Most shed problems start before the first wall goes up. The base is not level, the floor frame is too light, the roof fall is guessed, or the door opening is built slightly out of square. You only discover the mistake at the end, when the door rubs, the roof feels wrong, or the shed twists after a wet winter.

This guide is not trying to give one perfect shed plan that suits every garden. A 6x8ft shed is a useful example size, but the real value is learning how to plan the timber, sheets, cladding, roof and door properly. You can scale the method up or down as long as you keep the structure sensible.

• Pent roof only
• Central door as standard
• Structural treated timber frame
• OSB3 floor and roof deck
• Shiplap, loglap, T&G or featheredge cladding
• Material planning method included

What this shed guide is designed to help with

The example build is a simple pent-roof timber shed around 6x8ft, which is roughly 1.8m x 2.4m. The front is the higher side, the back is the lower side, and the roof falls from front to back. That keeps the roof easier to frame than an apex roof and makes the whole guide easier to follow.

The standard layout uses a central door on the front. A central door is easiest to understand, easiest to frame, and works well for a general storage shed. You can move the door to one side if you want more uninterrupted wall space for racking, bikes, garden tools or a mower, but keep the opening properly framed and make sure the door still has enough clearance to swing open.

Before you worry about timber, decide where the shed is going

A shed that sits in a wet hollow will always have a harder life than a shed on a well-drained, level area. Look for somewhere firm, accessible and not constantly holding water. Also think about how you will carry sheets, longer timber and cladding to the build area before the delivery arrives.

For a practical pent-roof shed, the aim is usually simple: keep the roof high enough to be useful inside, but do not push the height so close to the limit that a sloping garden, raised base or measurement error creates a problem. Measure from the actual ground level around the building, not just from the floor frame.

Choose the base before you build the floor

The base decides whether the shed stays square. Do not sit the timber floor frame directly on soil. Even treated timber should not be left sitting in wet ground where water can constantly soak into it.

Use structural treated timber, not CLS

For this shed, use structural treated timber for the main frame. CLS is often used for internal studwork, but it is not the right product to push for an external garden shed frame in this guide. The shed needs a frame that makes sense outdoors.

For most garden shed framing, think in three areas:

• Floor frame: minimum 100x47mm / 4x2 structural treated timber, with 150x47mm / 6x2 where a stronger floor is sensible.
• Wall frames: structural treated timber sized to suit the shed height, cladding and door layout.
• Roof rafters: structural treated timber sized to suit the span, roof deck, roof covering and overhang.

Use the same thinking as a small framing job: the floor carries the load, the walls need to stay square, and the roof needs proper fall and support. Do not choose timber purely because it is the smallest size you can make fit on paper.

Sheet materials: OSB3 first, plywood where suitable

For the floor deck and roof deck, OSB3 sheets are the expected choice for this type of project. OSB3 is commonly used for shed floors, roof decks and general construction projects where a structural sheet is needed in humid conditions.

Plywood may also be suitable for some shed floors or roofs, depending on the specific sheet, thickness, exposure and protection. If you are using shuttering ply or another plywood sheet option, check the product specification before treating it as a like-for-like OSB3 replacement.

Cladding options that make sense

The outside finish can be adapted depending on the look you want and the products you prefer to use. The main options are:

You can browse the main timber cladding range, including shiplap, loglap and tongue and groove options. For featheredge-style shed cladding, see treated featheredge boards.

Material planning method

Instead of pretending one shopping list fits every shed, use this method. It helps you plan the job properly and adjust for your chosen size, board length and cladding type.

1. Floor frame timber

Start with the outside floor size. For a 6x8ft-style shed, that might be around 1.8m x 2.4m. Plan two long rim joists, two end joists, and internal joists at sensible centres. For a shed floor, closer joist spacing gives a firmer feel, especially if you are storing heavy garden tools.

Use at least 100x47mm / 4x2 structural treated timber for the floor. If you are storing heavier items or want a stiffer floor, step up to 150x47mm / 6x2.

2. Wall frame timber

Draw each wall as a rectangle before you cut. Mark the bottom plate, top plate, corner studs, intermediate studs and door opening. For the front wall, mark the door first, then work out the studs either side. This is easier than building a full wall and trying to cut the opening afterwards.

For a central door, keep enough timber either side of the opening so the front wall is not weak. If moving the door to one side, keep the hinge side well supported and leave enough frame around the latch side.

3. Roof timber

A pent roof needs a clear high side, low side and fall direction. In this guide, the roof falls from the front down to the back. Plan enough rafters to support the OSB3 roof deck and allow a modest overhang to help throw water away from the walls.

The higher you make the shed, the more carefully you need to check the planning height and boundary position. Do not just add height because it feels useful inside.

4. Sheet materials

Most sheet materials are planned around 2440mm x 1220mm sheet sizes. For a 2.4m x 1.8m-style shed floor, think about where each sheet joint will land. If a joint falls between joists, add support. Do the same on the roof deck.

As a rule, do not leave sheet joints unsupported and do not rely on a roof covering to hide a weak roof deck.

5. Cladding

Do not calculate cladding from the total board width alone. Calculate from the effective coverage once the overlap or tongue-and-groove profile is installed. Measure the wall area, subtract the door opening if useful, then divide by the effective board coverage. Add sensible waste for cuts, mistakes and awkward ends.

6. Fixings and hardware

You will need framing screws, sheet screws or nails, cladding nails, roofing felt fixings, hinges, latch hardware, and possibly fascia or trims. Browse timber fixings, nails and ironmongery before you start so the build does not stop halfway through for missing basics.

Example cut planning for a 6x8ft-style shed

This is not a fixed shopping list. It is a planning example to help you understand the frame before adapting it to your chosen size.

Step-by-step build method

Step 1: Set out the base

Mark the shed footprint using pegs, string or spray marker. Check the diagonals to make sure the shape is square. Prepare your chosen base: slabs, blocks on compacted gravel, or treated bearers/skids supported off wet ground.

Take your time here. A few millimetres of twist in the base can become a door problem later.

Step 2: Build the floor frame

Cut the floor perimeter from structural treated timber. For a good shed, use 100x47mm / 4x2 as the minimum starting point. Step up to 150x47mm / 6x2 if the shed is carrying more weight, spanning between fewer supports, or you simply want a stiffer floor.

1. Lay out the perimeter timbers on the base.
2. Fix the corners square.
3. Add internal joists at sensible centres.
4. Check diagonals before fully tightening everything.
5. Set the frame onto the base and check that it does not rock.

Step 3: Fit the floor sheets

Lay the OSB3 sheets over the floor frame and plan the joints before fixing. Sheet edges should land on joists or added noggins. Leave a small expansion gap where needed and avoid forcing sheets tightly together.

Mark joist lines on the top face of the sheet before fixing. This helps you drive screws into timber rather than guessing through the board.

Step 4: Frame the back wall

The back wall is the low side of the pent roof. Build it flat on the shed floor if possible. Use a bottom plate, top plate, corner studs and intermediate studs. Keep the frame square before standing it up.

Brace the wall temporarily once raised. Do not leave freestanding wall frames unsupported in wind.

Step 5: Frame the front wall with the central door

The front wall is the high side of the pent roof. Mark the central door opening first. Then add door studs, corner studs, intermediate studs and a header above the door.

The door opening should be square, not just the right width. Check the diagonals of the opening if needed. A shed door is far easier to hang when the opening is right from the start.

If you want to move the door to one side, do it on the drawing before you cut timber. Offset doors can make the inside more useful because one wall becomes better for shelves or long tools, but the door side still needs proper framing and enough fixing strength for the hinges.

Step 6: Build the side walls to suit the roof fall

The side walls connect the higher front wall to the lower back wall. That means the top of each side wall follows the roof slope. Do not guess this angle early. Confirm your front and back wall heights, then mark the slope accurately.

For a confident beginner, the cleanest method is to build the side wall frame carefully rather than trying to hide rough cuts later. Mark the top line, cut neatly, and keep checking that the frame sits flat and square.

Step 7: Tie the wall frames together

Stand the walls, check plumb, and fix the corners together. Fix the bottom plates down into the floor frame. Use temporary braces while you work. The shed should now feel like one box rather than four separate panels.

Before fitting the roof, check:

• The front wall is straight.
• The back wall is straight.
• The corners are pulled together properly.
• The door opening is still square.
• The roof fall runs the correct way.

Step 8: Fit the pent roof rafters

Run the rafters from the high front wall to the low back wall. Allow a sensible overhang to help throw water away from the cladding. Space the rafters so the roof deck is supported and sheet joints can land properly.

Once the rafters are in place, sight across them. Twisted or uneven rafters make the OSB3 roof deck harder to fix and can leave the felt sitting badly.

Step 9: Deck and cover the roof

Fit OSB3 sheets to the rafters, keeping joints supported. Once the roof deck is fixed, cover it promptly. Do not build the roof deck and leave it exposed to rain.

For a simple shed, use shed felt or a suitable roofing membrane following the product instructions. Work with the roof fall, overlap correctly, and make sure the edges are detailed so water does not run back into the timber.

Step 10: Clad the walls

Fit the cladding after the shed frame is square and the roof is protected. Work from the bottom up where the profile requires it. Keep boards level, fix into studs, and check the product orientation so water sheds correctly.

For shiplap, loglap or tongue and groove, use the effective coverage of the board when planning quantities. For featheredge, allow for the overlap. Treat cut ends where needed and avoid leaving exposed cuts unprotected.

Step 11: Build and hang the door

Build the door to the finished opening, not just the drawing. A simple framed ledge-and-brace door works well for this shed. The door needs solid fixing points for hinges and enough clearance to move without rubbing.

Brace direction matters. The diagonal brace should support the latch side back towards the hinge side so the door resists sagging. Fit the hinges into solid timber, pack the door evenly in the opening, and test swing before final fixing.

Step 12: Add trims, fascia and final protection

Finish the corners, roof edges and exposed cuts. Fascia and trims are not just cosmetic; they help cover vulnerable edges and make the shed look intentional rather than unfinished.

Once the shed is built, apply a suitable exterior treatment or paint system as required by the products used. Pay attention to cut ends, lower boards, door edges and anywhere water could sit.

Before you order checklist

Useful Wern-Wood categories for this build

Common mistakes that make sheds fail early

• Using too-light timber for the floor: the floor feels weak and the shed twists more easily.
• Building directly on soil: timber stays wet and the base moves.
• Guessing the roof fall: water does not clear properly and roof edges become vulnerable.
• Unsupported sheet joints: OSB3 edges flex, lift or weaken.
• Forgetting the door until the end: the opening is slightly out of square and the door becomes a fight.
• Calculating cladding from total board width: you run short because overlap and profile coverage were ignored.
• Skipping cut-end protection: the most exposed areas are often the weakest points.

FAQs

Final thought: build the shed around the weak points

A shed is not complicated, but it is unforgiving if the basics are rushed. Get the base level, make the floor strong, use structural treated timber, keep the frame square, support the OSB3 properly, and plan the roof fall before you start cutting. That is what makes a garden shed feel solid rather than temporary.

Start with the frame and sheet materials, then choose the cladding and roof covering that suits the finish you want.

General guidance only. Always check product specifications, manufacturer instructions, ground conditions, local planning restrictions and safe working practices before building. For unusual sites, heavy loads, electrical work, habitable conversions or boundary-sensitive projects, seek competent advice before starting.