Autumn is the best time of year to look after a timber shed. The weather is still mild enough for treatment to dry properly, and you have a few weeks before the cold, wet months arrive.
Leave it until December, and you are working in the rain on wood that is already damp. Treatment will not soak in, and any small problem you missed will have grown.
This guide walks through a simple autumn routine, tells you what to check, and explains how to spot the point where repairs stop being worth the money.
Why shed treatment matters
Timber is a natural material. Left bare, it takes in water, dries out, swells, shrinks and eventually rots. Wood-boring insects are drawn to damp timber too.
A coat of preserver or paint puts a barrier between the wood and the weather. It is not a one-off job. The barrier wears away in sunlight and rain, so it needs topping up every few years.
All our sheds leave the workshop with one coat of oil-based wood stain, in your choice of eight colours. That first coat gets the building started. Keeping it going is the owner’s job, and it is not a hard one.
Start with a proper check
Before you open a tin, walk around the building and look closely. Ten minutes now saves a wasted afternoon later.
Check for:
- Soft or spongy timber, especially low down near the base
- Green algae or black mould on the shady side
- Gaps opening up between cladding boards
- Nails or screws that have worked loose
- Felt that is torn, lifting at the edges or holding puddles
- Doors that stick, drop, or no longer meet the frame
- Windows with cracked putty, failed sealant or misted glass
- Plants, fence panels or bins pressed up against the walls
Anything soft under a screwdriver tip is rot, not dirt. Note where it is and how much there is, because that becomes important later on.
The autumn routine, step by step
1. Clear the ground. Cut back anything growing against the shed and leave at least a hand’s width of air all the way round. Plants trap moisture against timber and stop it drying out.
2. Clean the walls. A stiff brush and warm soapy water will shift most algae and dirt. Rinse and let the timber dry fully. If you use a pressure washer, keep it on a low setting and hold it well back, because a strong jet will tear soft fibres out of the wood.
3. Clear the roof. Sweep off leaves and moss. Wet leaf litter sitting on felt is one of the most common causes of a leaking roof.
4. Fix before you treat. Tighten loose fixings, replace split boards and patch any small tears in the felt. Treating over a fault just hides it.
5. Treat the timber. Pick a dry spell with two clear days ahead. Work from the top down, using a brush to push the product into the joints and end grain, which is where water gets in first. End grain drinks far more than a flat face, so give it extra.
6. Do not forget the inside of the door edges and the bottom rail. They are the parts people skip and the parts that fail first.
How often should each job be done?
| Job | How often | Why it matters |
|---|---|---|
| Recoat with oil-based wood preserver | Every 2 to 3 years | Keeps rot and wood-boring insects out |
| Recoat with Farrow & Ball exterior eggshell | Up to every 6 years | Longer-lasting colour, resists flaking and fading |
| Sweep the roof | Twice a year, autumn and spring | Stops leaves holding water on the felt |
| Check and reseal windows | Yearly | Failed sealant lets water into the frame |
| Oil hinges, locks and catches | Yearly | Stops seizing and sagging doors |
| Cut back plants around the base | Yearly | Lets air move and timber dry |
| Check the base is level and dry | Yearly | A sinking base twists the whole building |
| Inspect felt for tears and lifting | Twice a year | A small tear becomes a soaked floor |
Weatherproofing the weak spots
Most sheds do not fail across the middle of a wall. They fail at the edges.
The roof. Felt has a working life of roughly ten to fifteen years, less if it has been sitting under a tree. Look for cracking, bald patches where the mineral coating has gone, and any lifting along the edges. Re-felting is a job worth doing properly, because everything below depends on it.
The base. Your shed should sit on a level, dry base with air able to move underneath. Slab and bearer, a concrete base and ground screws all work. What does not work is timber sitting directly on wet soil.
Doors and windows. These take the most punishment. Rain runs down the glass and sits in the frame, and every open and close puts strain on the joints. If the timber is sound but the door or window has had it, you do not need a whole new building. We make replacement doors and windows to measure in Scandinavian redwood, with finger-jointed laminated stiles that resist warping and twisting, and proper morticed and tenoned joints rather than dowels.
The cladding. Our standard is ex 19mm x 125mm shiplap, with 22mm x 175mm tanalised feather edge on heavy-duty builds. Thicker boards hold up better and hold treatment better. You can read the full detail on our cladding page.
The Royal Horticultural Society makes the same point about timing in its October garden structures advice, which recommends sorting out shed roofs and wooden repairs before winter rather than after.
When maintenance is not worth it
There comes a point where you are spending money to slow down something that has already happened. Here are the signs.
- Rot in the frame, not just the cladding. Push a screwdriver into the corner posts and the bottom rail. If it sinks in, the structure is going. Cladding can be replaced. A rotten frame cannot be saved cheaply.
- The floor gives underfoot. Soft or bouncy boards mean water has been sitting underneath, often for years.
- The building is out of square. Doors that will not shut, gaps that open at the corners, a roof line that dips. That is usually a failed base or a twisted frame.
- You are patching the roof every year. Felt that needs another repair each autumn has reached the end.
- Treatment will not soak in any more. Very old, grey, fibrous timber stops taking product. You are painting the surface and nothing else.
- You have treated it twice, and the rot came back. Rot returning in the same spot means water is still getting in somewhere you have not found.
- Repairs are creeping past a third of replacement cost. New roof, new floor, new doors, new cladding. Add it up before you commit.
If two or three of those apply, a replacement will cost less over the next ten years than keeping the old one upright.
The low maintenance route
If the reason you are reading this is that you are tired of repainting a shed every couple of years, there is a way out.
Alongside timber, we offer composite cladding options that do not need treating at all.
CanExel Ridgewood is engineered wood cladding made from wood fibre. It comes in fifteen colours, carries a twenty-five-year warranty and resists fading and warping. Because it never needs repainting, you save decades of solvent, brushes and lost weekends, and the building lasts far longer before anything needs replacing.
Durasid is a PVC composite in eighteen colours, including solid, wood effect and brushed finishes. It resists rot, moisture and insect damage and needs virtually no maintenance beyond an occasional wash.
Both sit on the same timber frame we have always used. You get the building you want, without the treatment routine.
Not sure whether to repair or replace?
Send us a few photos of your shed, along with your postcode, and tell us what is going wrong. We will give you an honest answer about whether it is worth saving.
If the answer is a new building, we will tell you what will fit, what it will cost and how long it takes. If the answer is a new set of doors and a re felt, we will tell you that too.
We have been making timber garden buildings in Danbury, Essex since 1951. We would rather point you to the right job than sell you the wrong one.