Thickness, use and stud centres
The spans in the table below are the maximum unsupported centres from BBA Agrément Certificate 00/3675 (Issue 4, 31 July 2024), Table 12. Every board edge needs support, and you should confirm the live datasheet and current BBA status before you specify.
| Thickness | Typical use | Max stud centres | Shop |
|---|---|---|---|
| 4mm | Overlay on a sound floor, including over suitable underfloor heating once the heating build-up is complete. | Not listed as a spanning wall board | Buy 4mm |
| 6mm | Overlay with a little more rigidity on floors and existing tiles. | Not listed as a spanning wall board | Buy 6mm |
| 10mm | Walls on closer-spaced studs. Also used on floors over a solid substrate. | 300mm | Buy 10mm |
| 12mm | Same job as 12.5mm. The shop stock for this is 12.5mm. | 400mm (as 12.5mm) | Buy 12mm |
| 12.5mm | Standard wall board on timber or metal studs. | 400mm | Buy 12.5mm |
| 20mm | Walls on 600mm centres. Useful where the background is uneven. | 600mm | Buy 20mm |
Walls
On timber or metal studs, thickness is about how far the board can span between supports: 10mm needs 300mm centres, 12.5mm needs 400mm, and 20mm needs 600mm. If you searched 12mm, buy 12.5mm, which is the wall sheet we stock.
Floors, overlay and UFH
4mm and 6mm are the usual overlay on a sound floor, including over suitable underfloor heating after the heating build-up is complete. Those thicknesses are overlay sheets, not spanning wall boards in the BBA table. wedi PreLine boards take UFH pipes in the channels, and you should check the datasheet for the floor build-up before you order.
XL and XXL sheets
If you want fewer joints on a long wall, XL and XXL are larger sheets of the same wedi board system. The thickness rules still apply.
Shop wedi boards
We stock the standard thicknesses plus XL and XXL, and the datasheet is on each product page.