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How to line a wooden window box when the base is open slats

Updated: October 2026

Soil is on the boards, and the box you have just watered is the reason. The base is open slats, the listing included no liner, and the compost had nowhere to stay. This is how to line a wooden window box in that case, and when a liner-included line is only a special feature. The Products Compared editorial team used the amazon.co.uk listings saved on 15 October 2026, plus RHS and UK planter guides. There is no life in years from a lab. Which box to buy is on the [wooden window box comparison](/hub/door-and-window-security/wood-window-box).

Soil is on the boards, and the box you have just watered is the reason. The base is open slats, the listing included no liner, and the compost had nowhere to stay.

Our top picks

NUPTIO Nuptio white window boxes

Best overall

NUPTIO Nuptio white window boxes
6.4/10about £19.98
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Hortico Hortico 76 cm window box

Rank 2

Hortico Hortico 76 cm window box
8.8/10about £26.99
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Hortico Hortico 51 cm pair

Alternative

Hortico Hortico 51 cm pair
6.7/10about £38.78
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On this page
  1. 1.When the compost will fall through
  2. 2.A sheet you must pierce, or a fabric that drains
  3. 3.What liner included means on these listings
  4. 4.Fit the liner, then stop

When the compost will fall through

Line the box before compost goes in if the base is open slats. Both Hortico troughs ship that way: slats, no liner in the bullets. UK reviews say the gaps let soil and water out until a bag or a membrane is added. A note that lining is optional on a solid drained box does not apply here. Creosote is not a substitute under the Creosote Regulations 2003. The shared reviews are on the buying guide.

A sheet you must pierce, or a fabric that drains

A waterproof liner is a plastic sheet, a damp-proof membrane, a rubble sack, or the compost bag the RHS and Bents both allow. Press it into the corners, stop around the soil line, and pierce it in line with the slats. Without those holes the liner is a bucket. A few staples hold better than glue. A breathable liner is landscape fabric, hessian or coir, and it usually needs no holes. Do not claim a life in years for either. The crock rule for holes larger than about 2.5 cm is on the how to plant page.
NUPTIO Nuptio white window boxes

Testsieger

NUPTIO Nuptio white window boxes
6.4/10about £19.98
View offer

What liner included means on these listings

Read the box contents, not a special-features line alone. Both Horticos include the box or the pair only. Growscape claims a removable plastic liner, drainage is No, and UK texts include a second box that arrived with no liner. That is not a 15 cm trough. Toddmomy names a clear liner only on the special-features line, so treat it as unconfirmed. Tbest is 4 × 8.9 × 4 cm. Do not line that as a trough. Who should skip a type is on the best wooden window box page.

Fit the liner, then stop

Fit the liner dry, push a waterproof sheet into the corners, pierce it where the slats are, and use a few staples. Fabric does not need those holes. Do not drill a Hortico base that already drains through slats. A sealed sheet with no holes is a bucket. Then stop. Compost and watering are the planting page. A liner does not certify the timber, and it does not make a 7 cm tray into a 24.5 litre trough. If soil is already falling through, you have a liner problem, not a variety problem. A qualifying amazon.co.uk purchase can earn a commission at no extra cost to you.

Common questions

Do I have to line a slatted wooden window box before compost goes in?
Yes. An open slatted base will not hold compost, and both Hortico listings here ship without a liner. Reviewers describe soil and water leaving the gaps until a bag or a membrane is added. A solid box in a maker’s guide, where lining is sometimes optional, is not these slats. Fill only after the liner is in.
Can I use the compost bag, and do I have to make holes in it?
Yes. The RHS describes an old compost bag with holes punched in the base, and Bents allows the same sort of plastic sheet. The holes must line up with the slats, or the bag holds water and the box becomes a bucket. Stop the plastic around the soil line rather than folding it over the rim. A few staples hold it better than glue.
Is a breathable fabric liner better than plastic for a slatted base?
Fabric lets water through without a piercing step, so it is harder to turn into a swamp. Plastic is fine if you pierce it in line with the gaps. Neither has a stated life in years on these listings. Choose fabric when you want the water to leave on its own, and plastic when you already have a tough bag and you will cut the holes.
What happens if I line the box and forget the holes?
A waterproof liner with no holes is a bucket. Roots sit in water, and the timber stays wet against the compost. Breathable fabric usually does not need those holes. If you have already fitted a sealed sheet, pierce it before you water, in line with the slats, rather than waiting to see whether the plants cope.
Which boxes in this set already claim a liner, and can I trust that line?
Growscape claims a removable plastic liner in the bullet, and a UK review of two boxes said the second had none. Drainage on that listing is No. Toddmomy mentions a clear liner only on the special-features line, not in the bullets, so treat it as unconfirmed. Hortico does not claim a liner at all. A special-features line is not an item in the box.
Should I staple the liner, and should I drill a box that already has slats?
A few staples or tacks hold better than glue, and a dense line of metal is unnecessary. Do not drill a Hortico base that already has slats. Those gaps are the drainage, and drilling does not replace a liner. Drilling a uPVC window frame is a different problem and is not part of lining the wood.

Related pages

Plastic trough or wooden window box

Wooden window boxes

Wooden window box on a balcony or in a rented flat

Best wooden window box for compost or table flowers

Wooden window box buying guide: height, liner, size

How to plant a wooden window box without losing soil

Sources

Public sources used for this comparison. Prices, stars and review counts are amazon.co.uk figures from the listing extracts dated 15 October 2026.

  1. Consumer Rights Act 2015, sections 9 to 11 (retrieved 15 October 2026)
  2. Creosote Regulations 2003 (retrieved 15 October 2026)
  3. HSE biocides overview (retrieved 15 October 2026)
  4. Wood Protection Association, Use Class 3 (retrieved 15 October 2026)
  5. RHS: how to plant up a container (retrieved 15 October 2026)
  6. RHS: roof gardens and balconies (retrieved 15 October 2026)
  7. GOV.UK: how to rent a safe home (retrieved 15 October 2026)
  8. Inveka: drilling into uPVC windows (retrieved 15 October 2026)