A reno mattress is a shallow, wide gabion unit, typically 150 to 300 mm deep, divided by internal diaphragms into cells and filled with small graded stone. Its geometry is what defines it: where a gabion basket is a block for building mass, a mattress is a blanket for covering area. It is used as a flexible, permeable, erosion-resistant lining for channel beds and banks, slope faces and structure aprons.
Construction and fill
Mattresses are manufactured from double-twisted hexagonal woven steel wire mesh to BS EN 10223-3, or from welded mesh, with the wire protected by heavy zinc or zinc-aluminium coating and, in aggressive or marine environments, an additional polymer coating. Internal diaphragms at roughly one-metre intervals hold the stone in place and stop it migrating along the unit under flow. Because the mattress is shallow, the fill stone is small — commonly 70 to 150 mm — which is a decisive economic advantage where large armour stone is scarce or expensive. Units are laced or ringed together on site so the whole revetment acts as a single continuous mass.
Where mattresses are used
Typical applications are channel bed and bank linings, aprons downstream of culvert outlets and structures, scour protection at bridge piers and abutments, wave protection on reservoir and canal slopes, and the toe of larger rock revetments. The mattress can be laid over a shaped slope and follows minor deformation without cracking, which is the principal advantage over a rigid concrete facing. Where a vegetated finish is required, the voids can be filled with soil and seeded or planted through the mesh, and once established the root mat contributes to the surface stability.
Design considerations
Selection is on thickness against the design velocity and shear stress, following the guidance in the CIRIA and CUR Rock Manual (C683) and the manufacturer’s declared performance. Three details govern durability. A geotextile or granular filter beneath the mattress is mandatory unless the subsoil is coarse enough not to be washed through the fill — without it, the bank hollows out behind an intact-looking mattress. The upstream and downstream ends must be terminated in a cut-off or key trench so flow cannot get beneath the blanket. And the toe must be taken below the anticipated scour depth. Coating specification should follow from the water chemistry and the design life, not from habit.
Mattress or gabion basket
The two are the same product family solving different problems. A gabion basket, typically 500 mm or 1 metre deep, provides mass and is used for retaining walls, weirs and structural bank toes. A mattress provides coverage and is used for revetment and scour protection. On a river bank scheme the usual arrangement combines the two: gabion baskets forming the toe and lower bank where retention is needed, mattresses covering the upper bank and the bed where erosion is the only issue.
Related ViaCon solutions
ViaCon supplies gabion baskets, mattresses and associated geotextiles for erosion and scour protection. See our geotechnical solutions range. Related glossary entries: gabion, rock armour, revetment and erosion control.
Frequently asked questions about reno mattress
What is a reno mattress?
A reno mattress is a shallow, wide gabion unit, typically 150 to 300 mm deep, divided into internal cells and filled with small graded stone. It is laid as a flexible, permeable erosion-resistant blanket over channel beds, banks and slopes.
What is the difference between a reno mattress and a gabion basket?
Geometry and purpose. A gabion basket is typically 500 mm to 1 metre deep and provides mass for retaining structures. A mattress is shallow and wide and provides surface coverage for erosion and scour protection.
What size stone is used in a reno mattress?
Fill stone is small relative to rock armour, commonly in the range of 70 to 150 mm, because the mesh binds the stones into a single mass rather than relying on individual stone weight for stability.
Does a reno mattress need a geotextile beneath it?
Almost always. Without a filter layer, water moving through the mattress washes fines out of the bank beneath and the slope hollows out while the mattress still looks intact. The filter is a geotextile or a graded granular layer matched to the subsoil.