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I'm looking for a solution to control weed growth on a patio out of paving stone. The weeds are growing the the joints between the stones as can be seen in the picture. Two methods have been proposed:

  1. Jointing the gaps with mortar.
  2. Remove the stones and ad a fleece under the paving stones.

Method 1. is much cheaper than method 2. So I'm inclined to use method 1.

What are the pros and cons of each method?

Are there any other alternatives which suppress weed growth sustainably and in the long term?

Patio with paving stones

  • Jointing with mortar will be some considerable effort, will alter the appearance, and probably won't work well enough to justify the effort. Pulling up the stones and putting down fabric will be way, way too much effort. Just pull the weeds while you ponder the matter further. – Jim Stewart Mar 13 at 12:16
  • @JimStewart I found this mortar and the videos demonstrate that it seems to be quite easy to do..youtube.com/watch?v=vIO7dYHpCk4 – CuriousIndeed Mar 13 at 12:23
  • OK then, but that is the absolute most I would ever do. Personally a few weeds (or even more than few) wouldn't upset me. And those "simple, nifty solutions can sometimes go awry. – Jim Stewart Mar 13 at 13:17
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From the picture you already have your patio installed. To implement the polymetric sand solution or the mortar solution requires that you

  1. Pull up the pavers
  2. Clean out the sand/dirt between the cracks
  3. Reinstall the pavers
  4. Apply polymetric sand/mortar

I've been working on the same issue but I am trying to not pull up the pavers.

The Problem:

  1. Dirt gets into the cracks between the pavers
  2. Seeds blow onto the patio and get into the dirt
  3. Seeds grow and send roots down between the pavers

So, polymetric sand/mortar provides less opportunity for dirt which reduces the chance for seeds to sprout.

Putting weed blocker under the patio fails to address the root cause.

My Solution

I know I'm going to catch some heat for this but here goes. I have a large paver patio and I hate pulling weeds so I decided to try salt to prevent weeds. Salt gets down into the cracks and makes an unfavorable environment for seeds to sprout.

  1. Bought a 20 pound bag of table salt for $7 (not rock salt, table salt is super ground super fine)
  2. Poured about 3 pounds of it onto the patio
  3. Used a push broom to work the salt into the cracks. Since it was table salt it is very fine and broomed into the cracks nicely.
  4. Using my water hose I wetted down the salt so that it washed into the cracks. Not a major hose down, just enough to get the salt wet and further into the cracks.

The patio looked a little salty for a few days. A rain or two brought the patio back to it's normal color.

The result

  • Weed free patio all summer
  • No salt damage to the pavers

If weeds start to grow again I'll broom in more salt. I'm one year into my experiment - so far, so good.

  • According to wiskeychief's answer, the polymetric sand goes between the pavers (putting it underneath probably doesn't hurt, but isn't required). Therefore, it's a great "after market" addition. However, I'm on board with your "salted earth" technique, as well. Depending on your climate, salting in the late fall may also help prevent freezing, which may help prolong the life of the pavers and the general levelness of the patio. – FreeMan Mar 13 at 16:47
  • Salting will work, but you need to be careful of what is around your patio, some excess salt will wash out and can kill vegetation downstream, i.e. your lawn or other plants you want to grow, and it will be persist in the soil making it difficult to grow anything there in the future. – Josh King Mar 13 at 18:48
  • I worried about what would happen to the plants around the patio. I had no issues wanted plants dying. I'm always amazed how much salt is on the road and how few roadside plants die. You are correct, it is important to be aware of where you are salting. – David D Mar 13 at 19:00
  • I like this answer, too. I dub this the "Brawndo has electrolytes!" method and it sounds very promising. But yes, @JoshKing, better watch out for collateral crop damage. – whiskeychief Mar 14 at 1:05
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You’re right that weed-block fabric underneath the paver bricks is a good idea. You didn’t say if you put these pavers in yourself, but it might already be under there.

Weeds don’t need deep roots (all the way through the bricks). They can take root in the gaps between the bricks (the same can happen in a concrete sidewalk.)

A quality install of pavers will generally finish with a layer of polymeric sand (“paver sand”) that’s brushed into the cracks. The sand acts like mortar by filling the cracks, and it may have some acidity to make it more difficult for weeds to grow. (Then they sweep up the excess). A 50-pound bag of polymeric sand costs only about $4.

This is also recommended as annual maintenance by some installers I’ve talked to. Clean the cracks as best you can, then sweep some paver-sand into the cracks to make a more inhospitable environment for weeds to take root.

  • 2
    Mortar will break and crumble from movement of pavers. – Jeff Cates Mar 13 at 11:22
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That looks like grass rather than weeds and could be coming from "runners" following the cracks in the pavers from the yard.

Carefully dig out and inspect the transition from grass to pavers and see if there are any runners growing into the pavers. If there are, then installing a strip of metal or plastic edging against the grass could be the best solution.

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