Buying Guides · 6 min read
Tongue and Groove vs Overlap Cladding: Which Shed Lasts?
Overlap or tongue and groove for your shed? A craftsman's straight answer on what each cladding does in British weather — and what to ask before buying.
Cladding, plainly
The wall is the shed: overlap vs tongue-and-groove
Two sheds can look identical in a photo and behave completely differently in February. The difference is how each board meets the next — the single most useful thing to understand before you buy.
Take away the roof and the floor and a shed is mostly one thing: wall — and a timber wall is only as good as the joint between one board and the next. That joint, a simple overlap or a machined interlock, decides whether wind-driven rain stays outside or ends up on your mower, your bikes and your tools.
We've machined cladding in our own West Midlands workshop since 1995, so we'll declare our hand up front: every timber building we make is clad in shiplap tongue-and-groove. But overlap has a legitimate place too, and this guide is honest about where. If you're weighing up a first shed, our buying guide is a good companion to this one.
The three profiles, plainly
Overlap (feather-edge)
Overlap is the budget option, and it doesn't pretend otherwise. Sawn boards — usually tapered feather-edge — are nailed on horizontally, each lapping the board below like tiles on a roof. It's the cheapest way to clad a shed, and the rough-sawn look has a rustic charm of its own.
The trouble is what happens next. The boards are thin and only held where the nails go. As the timber dries and shrinks, gaps open between the laps; wind-driven rain and draughts work in behind them; boards cup, twist and spring loose. And the rough sawn surface drinks paint unevenly, so it never quite holds a finish.
Tongue-and-groove
Tongue-and-groove is machined, not just sawn. Each board carries a tongue along one edge and a groove along the other; the tongue locks into the groove of its neighbour. The result isn't a stack of separate boards but one interlocked wall: water sheds at every joint, there's no straight-through gap for wind to exploit, and when the timber moves with the seasons the joint stays closed.
There's a structural bonus too: an interlocked panel resists racking — that parallelogram lean a flimsy shed develops every time the door is pushed. And the smooth machined face takes stain or paint properly.
Shiplap — tongue-and-groove, refined
Shiplap is tongue-and-groove with one more idea machined into it: a scooped channel across the face of each board that catches rainwater and steers it down and off the wall instead of letting it sit on the joint below. It's the profile on every timber building we make, machined from tanalised, pressure-treated timber so the protection runs right through the board.
So which should you buy? The honest answer
Overlap is fine if…
- You need a short-life store for low-value kit and price matters most
- The building sits somewhere sheltered, out of driving wind and rain
- You're happy re-nailing boards as they cup and work loose
- A rustic, rough-sawn look suits the corner it lives in
- You'd rather spend less now than still own it in ten years
Choose interlocked cladding if…
- The contents matter — tools, bikes, anything electrical or upholstered
- You want the building to last decades, not seasons
- The site catches weather: open gardens, hilltops, sideways rain
- You plan to stain or paint it and want the finish to hold
- You'd rather buy once than buy twice
What an interlocked wall buys you
Sheds rain by design
Every joint is a lock, not a lap: water runs down the face and off, instead of finding a gap to sit in.
No through-gaps
No straight path from outside to inside, so draughts can't whistle through every time the wind gets up.
A stiffer building
Interlocked boards brace each other against racking, so doors keep closing squarely years after a nailed-on wall would have leaned.
A finish that holds
The machined face takes stain or paint evenly, and boards that stay put don't crack the film the way cupping overlap does.
Quieter in wind
No loose edges to rattle and drum on a rough night. A locked wall simply has nothing to flap.
Profile is half the story
Here's the part most listings gloss over: a tongue-and-groove badge on a thin board is still a thin wall. Thickness matters as much as profile — flimsy T&G flexes, and flex is what opens joints. Always ask for the finished thickness, after machining, not the flattering nominal figure.
Then ask what's behind the cladding, because boards are only as solid as the framing they're fixed to. A well-machined skin on spindly framing is a suit on a scarecrow. Our Standard vs Heavy Duty vs Composite comparison lays our framing and cladding specifications out side by side — exactly what sits behind the wall you're paying for.
And a proper wall is a build-up, not a single layer. Every building we make carries a breathable membrane within the wall construction — letting moisture vapour escape from inside while keeping wind-blown water out, so the timber stays dry from both directions. To see a full specification on your own footprint, the Build Studio lets you configure a building panel by panel.
Cladding questions, answered straight
Are overlap sheds waterproof?
When new and in a sheltered spot, mostly. But an overlap wall relies on gravity and the lap alone — no joint holds the boards together. As they dry and shrink, gaps open and wind-driven rain gets in behind. Fine for a short-life store of kit that can take the odd damp day; not for anything you'd mind getting wet.
What thickness should shed cladding be?
Budget overlap is often only 7–8mm of sawn board; decent tongue-and-groove starts around 12mm finished — and finished is the figure to ask for, since nominal sizes are quoted before machining. The framing behind the boards matters just as much, so ask about both together.
What is shiplap cladding exactly?
Shiplap is tongue-and-groove with a scooped profile machined across the face of each board. You get the interlock — tongue locked into groove, no through-gaps, a stiff panel — plus a channel that steers rainwater down the face of the wall and away from the joints. It's what we build with on every timber building, machined from tanalised timber.
Can you paint an overlap shed?
You can, but it's thankless. The rough-sawn surface drinks paint unevenly, and because the boards cup and move independently, the film cracks along every lap within a season or two. Machined tongue-and-groove takes stain or paint evenly and holds it — the surface is smooth and the boards stay put.
Why are overlap sheds so cheap?
Because everything about them is cheaper to make: thin sawn boards instead of thicker machined ones, no tongues or grooves to cut, quick nailing instead of jointing. Nothing dishonest in that — the problem starts when a short-life building is sold as a long-life one. If you want decades from a shed, interlocked cladding is the floor, not a luxury.
Cladding questions to ask any shed seller
Keep these on your phone. A maker who knows their product will answer all seven without blinking — hesitation is an answer too.
- Is the cladding overlap or interlocked tongue-and-groove?
- What's the finished board thickness — after machining, not nominal?
- Is the timber pressure-treated (tanalised) or just dip-treated?
- What size is the wall framing behind the cladding?
- Is there a breathable membrane in the wall build-up?
- How stiff is the panel — will the wall resist racking over time?
- Will the surface take stain or paint, and how long will it hold?
Tanalised shiplap on every timber building we make
We've machined interlocked cladding in the same family workshop since 1995 — FSC-certified timber, pressure-treated right through, free delivery across mainland UK. Browse the range, or start from your own footprint in the Build Studio.
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