Soakers are pull-on covers.
Shorties work as both shorts and a diaper cover.
Longies work as both pants and a diaper cover.
Skirties combine clothing with the cover function as well.
This can eliminate the need for a separate pair of pants or shorts over the diaper.
The absorbency underneath does one job.
The wool clothing over top does another.
And yes, your baby's pants can actually be part of the diaper system.
Alpaca covers
Alpaca covers can also provide a natural-fibre outer layer.
Like wool, they may come in pull-on or clothing-style designs.
Unlike sheep's wool, alpaca is not treated with lanolin as part of the diapering system.
Depending on the alpaca fibre and construction, the fabric may be intentionally felted or shrunk to reach the density and performance required for a diaper cover.
Care instructions become especially important so the finished cover does not continue felting or shrinking beyond what was intended.
Which cover is best?
There isn't one answer.
Some families prefer PUL.
Some prefer wool.
Some use alpaca.
Some use PUL during the day and wool overnight.
Some use wool pants as both clothing and a diaper cover.
Some use disposables and add a natural-fibre cover when they need extra containment.
You do not have to pledge allegiance to a diaper system.
Understanding what each material does is more useful than picking a team.
The absorbency catches the moisture.
The cover contains it.
How you accomplish those two jobs is where all the options come from.
Closures and fasteners
Closures are another part of cloth diapering that sounds more complicated than it really is.
Their job is simply to hold the diaper or cover where it belongs.
Snappi-style fasteners
Snappi-style fasteners grip compatible fabric.
They are commonly used with flats, prefolds, preflats, and contours.
Not every fabric works equally well with this type of fastener, so check the recommendations for the specific diaper.
Diaper pins
Diaper pins are the traditional option.
They work with a wide range of fabrics and allow very precise adjustment.
They take a little practice, but they are mechanically very simple.
Snaps
Snaps are commonly built into fitted diapers, PUL covers, wool wrap covers, pocket diapers, AIOs, and AI2s.
They are secure and allow multiple waist and rise settings to be built into a diaper.
Hook-and-loop
Hook-and-loop is often called Velcro, although Velcro is a brand name.
It is quick and familiar.
If you have put on a disposable diaper, the basic movement feels very similar.
Hook-and-loop can be found on PUL covers, fitted diapers, pockets, AIOs, AI2s, and some wool wrap covers.
Pull-on
Not every cover needs a fastener.
Many wool and alpaca covers simply pull on.
Soakers, shorties, longies, and similar clothing-style covers rely on the stretch and shape of the garment rather than snaps or hook-and-loop.
Ties
Ties are less common but still appear on some traditional and artisan diaper styles.
They allow a customized fit without predetermined snap positions.
There are tradeoffs everywhere
That is really the theme of cloth diapering.
More sewing, elastic, closures, shaping, and built-in components can make a diaper much faster and easier to put on.
Simpler diapers usually require more folding or fastening.
Natural fibres have their own characteristics.
Synthetic materials have theirs.
Some options cost more because more fabric, hardware, construction, and labour go into making them.
Others are incredibly simple pieces of fabric that ask the caregiver to do more of the work during the diaper change.
None of that automatically makes one system good and another bad.
It just moves the work around.
The goal is not to find the diaper the internet has declared "best."
The goal is to understand what you are buying well enough to decide what works for your family.
Extra Bonus Details
Swim diapers
Swim diapers are a completely different category from regular cloth diapers.
Their job is not to absorb urine or keep water out.
A swim diaper is designed to fit snugly around the waist and legs, help contain solid stool, and allow pool or lake water to move through the diaper.
This is important for both function and safety.
A regular PUL cover, pocket diaper, all-in-one, or other absorbent diaper should not simply be substituted for a properly designed swim diaper.
If absorbency is left inside a pocket diaper or another cloth diaper, it can soak up a significant amount of water and become heavy.
Even using a waterproof cover by itself is not automatically the same as using a swim diaper. Swim diapers are specifically designed so water can move through rather than becoming trapped inside the garment.
You do not want to accidentally create a little water-filled balloon around your child.
And you definitely do not want a diaper acting like an unintended flotation device or changing how a child sits and moves in the water.
A proper swim diaper focuses on:
- A snug fit around the legs and waist
- Containing solid stool as much as possible
- Allowing water to flow through freely
- Avoiding absorbent inserts or soakers
- Staying lightweight in the water
Swim diapers are also not completely poop-proof. The CDC notes that they can help contain solid stool for a short period, but they are not leakproof and cannot prevent germs or diarrhea from entering the water.
Check swim diapers regularly and change them away from the pool or swimming area.
The simplest rule is:
Regular diapers absorb. Swim diapers contain.
Do not add absorbency to a swim diaper, and do not assume that a regular cloth diaper or waterproof cover is automatically safe for swimming.
