Thread: Grass Under deck

its called a weed mat
you can buy it from bunnings not sure if they have taken over in nz yet
i recon a shade cloth would do the same no light = no weeds

Diesel in a watering can...

Roundup (Weedkiller). The deck will stop light getting to the grass. Any physical barrier you put down will stop/slow water draining into the ground

I just weed matted a 6.6m x 4.2m area. Haven't had any problems. This is the way I did it and this is the way I recommend anyone doing it. Just make sure you use the 'pins' that goes with the weedmat to hold it in place so the wind doesn't blow / flap it around.

I second the weed killer.

Good idea to put some screenings 1st to drain any excess water away, perhaps a drain if it holds water, it could rot your posts over time.

I have seen decks close to the ground get weed infested, which becomes a huge hassle for the owners. Throw down the plastic weed mat, should stop them

Go with the weed mat or shade cloth.

Like we don't have enough problems already finding fresh water?

If the grass has any appreciable height, I would hit it down to near ground level (1/4 in, 6mm) and rake it out before installing weedmat. The weedmat is intended to prevent frsh weeds emerging from the ground, rather than killing off existing 2in, 50mm or higher crops. Pinning regularly will keep the mesh in place, or a thin layer of 3/4 plus rock will hold it down. Try and keep the mat tight around stump holes so weeds don't end up with a lot of built in escape paths.

Weedkillers will kill off anything currently growing, but tend to encourage more persistant weeds which can establish without competition from existing vegetation, so regular spraying becomes necessary if the area can get any light.

Just out of curiosity, has anyone ever tried washing a weed kill through your decking? would this damage the deck?
I would assume you would need to use straight weedkill and then wash the deck off well with water which would inturn dilute the weedkill as it goes below.

Originally Posted by dan76n

Just out of curiosity, has anyone ever tried washing a weed kill through your decking?

Had a pressure pot of mixed glyphosphate in a bench in the barn heat up the other week, then blow some solution out of the pot. This left significant salt staining on the floor after evaporating, and stained the ply benchtop as well.

I suspect that applying through the decking would set up rust in the fasteners (even SS) and stain the decking timbers as well. Also not good stuff to let get tramped onto floor coverings or meet up with pets.

If you wash off within 6 hours, the runoff would dilute the applied mix below. I suspect the decking would absorb the solution within a few hours, and become a long lasting threat to tramping inside or animals.