Water, edges and glue: what actually kills a cabinet
Almost every cabinet that dies young dies the same way, and it is never the panel that fails. Water finds a cut edge, the core drinks it, and the board swells into a shape that cannot be sanded, planed or pressed back. This page covers the three defences that matter: which board grade to specify, what the adhesive under the edge tape is doing, and which of the edges nobody ever sees are worth paying to seal.
A faced board is armoured on its faces and naked on every cut edge. Seal the edges and an ordinary chipboard cabinet lasts decades in a kitchen. Leave one bare where water collects and that cabinet has a few wet years in it. Moisture-resistant board buys margin rather than immunity, plywood tolerates damp better than chipboard without being waterproof either, and the adhesive holding the tape on decides how long the seal stays a seal. The cheapest real upgrade on this page is banding the edges you cannot see.
Water gets in at the edge, never the face
The face of a melamine-faced board is a plastic-impregnated decor layer fused under heat and pressure. Spill water on it, wipe it up an hour later, and nothing has happened. That surface is not the problem and never was.
Cut the sheet and you expose the core: wood particles held together with resin, with air between them. Wood particles absorb water and swell, and because the faces are sealed, the swelling has only one direction to go. The edge grows, the surface above it lifts and cracks, and the board takes on the crumbly, blistered look everyone recognises from under a sink. Two details make it worse than it sounds:
It is permanent. Timber that gets wet and dries returns to roughly its old shape. A swollen chipboard edge does not. The particles have been pushed apart and the resin bonds between them are broken.
It is slow and invisible. The damage happens at the bottom rear edge of a sink base, against the wall, behind a waste bin. By the time anyone sees it, the fix is a new panel.
So the whole moisture question reduces to one thing: how well are the cut edges sealed, and how long does that seal hold. Board grade is a second-order improvement on top of it.
Moisture-resistant board: what the green core means
Moisture-resistant chipboard and MDF, usually tinted green so it can be told apart on the saw, are made with a water-repellent resin system. Under the standard test the board swells substantially less in thickness after a soak than a normal grade does.
What that buys you, stated honestly:
Time. A splash that sits on an MR edge for an hour does less than the same splash on a standard edge. In a kitchen, spills get wiped and that margin is often the whole difference.
Not immunity. Nothing here is waterproof. Leave an MR edge standing in a leak for a week and it swells too. The label means resistant, and resistant is a rate, not a wall.
No excuse to skip banding. An unbanded MR edge is still an exposed core. Sealing beats grade, every time.
Where it earns its price is the short list of places that get wet repeatedly: the sink base, the cabinet next to a dishwasher, a laundry run, a bathroom vanity. Specifying MR board for a whole kitchen when three cabinets are at risk is spending in the wrong place.
Our standard carcass board is 18 mm melamine-faced chipboard. A moisture-resistant grade is not a switch in the editor; ask us and we will quote it for the cabinets that need it.
Plywood in a wet place
Plywood handles damp better than chipboard for a structural reason rather than a chemical one. It is veneer, so the wood is still in continuous sheets rather than crumbs, and the cross-grain stack means that swelling in one layer is resisted by the two next to it. A plywood edge that gets wet usually dries and carries on.
Two cautions before treating it as the answer. Cheaper grades hide voids inside, and a void that fills with water is a slow leak inside the panel. And the glue matters more than the species: interior-grade plywood delaminates when it is repeatedly soaked, while exterior and marine grades are bonded to survive it, at a price that rarely makes sense inside a kitchen.
The practical version: plywood is a sensible upgrade for a sink base or a laundry cabinet, and it still wants every cut edge sealed. Read the comparison of the three materials for what else changes when you switch, including the sheet-size catch that stops a tall pantry side from existing in one piece.
The glue under the tape
Edge tape is only as good as what holds it on, and this is the part of a quote nobody itemises. Three adhesive systems are in use, and they differ in exactly the way that matters here: how well the seam between tape and panel survives water and steam.
System
How it works
The seam
Against water
What it costs
EVA hot-melt
A thermoplastic glue melted onto the panel edge as the tape is pressed on
A visible glue line, often a slightly different colour from the tape
Weakest of the three. The glue line is the seam water and steam find first
Lowest, and it runs on every edgebander ever built
PUR (polyurethane)
A reactive adhesive that cures with moisture and cross-links, so the bond is chemical rather than a re-meltable film
A much thinner line, closer to invisible
Markedly better. It does not soften with heat and resists steam and repeated wetting
Higher glue cost, and the machine has to be set up and purged for it
Laser or hot-air (zero joint)
The tape carries its own functional layer, which is melted and fused to the panel with no separate adhesive at all
Effectively no line. The tape reads as part of the panel
Best available, because there is no third material in the joint to fail
Highest, and it needs both a machine that can do it and tape made for it
EVA hot-melt
The industry default for interior and low-exposure edges
PUR (polyurethane)
Wet rooms, steam paths, worktop-height edges and anything premium
Laser or hot-air (zero joint)
Show surfaces and the top of the market
The dark line you sometimes see between a worktop-height panel and its edge tape is EVA that has been softened by steam and picked up dirt. That line is the failure starting: once the bond opens by a fraction of a millimetre, water has a path into the core, and the tape that looks intact is no longer sealing anything.
Which of the three a given workshop runs comes down to the machine it owns, since the adhesive system is a property of the edgebander rather than something chosen per order. It is a fair question to ask any supplier, and a more useful one than the tape material, because the tape is visible on the finished panel and the glue line is what fails first.
Do the hidden edges need banding?
This is the question that decides whether a cabinet survives its plumbing, and the honest answer splits by where the edge is.
The trade standard, and our default, seals what you see: all four edges of every front, and the front edge of every carcass panel. The edges left bare are the ones facing the wall, the ones at the floor, and the ones where two cabinets meet.
Coverage
What gets taped
When to choose it
Visible
Fronts on all four edges, carcass panels on the front edge only
The industry-normal default and ours. It seals every edge you can see or touch, and leaves the hidden ones bare
All
Every exposed carcass edge as well, including the ones at the floor and against the wall
The one worth paying for in a kitchen, a bathroom or a laundry. It costs extra tape and an extra machine pass on edges nobody looks at, and it is the cheapest lifespan you can buy
None
No tape anywhere
Exists for costing a bare box. Not a build to order for a room with plumbing in it
Which of the hidden edges actually matter, ranked:
The bottom edge, every time. It is the one that meets a mopped floor, a spill that runs, or a leak that spreads before anyone notices. If you band one hidden edge in the whole kitchen, band this one. Better still, band it and stand the box on legs so it never sits in water at all, which is what the base does for you.
Anything inside a sink base. Everything in that cabinet lives under a joint that will drip one day. This is the cabinet to over-specify.
The edge against the wall, in a bathroom or a laundry, where walls carry condensation. In a dry room it matters much less.
Edges between two cabinets: lowest priority. They are pressed together, dry, and out of reach of water. Banding them is about tidiness rather than lifespan.
What sealing the hidden edges costs
Banding is billed twice, and knowing that explains the number on a quote. The tape itself is a consumable measured in linear metres, and the machine pass that applies it is a separate process charge on the same length. Going from visible to all adds metres to both lines at once.
In proportion, it stays small. The extra edges are the rear and bottom edges of carcass panels, which is a modest addition to a tally that already includes every front on four sides. Set against replacing a swollen sink base and the worktop above it, the arithmetic is not close.
Because our pricing is per part rather than per cabinet, you can see it instead of guessing: switch the coverage in the editor and the banding lines move while the boards stay the same. Use it as a costed decision rather than a leap of faith.
The wet-spot playbook
Four cabinets in a normal house take almost all the water damage. Handle them differently from the rest:
The sink base. Every edge banded, box up on legs, and a moisture-resistant board grade if you want the belt as well as the braces. Leave the back open or notched so a leak runs to the floor where you can see it rather than pooling inside.
The cabinet beside the dishwasher. Machines vent steam when the door opens on a hot cycle, and it goes sideways into the neighbour. Band that side.
Laundry and utility. Standing water on the floor is normal in these rooms rather than exceptional. Legs and full coverage are the minimum.
Bathroom vanities. Constant humidity rather than spills, so the enemy is condensation on cold surfaces and every unsealed edge in the room. This is where a wall-hung box pays for itself twice.
Everywhere else in the house, a well-banded standard board is the right call, and spending the same money on better hardware will improve your day more.
See what sealing everything costs before you decide
Switch banding coverage from visible to all and the tape metres and the machine pass both update while the boards stay the same, so the lifespan upgrade is a number rather than a leap of faith. Ask us about moisture-resistant board or plywood for the cabinets that need it.
What is moisture-resistant chipboard and is it waterproof?
It is chipboard made with a water-repellent resin system, usually tinted green so it can be identified on the saw, and it swells substantially less than a standard grade when it gets wet. It is not waterproof and nothing sold for furniture is. What it buys is time: a spill that sits on it for an hour does less damage than the same spill on a standard board. It is worth specifying for the cabinets that get wet repeatedly, such as a sink base, a dishwasher neighbour or a laundry run, and it is a poor substitute for sealing the edges, since an unbanded moisture-resistant edge is still exposed core.
Why does chipboard swell and can it be repaired?
The faces of a melamine-faced board are sealed, but every cut edge is raw core: wood particles held together with resin. Wood particles absorb water and expand, and with the faces sealed the swelling has only one way to go, so the edge grows and the surface above it lifts and cracks. It cannot be repaired. Unlike solid timber, which returns roughly to its old shape after it dries, the particles in a swollen board have been pushed apart and the resin bonds between them are broken. The damaged panel has to be replaced.
What is the difference between EVA and PUR edge banding glue?
EVA is a hot-melt thermoplastic: it is melted, pressed on and cools back to the same material, which means heat and steam can soften it again. PUR is a reactive polyurethane that cures by cross-linking, so the bond is chemical and does not re-melt. In practice PUR gives a much thinner and less visible glue line and holds up markedly better against steam and repeated wetting, which is why it is specified at worktop height and in wet rooms. It costs more, both in adhesive and in machine setup. The dark line that appears between a panel and its edge tape over a kettle or a dishwasher is usually EVA softening and collecting dirt.
What is zero-joint or laser edge banding?
A method where the tape carries its own functional layer on the back, which is melted by a laser or hot air and fused directly to the panel, with no separate adhesive in the joint at all. Because there is no third material in the seam, there is effectively no visible glue line and nothing to soften with heat or steam, which makes it the most water-resistant option available and the most expensive. It needs both a machine that can do it and tape manufactured for it, so it is a show-surface and premium-market choice rather than a default.
Do you need to edge band edges you cannot see?
Some of them, and the priority is clear. The bottom edge matters most, because it meets mopped floors, spills that run and leaks that spread before anyone notices, and it is the single most common way a cabinet dies. Everything inside a sink base is next, since it sits under a joint that will drip eventually. The edge against a wall matters in a bathroom or laundry where walls carry condensation, and much less in a dry room. Edges where two cabinets meet are the lowest priority: they are pressed together, dry, and banding them is about tidiness. Our default coverage seals what you see, and switching to full coverage adds the rest.
How much does it cost to band all the hidden edges?
Less than most people expect, because banding is billed as tape by the linear metre plus the machine pass that applies it, and full coverage only adds the rear and bottom edges of carcass panels to a tally that already includes every front on four sides. Since our pricing is per part, you can see the difference rather than estimate it: switch the coverage setting and the banding lines change while the board cost stays the same. Compared with replacing a swollen sink base and the worktop sitting on it, it is one of the cheapest upgrades available.
Is plywood better than chipboard in a bathroom or laundry?
Generally yes, for a structural reason rather than a chemical one. Plywood keeps the wood in continuous veneers rather than crumbs, and the cross-grain stack means swelling in one layer is resisted by its neighbours, so a plywood edge that gets wet usually dries and carries on. Two cautions: cheaper grades hide internal voids, and a void that fills with water is a slow leak inside the panel; and the glue matters more than the species, since interior-grade plywood delaminates under repeated soaking while exterior grades are bonded to survive it. Plywood still wants every cut edge sealed.
What is the best way to protect a sink cabinet from water?
Do four cheap things rather than one expensive one. Band every edge including the hidden ones. Stand the box on legs so it never sits in water on the floor. Leave the back open or notched, so a leak runs out where you can see it instead of pooling inside the cabinet. Consider a moisture-resistant board grade or plywood for that one cabinet rather than for the whole kitchen. Together those cost very little at the design stage, and they are the difference between a leak you mop up and a cabinet you replace.
