Decking is the surface a pressure washer is most likely to ruin. Softwood, hardwood and composite all mark if you treat them like concrete. The machine you can buy in the UK right now for most timber decks is a mains Kärcher K4 Power Control Flex Home: 130 bar you can turn down, an 8 m Flex hose, a T 5 you can raise, and room in the box for wood cleaner.
The dirt blaster stays on the hook. A close rotary jet raises the grain, stripes the boards and leaves a fuzzy deck that then holds more algae. Wide Vario, with the grain, further back than you think. If you use the T 5, put the jets on the higher setting and keep the brim moving.
This is not a lab test. Specs come from Kärcher. Street prices come from Screwfix, ITS, Trafalgar, Wickes and comparison sites on 17 August 2026. First-use distance and frost drain-down sit on how to use a pressure washer. The head itself is on the Kärcher patio cleaner page.
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If the deck is a small balcony and you already own a working K4 or K5, buy the T 5 and a bottle of wood cleaner. Do not buy another washer. If there is no outdoor socket, start with the cordless guide. A battery gun can rinse furniture. It is a poor way to strip a green 4 × 5 m deck.
Quick picks
Best overall
K4 Power Control Flex Home
From about £210
130 bar, 8 m Flex hose, T 5 in the box. The kit if you need the washer and a timber-safe head.
Best if you already have a head
K4 Power Control Flex
£199.99 at Screwfix
Same pump, no T 5. Buy the bare Flex if the head is already in the shed.
Best head for timber
Kärcher T 5
From about £55
Height-adjustable jets. Use the higher setting on wood. Keep it moving.
Best detergent
Kärcher 3-in-1 wood cleaner
£8.99 at Trafalgar
1 L Plug ‘n’ Clean bottle for treated and untreated outdoor timber. Soap does more than extra bar.
Comparison table
| Model | What it is | Why it is on this page | Typical UK price (17 Aug 2026) |
|---|---|---|---|
| K4 Power Control Flex Home | 130 bar washer + T 5 | Default deck kit. Turn the Vario down. Raise the head. | PriceSpy from £209.99. Amazon listing live, UK buy-box not locked. Viking shows ex-VAT figures |
| K4 Power Control Flex | 130 bar washer, 8 m Flex | Same pump if you already own a T 5 | Screwfix £199.99 |
| T 5 (2.644-084.0) | Clip-on head | Higher jet setting for timber. Even coverage, less striping | Trafalgar £55. Screwfix £58.99. Wickes £79 list |
| 3-in-1 wood cleaner (6.295-757.0) | 1 L detergent | Green film and tannin stains. Low-pressure apply, then rinse | Trafalgar £8.99. Official page live, no list price captured |
Prices checked 17 August 2026. A K5 will wash a deck if you turn it down. Buy one for a long drive, not because timber “needs 145”.
Kärcher K4 Power Control Flex Home
The best pressure washer for decking if you do not already own a mains washer
- Buy: Amazon Home listing (UK buy-box not locked this check; PriceSpy from £209.99) · Viking Direct £219.99 excluding VAT on a 2+ deal, £229.99 excluding VAT for one · Kärcher UK Home
- Part number: 1.324-304.0
- Pressure / flow: 20 to 130 bar, 420 L/h
- Hose: 8 m PremiumFlex
- In the box: K4, G 160 Q Power Control gun, Vario, dirt blaster, T 5, 1 L stone and façade cleaner
- Who it is for: households that need a washer and a hooded head, and will treat the deck as a low-pressure job
Home means a T 5 in the carton, not a different pump. Same 130 bar as the bare Flex. The LED on the gun shows the step. Drop it for timber and composite. Open it only if you later do stone. The stone cleaner in the box is for slabs. Buy wood cleaner for the deck. Do not then add a second T 5.
Eight metres of Flex hose covers a typical UK deck if you park the trolley at a corner. It is not enough to stand still on a long side return. The dirt blaster in the box is for stubborn spots on stone, not for the boards. Leave it on the hook.
A separate T 5 is from about £55. If the bare Flex is £200 and the head is £55, a Home box at about £210 to £245 is a small premium. A Home box at £280 is a luxury. Shop the contents list. Car & Home adds foam and car kit. Useful if those extras are cheap in the bundle. Easy to overpay when the banner just says Home.
Washer-only notes sit on the cars page and the Kärcher hub. If the deck shares a Saturday with a long, green drive, read K4 vs K5 and buy the K5 kit instead. The extra flow is for the stone, not the timber.
Skip it if you already own a working K4 or K5. Buy the T 5 and the wood cleaner. Skip it if the boards are already rotten. A washer will find the soft spots. That is not a reason to use one.
Kärcher K4 Power Control Flex
The bare machine if the T 5 is already in the shed
- Buy: Screwfix £199.99 · Amazon listing · Kärcher UK
- Pressure / flow: 20 to 130 bar, 420 L/h
- Hose: 8 m PremiumFlex
- Who it is for: anyone who already owns a T 5, or who will only use the Vario on a small deck
Same pump, same gun, no head. Buy this SKU if a Home box would give you a second T 5 you will not use. On timber the Vario is the safe default: wide fan, with the grain, keep moving. Start further back than you think and only close in if a test patch stays honest.
A K2 will rinse a table. It is a poor deck machine. Short hose, air-cooled motor, 110 bar you cannot always turn down as cleanly. That comparison is K2 vs K4.
Skip it if you need the head as well. The Home kit is then the rational box.
Kärcher T 5 T-Racer
The head that makes a deck less stripy, if you already own a K-series washer
- Buy: Kärcher Centre Trafalgar £55 · Screwfix £58.99 · Wickes £79 list this check · Kärcher UK
- Part number: 2.644-084.0
- Compatible with: K2 to K7
- Who it is for: K-series owners who want even coverage on boards without waving a lance
The height adjustment is why this head is on a decking page. Hard stone wants the closer setting. Timber and painted wood want the higher one. Kärcher claims it cleans in about half the time of a spray lance. That is a manufacturer figure, not a timed test on this site. What you can see from the design is even coverage and less striping than a wand held too close.
Keep the brim flat and moving. Park it in one spot and you will raise a ring of grain. Do not chase silvered boards until they are raw. You are lifting film, not planing the deck. The T 7 Plus also has height adjustment and a corner jet. It is K4 to K7 only and it is overkill for most timber. Head prices sit on the patio cleaner page.
Skip it if you do not own a Kärcher. Skip it if a Home kit is already in the basket.
Kärcher 3-in-1 wood cleaner
The bottle that does more for green film than another 20 bar
- Buy: Kärcher Centre Trafalgar £8.99 · Kärcher UK
- Part number: 6.295-757.0 (RM 612)
- Size: 1 L Plug ‘n’ Clean
- Who it is for: treated and untreated outdoor timber, including decking and garden furniture
Soap is a low-pressure job. Fit the bottle, twist the Vario to the detergent setting, apply, wait, then rinse on a wide fan. High-pressure soap just wastes cleaner and sends foam into the drain. Trafalgar also has a 5 L wood cleaner at £17.50 if the deck is large and you will refill a tank. The 1 L Plug ‘n’ Clean is the everyday bottle.
Do not put stone cleaner on timber because it came in a Home box. Do not put deck cleaner on a car. Match the detergent to the surface. Bleach on composite or coloured boards is a common way to void a warranty and bleach the lawn.
Skip it if the only dirt is loose dust. A plain rinse on a wide fan is then enough.
How not to rip the grain
Treat timber and composite as two materials.
Softwood and hardwood. Sweep. Soap if the film is green. Wide fan, with the grain, keep moving. Further back than you think. A close rotary jet raises the grain and leaves a fuzzy deck. If you use the T 5, raise the jets and do not lean on the handle. Test a hidden board first. If the surface furs, stop and finish with a hose and a deck brush.
Composite. Check the board maker. Many UK ranges allow a low-pressure fan rinse and forbid a pencil jet. If the booklet is missing: wide fan, 30 cm or more, with the boards, no rotary, no bleach. Do not fire into the gaps. Water forced under the boards sits on the joists.
What the dirt blaster is for. Stone, not timber. The same jet that lifts moss from concrete will chew a board in a few seconds. If a stain will not move on a wide fan and soap, it is a brush job or a replacement board, not a reason to click the rotary on.
A patio and a drive can take more punch. Decking cannot. Other machines sit on the reviews index. Petrol is the wrong tool here. See the petrol guide only if the job is a yard of concrete, not a set of boards.
How to choose
- Own nothing, timber deck, tap and socket. K4 Power Control Flex Home. Add wood cleaner. Leave the dirt blaster on the hook.
- Already own a K4 or K5. T 5 on the high setting, plus wood cleaner.
- Already own the head. Bare K4 Flex if you need a washer. Do not buy a second T 5.
- Long drive as well as the deck. K5, turned down on the timber. That choice is K4 vs K5.
- No socket. Cordless rinse, then a brush. Not a bigger pump.
FAQ
What is the best pressure washer for decking in the UK right now?
A Kärcher K4 Power Control Flex Home, used on a wide Vario or a T 5 on the high setting. 130 bar you can turn down is the useful class. The dirt blaster is not part of the job.
Will a pressure washer damage decking?
Yes, if you stand close, use a rotary jet, or park a patio head in one spot. Wide fan, distance, keep moving. Soap and a brush do more for algae than extra bar.
Can I use a K5 on decking?
Yes, if you turn it down. Buy a K5 for a long drive or a large patio, not because the boards need 145 bar.
Do I need a T 5 for a small deck?
No. A wide Vario and patience will do a 2 × 3 m balcony. The head earns its keep on a larger deck where striping from a lance is the daily frustration.
Can I use the dirt blaster on a stubborn stain?
No. That is how you rip the grain. Soap, dwell, wide fan, then a deck brush.