Flexamat Flexible Concrete Mat

What is Flexamat?

Flexamat is a tied concrete block mat — permanent hard armor that arrives rolled up on a truck. Terradyne installs Flexamat — articulated concrete blocks cast on a geogrid mat that rolls out as hard armor and stays vegetated between the blocks.

The blocks take the flow; the gaps between them grow grass; the geogrid underneath ties every block to its neighbors so the mat flexes with the grade without coming apart. It is the middle answer the hard-armor family was missing — more armor than a reinforced grass mat, more landscape than a rock section.

Armor you can mow

The vegetated joints are what separate Flexamat from a rock section. Terradyne places Flexamat as permanent vegetated hard armor on channels and slopes. Where the surface must double as access — a maintenance path, a mowable channel — the tied-block format is what keeps the armor usable. A riprap channel is protected but lost to use; a Flexamat channel is protected and still part of the site.

A category the regional guidance recognizes

Articulated concrete block armor is an engineered velocity-dissipation option in the regional standard, on the same terms as rock and baskets. Under iSWM, articulating concrete blocks may be used for velocity dissipation when the designer provides calculations that document the size and dimensions for the design storm flow rate and velocities. The mat is chosen by the numbers — flow rate, velocity, section — not by catalog preference.

Permanent, in the permit's terms

The vegetated block mat plays directly into the compliance endgame. Final stabilization under TXR150000 requires uniform perennial vegetative cover of at least 70% of native background density, or equivalent permanent stabilization measures. A Flexamat section covers both halves of that sentence at once — a permanent measure that also grows the vegetative cover through its joints. That dual identity is worth real money at closeout: the section does not wait on grass density arguments the way a plain seeded channel does, and it does not trade away the green finish the way a rock section would. It is finished when it is built, and greener every season after.

Rolled out, not placed block by block

The roll-out format is the labor story: armor that arrives as a mat and unrolls onto prepared grade instead of being placed a block at a time. Subgrade preparation is most of the craft — the mat wants smooth, compacted, seeded grade with no voids underneath, and it rewards that preparation by going down in panels instead of pieces. Anchoring and edge terminations follow the design, and the grass does the rest of the finishing. Panel joints get tied per the detail, terminations get keyed so flow cannot get under the first block, and the seeded joints get the same establishment care as any other planted surface on the site.

Reading a section after a storm

An installed mat makes its own inspection easy. Healthy sections read uniform: blocks seated, joints green or greening, edges tight to the terminations. The warning signs are just as legible. A block row standing proud of its neighbors means the subgrade settled or washed underneath — water found a void and is working on it. Bare joints in a section that should have grown in mean the soil beneath ran short or the water never came, and bare joints are how a vegetated mat slowly becomes just a mat. And an edge lifting at a termination is the one to fix the week it appears, because every storm after that has a handle to pull on. All three trace back to preparation and establishment rather than the product — which is the pattern with every armor on this page: the material is rarely the failure; the ground it sits on usually is.