Check structural stability and electrical safety first
Do not climb onto weak roofs or work around wet electrics. Stop if floors, walls or roof timbers are soft, sagging or unstable.
MOST LIKELY CAUSES
Start with water paths, timber condition and the base
Ground settlement
Soil beneath the base has compacted unevenly.
Poor support spacing
Bearers or slabs do not support the floor evenly.
Water erosion
Drainage has washed out support material.
Inadequate original base
The platform was never level or rigid enough.
Symptom variations Match the leak, movement or moisture pattern. ⌄
- Door or window no longer aligns
- Floor slopes
- Shed walls lean
- Gaps open at corners
- One side sinks after rain
Quick checks Safe checks before dismantling the shed. ⌄
- Use a long level across the floor.
- Inspect every support point.
- Check for soft or washed-out ground.
- Measure frame diagonals.
- Look for structural cracking or rot.
Important:
Fix the water source or structural movement before replacing damaged timber or finishes.
Step 1 — Identify the low and unstable areas Make the smallest safe correction and retest. ⌄
Do not level only by adjusting the door.
Step 2 — Stabilise the ground and supports Make the smallest safe correction and retest. ⌄
Correct drainage and add proper support.
Step 3 — Lift and pack carefully Make the smallest safe correction and retest. ⌄
Raise the shed gradually using durable load-bearing materials.
Why the problem happens How moisture, movement and weather affect outbuildings. ⌄
A lightweight shed follows the shape of its base. Uneven support twists the entire structure.
Advanced checks Further diagnosis for persistent shed faults. ⌄
- Check bearer spacing.
- Assess slab thickness.
- Inspect anchoring.
- Review drainage falls.
- Check floor joist condition.
Tools and information needed Useful items for accurate checks. ⌄
- Long spirit level
- Jack rated for load
- Timber blocks
- Tape measure
- Spade
Parts or improvements that may help Common materials linked to this problem. ⌄
- Concrete slabs
- Treated bearers
- Composite packers
- Gravel sub-base
- Anchors
When to call a professional Conditions that should end basic DIY diagnosis. ⌄
- The shed is large or occupied.
- Significant lifting is required.
- The structure is rotten.
- The ground is unstable.
- Utilities run beneath the shed.
Frequently asked questions Common shed and outbuilding questions. ⌄
Can I use random timber offcuts as packers?
No. Use durable, stable load-bearing materials.
Will levelling fix the door?
Often yes if base twist caused the misalignment.
Why did it sink after rain?
Water may have softened or washed out the supporting ground.