Garden Shed Buying Guide: Size, Base, Materials and What Lasts

Buy a garden shed by the size you will need in 5 years, not the size you need today: measure your largest item, add 2 ft (61 cm) of working space around it, and buy one size up from that number, because a shed that fits today is a shed you cannot move in by next spring. Size the pad with the Concrete Calculator, measure the plot with the Square Footage Calculator, compare groundwork costs in the patio cost guide, and read the garage organization guide for the zoning system that keeps a shed usable once it is full.

Size: measure the largest item, then go one size up

Size a shed from the largest thing it must hold, because sheds are bought for mowers and bikes and filled with everything else. A standard walk-behind mower needs a door at least 36 in (91 cm) wide and a floor area of about 3 × 5 ft; a riding mower needs a door at least 48 in (122 cm) wide and a floor area of about 5 × 7 ft, plus 2 ft (61 cm) of working space on at least one side to get on and off it. Bicycles need 6 ft of length each if hung vertically or 2 ft of wall width each on a hook, and a full set of garden tools, a wheelbarrow and seasonal storage realistically needs 8 × 10 ft (80 sq ft) as a minimum for a typical suburban garden. The most common shed regret is buying 6 × 8 ft when 8 × 10 ft was needed: the price difference is typically $300 to $800, while the cost of replacing an undersized shed is the full price again plus disposal.

Check height as well as footprint: a shed with 6 ft walls and a low roof may not fit a tall ladder, a kayak on edge, or a potting bench with hanging tools, so check the interior wall height (not just the peak height) against your tallest item. Standard shed wall heights are 6 ft to 6 ft 6 in (1.8 to 2 m); if you store anything over 6 ft tall, look for a barn-style or tall-wall model. Also check the door height and width against the largest item before ordering — a shed with a 5 ft tall door will not admit a 6 ft ladder, and widening a shed door after assembly means cutting a wall panel and rebuilding the frame, which is a half-day job that a 10-minute measurement prevents.

Base: the shed is only as good as what it stands on

Build the base before the shed arrives, because a shed on uneven or soft ground twists, doors stop closing, and the floor rots from below within 3 to 5 years. The three sound options are a concrete slab (4 in or 10 cm thick, $500 to $1,500 for an 8 × 10 ft shed depending on access and labor), a compacted gravel pad (4 to 6 in or 10 to 15 cm of compacted crushed stone over landscape fabric, $200 to $600 DIY), or a timber or plastic grid base on levelled ground ($150 to $400). A concrete slab is the most durable and the best for heavy items like a riding mower, a gravel pad drains best and is the cheapest sound option, and a grid base is the fastest but only suits light storage on already-level ground. Never set a shed directly on soil or grass: ground moisture wicks into the floor, and a shed floor on soil typically rots within 3 years even on a treated frame.

Level the base to within 1/4 in (6 mm) across the whole footprint, because a shed frame racked by 1/2 in over 8 ft will show as doors that do not latch and a roof that does not sit square, and those problems get worse as the shed settles. Slope the ground away from the base so water does not pond against the walls — a shed with water standing against one wall rots that wall first, usually within 5 years. Leave 2 ft (61 cm) of clear space around the shed for maintenance and airflow, and do not plant shrubs against the walls: plants trap moisture against cladding and hide the rot until the wall is soft. If the site is not level, build a retaining edge or a raised timber frame for the base rather than digging one side down, since a dug-in base collects water.

Materials: wood, metal and plastic compared honestly

Choose the material by maintenance tolerance, not by showroom looks, because the three materials fail differently. Wood sheds ($800 to $3,000 for 8 × 10 ft) look best and are easiest to modify — shelves, hooks and windows screw straight into the frame — but they need treatment every 2 to 3 years (a $50 to $100 materials cost and a weekend) and a wood shed left untreated for 5 years will have rot at the base and around the door frame. Metal sheds ($400 to $1,500) are cheapest and need almost no maintenance, but they sweat: condensation forms on the inside of the roof and walls in temperature swings, dripping onto tools and causing rust, unless the shed is ventilated and tools are kept off the floor. They are also the hardest to modify and the noisiest in rain and wind. Plastic (resin) sheds ($600 to $2,500) need no treatment, do not rust or rot, and assemble fastest, but they cannot support heavy wall-mounted storage (shelves must be freestanding or on a frame), and cheaper models fade and become brittle in strong sun after 8 to 10 years.

Whichever material you choose, check these details before buying: a floor included or not (many metal and plastic sheds sell the floor separately, $100 to $300, and a shed without a floor is a shed on dirt), ventilation (at least two vents, high on opposite walls, to control condensation), a door that latches firmly and can take a padlock, and a roof with an overhang of at least 4 in (10 cm) so rain drips clear of the walls. For wood sheds, check that the cladding is tongue-and-groove or shiplap at least 12 mm thick, not overlap boarding under 10 mm, which warps and gaps within 2 years. For metal sheds, check the steel gauge — 0.3 mm walls dent if leaned on, while 0.5 mm or thicker resists normal use. A shed that passes these checks will last 15 to 25 years (wood, maintained), 15 to 20 years (metal) or 10 to 20 years (plastic); a shed that fails them will disappoint within 3.

Assembly, security and making it last

Budget a full day for assembly with two people, because a shed that is rushed goes up out of square and stays out of square. Assemble on a calm day — a 8 × 10 ft wall panel in a 20 mph wind is a sail, not a wall — and check the frame is square by measuring diagonals (both diagonals equal within 1/4 in or 6 mm) before fixing the roof, since a roof fixed to a racked frame locks the error in permanently. Anchor the shed to its base: ground anchors ($20 to $40 for a set) or bolts into a concrete slab prevent a light metal or plastic shed from shifting or lifting in a storm, and an unanchored shed in a 60 mph gust can move several feet or flip. Treat a wood shed the day it is assembled, not "when you get around to it" — the first treatment before the first rain is what protects the end grain and joints that rot first.

Secure the shed like the outbuilding it is: a hasp and padlock ($15 to $30) beats the latch most sheds ship with, which can be forced with a screwdriver in seconds, and a battery motion light over the door ($20 to $40) deters opportunistic theft far better than a bigger lock, since thieves prefer a dark shed to a lit one. Do not store fuel in the shed beside the mower if you can avoid it — a separate small metal fuel store or a detached fuel cabinet is safer, and many insurers require it. Keep the interior organized from day one with wall hooks for tools, a freestanding shelf unit for boxes, and the floor kept clear except for wheeled items, because a shed whose floor is covered in boxes is a shed where the mower cannot get out, which is when the shed stops being used and starts being a storage unit you pay to ignore.

Cost, permits and the final checklist

Total cost for a typical 8 × 10 ft shed is $1,000 to $4,000 all-in: shed $400 to $3,000 depending on material, base $200 to $1,500, delivery $0 to $200 (many suppliers deliver free within a radius), and treatment or accessories $100 to $300. Check local rules before ordering: many municipalities allow sheds under 100 to 200 sq ft without a permit but require a setback of 3 to 10 ft from property lines, and HOAs often restrict shed size, color and placement — a shed that violates a setback is a shed that must move, and moving an assembled shed costs $500 to $1,500. Call 811 (US) before digging any base or anchor holes to mark underground utilities, a free service that prevents a gas or electric strike.

Run the final checklist before first use: base level within 1/4 in, shed anchored, doors latch and lock, vents open, roof overhang clears the walls, wood treated, fuel stored separately, and 2 ft of clear space around all sides. A shed that passes that checklist and is one size bigger than you thought you needed is a shed that will still be useful in 10 years, when the garden has grown, the tools have multiplied, and the children have added bikes, kayaks and sports gear that the 6 × 8 ft shed you almost bought could never have held.