Grodan Improved Uni-Slab 9.5 x 8 x 4 in | Case of 16 Stone Wool

How a Grodan Uni-Slab Is Built and Why It Matters

Two construction choices define this slab. The first is the wetting agent, which Grodan work through the fibre rather than spraying onto it. Water and feed then spread across the full width instead of running down a channel. Water content and conductivity read the same at both ends of a slab. Without that, a slab develops wet and dry regions and the plant on top of it gets an average of two different environments. The second is fibre orientation. The fibres run vertically rather than lying in a random mat, which moves water down and lets air in from the top. That produces a gradient with a drier upper layer and a wetter base, which is exactly the structure a grower steers against. Each slab measures 9.5 x 8 x 4 in and sixteen come in a case. The footprint takes a four inch block on top of it comfortably, which is how this size is normally run.

Resaturation, Steering Range and Conditioning First

Grodan describe this material as having a high resaturation capacity across a broad steering range. That phrase is worth unpacking, because it is the whole commercial argument. Steering means letting the substrate dry back between irrigations and controlling how far. A wide range means you can take it further down and still bring it back evenly. A substrate that will not re-wet cleanly channels instead. The next feed then runs past the root zone rather than through it, and the lever is gone. Condition the slabs before planting. Stone wool leaves the factory alkaline, and Grodan publish a soaking routine in pH-adjusted water to bring it into range. Skipping that step costs the first fortnight in iron lockout. Cut drainage slits after the slab has been conditioned and drained, not before. Barcode data is not on file for this item. A distributor publishes 8718232040566 against the same slab, and it has been left uncopied rather than assumed.

Key Features

• Case: Sixteen slabs to a case
• Slab size: Nine and a half by eight by four inches
• Range: The Improved range, with an advanced wetting agent in the fibre
• Even distribution: Water content and conductivity read the same across a slab
• Fibre orientation: Vertical rather than a random mat, which builds a gradient
• The gradient: A drier top and a wetter base, which is what steering works on
• Resaturation: High capacity, so a deep dry back still re-wets evenly
• Block fit: The footprint takes a four inch block on top
• Before planting: Condition in pH-adjusted water, as Grodan direct
• Drainage: Cut the slits after conditioning and draining, not before

Technical Specifications