Short answer: for a summerhouse floor, use 18 mm underlayment of 1.22 × 2.44 m for €39.95, or 18 mm plywood for €69.70. We only have 18 mm OSB as a half sheet of 0.61 × 2.44 m (€18.80). Concrete plywood is for formwork and damp spots: 12 mm costs €56.05. We do not stock MDF, HPL or birch plywood.
Which board suits your job?
- Summerhouse or loft floor: 18 mm underlayment or 18 mm plywood. Underlayment is the most affordable full sheet. Plywood is made of cross-bonded veneer layers and is therefore stiff in both directions.
- Back panel, partition or workshop wall: 9 mm OSB (1.22 × 2.44 m, €20.50), the most affordable full sheet. Keep OSB dry: it is not a facade board.
- Formwork or damp spot: concrete plywood in 12 or 18 mm, 1.25 × 2.50 m. The film coating releases from concrete and keeps moisture out at the surface. Seal the edges after cutting.
- Cabinets and shelves indoors: 18 mm chipboard (Spano), half sheet of 0.61 × 2.44 m for €18.70. Indoor use only.
- Board you want to paint: white primed board in 10, 12 or 18 mm, 1.22 × 2.50 m, from €80.40.
Sheet materials at Jan Sok compared
| Board | Thickness | Sheet size | Price incl. VAT | Stock | Outdoors |
|---|---|---|---|---|---|
| Plywood | 9 mm | 1.22 × 2.44 m | €38.05 | In stock | See product page |
| Plywood | 12 mm | 1.22 × 2.44 m | €48.70 | In stock | See product page |
| Plywood | 18 mm | 1.22 × 2.44 m | €69.70 | In stock | See product page |
| OSB | 9 mm | 1.22 × 2.44 m | €20.50 | In stock | No, not unprotected |
| OSB | 18 mm | 0.61 × 2.44 m (half sheet) | €18.80 | In stock | No, not unprotected |
| Underlayment | 9 mm | 1.22 × 2.44 m | €22.00 | In stock | No |
| Underlayment | 18 mm | 1.22 × 2.44 m | €39.95 | In stock | No |
| Concrete plywood | 12 mm | 1.25 × 2.50 m | €56.05 | In stock | Yes, with sealed cut edges |
| Concrete plywood | 18 mm | 1.25 × 2.50 m | €74.75 | In stock | Yes, with sealed cut edges |
| Chipboard (Spano) | 18 mm | 0.61 × 2.44 m (half sheet) | €18.70 | In stock | No |
| White primed board | 10 / 12 / 18 mm | 1.22 × 2.50 m | €80.40 / €103.90 / €136.60 | In stock | See product page |
| MDF and HDF | Not in our range | ||||
| HPL and Trespa | Not in our range | ||||
| Okoumé, birch and poplar plywood | Not in our range | ||||
| Flexible plywood | Not in our range |
Prices per piece, including VAT, as of 26 October 2026. The current price and stock are shown on the product page in the shop. Where it says "See product page", outdoor use depends on the glue bond and finish of that board; the product page states what applies.
Further reading
All sizes per type: buying plywood and buying OSB boards. Finishing underlayment: treating underlayment. Chipboard in the shop: chipboard. If you are insulating the wall or floor at the same time, look at buying insulation.
Frequently asked questions
Is triplex the same as plywood?
Triplex is plywood made of three layers of veneer; in the trade the names are often used interchangeably. We sell plywood in 9, 12 and 18 mm. We do not have a separate triplex range or flexible plywood.
Can OSB stand up to rain?
OSB is not a facade board. With prolonged moisture it swells, especially at the edges. Use it under a cover or roofing. More explanation: is OSB water-resistant?
Which board do I use for a summerhouse floor?
18 mm underlayment (€39.95) or 18 mm plywood (€69.70), both 1.22 × 2.44 m. We only have 18 mm OSB as a half sheet of 0.61 × 2.44 m. For the same area you need two of them (€37.60). That also gives an extra joint.
Do you sell MDF?
No. We do not stock MDF or HDF. White primed board is not MDF.
What is the difference between plywood and concrete plywood?
Concrete plywood is plywood with a smooth film coating, intended for formwork and damp spots. We stock concrete plywood in 12 and 18 mm (1.25 × 2.50 m), not in 15 mm. More explanation: plywood or concrete plywood.