Thursday, May 20, 2010

Which felt?

Felipe wrote:

"Hi Matt , My name is Felipe , i'am form Chile and i'm going to star my own green wall, but I have a question because i don't know what kind of felt i need, if i can use the felt used for hydroponics that i can get in many stores or have to be an special felt? please please try to answer. I'll be very grateful

Big Hug

The felt I use (MRM) is made for greenroof installations. A hydroponic felt may be similar but I'm not sure. Click here for a data sheet on the felt I used. That should help with comparisons. Here's the basic information cut and pasted from the sheet:

Moisture Retention Mat is composed of high-quality, recycled, non-rotting, poly-propylene fibers.

Moisture Retention Mat is used in the Hydrotech Garden Roof Assembly to retain moisture and nutrients for use by the vegetation layer.

THICKNESS: 3/16 in. (≈200 mils)
SIZE: 7.5 ft. X 100 ft. (2.3m X 30.5m) - in rolls
(715 sq.ft. effective coverage)
WEIGHT: 16 oz./yd2 (542 g/m2) 0.11 lb./sq.ft. (0.54 kg./sq.m.) - dry;
1.2 lb./sq.ft. (5.9 kg./sq.m.) - wet
WATER RETENTION CAP.: ≈0.13 gal./sq.ft. (5.3 l./sq.m.)

(ASTM D4632) (ASTM D4632)
TRAPEZOIDAL TEAR: 145 lb/in2 (0.644 kN) PUNCTURE STRENGTH: 240 lb (1.07 kN)
(ASTM D4533) (ASTM D4833)

Good Luck,



  1. Hi, where did you purchase the moisture retention mat that you spec out here?

  2. Hi Matt,
    Great Blog, lots of instructions and very clear.
    I´m about to start making my own green wall, and I have found some www suggesting to use Rockwool as an easier/cheaper substitute for the felt. Have you ever tried with it. Any idea about advantages or disadvantages. Thank you very much.
    Alex from Argentina.

  3. Hey Matt, we are a group of people planning a vertical garden including an Aquaponics system on a building made out of Pallet Racks. It's hard to find the same Materials here in India that you have in the west. Do you know if theres a list of felt products ever used for vertical gardens or can you post some of these or send a mail ( contact sheet at )? Would be awesome.

    You can follow the process over the next months on the blog: