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Where I live, I've noticed many buildings have a stone/gravel barrier between the building foundation and the lawn or flower bed. Why is this? Does it prevent insect or pest infiltration of the structure?

barrier1

barrier2

  • Picture one shows accessibility as the primary reason to me – Christiaan Westerbeek Jun 28 '18 at 21:41
  • Your Stella d'Oro daylilies are thriving. The skimmia (needs acidic soil) not so much. When replacing look for plants that do not need acidic soils (concrete foundation, lime, alkaline soil pH). – stormy Jun 28 '18 at 23:01
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    Besides drainage, rocks against the foundation lower the amount of periodic lawn maintenance at the edge of the building... no weedwacking against the foundation if there are rocks / weedbarrier there. – Mike Pennington Jun 29 '18 at 3:38
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    "Where I live ..." -- Where do you live? It might make a difference in the answer. (e.g. with respect to local weather conditions, local insect populations, local building practices, etc.) – R.M. Jun 29 '18 at 14:27
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    @Megatron Your question was superb. Look at the amount of readers and commenters! Such a simple question yet fabulous for understanding basics of drainage. This question should be reaching some sort of reward numbers! – stormy Jul 1 '18 at 22:48
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You don't want water-retaining soil sitting against the building because this causes damp problems. Creating a porous soakaway like this will mean any water sinks to a lower level than would cause any harm to the building.

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    Does this mean that there is no soil below the rocks to a specific depth? – Megatron Jun 28 '18 at 21:13
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    It probably depends on the nature of the building. If it has a basement then it's a good idea to minimise earth in contact with the masonry. If not then it should have a damp proof course somewhere in the construction, above which it's definitely bad to have wet material in contact with the masonry, but in any case it's sensible to try and keep water away from the foundations. They may also just be decorative. – David Liam Clayton Jun 28 '18 at 21:36
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    @JacquesGaudin if the water table is high, it wouldn't help. In most cases though, the water table is lower but after strong rains it takes time for the water to seep down through the soil, while rocks+sand make it much faster and prevent a "swamp" around the house. – IMil Jun 29 '18 at 2:01
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    We recently replaced some sacrificial plywood around the base of one of our buildings, the we now have gravel like this (and dimpled foundation membrane) around the area specifically to improve drainage. – mu is too short Jun 29 '18 at 3:57
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    Obviously depends on your local climate, but this is the answer. My cellar was damp until I dug a trench all the way round and filled it with pebbles like this. Now moisture can evaporate quickly from the walls. – RedSonja Jun 29 '18 at 10:42
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Perhaps I missed something in the other answers. The one and only reason is because of SPLASHING. Rain over the gutter, a hard sideways rain will splash mud/soil onto the siding. Not good for siding as the mud tends to hold moisture too long and can cause rot as well as a dirty 'skirt' on your siding.

The gravel, drain rock, cobble or even the lava rock as pictured in the first picture however needs to be below the siding at least 4" otherwise the rock becomes a moisture problem. That first picture with the lava rock and the trap? That lava rock is touching the siding. The siding appears to be concrete. Concrete foundations need to be coated with asphalt for protection. Concrete is very much harmed by moisture. The picture with the 4X6 holding in cobble? If that rock is as close as I think it is to the siding, that will rot the siding if it is not at least 4" below the siding.

Before the cobble or gravel gets installed this is when landscape fabric is necessary. Not to prevent weeds but to prevent the cobble sinking down into the soil and the soil replacing the cobble.

The following is off topic but hopefully helpful...

I wish I could find a more common mulch people could use instead of chunky bark. This is not for weed suppression it is to unify a landscape by covering the soil with a regular texture. Chunky doesn't work. Fine works far better for aesthetics and for decomposition sometime in the near future.

The only mulch I will ever use in the landscape is human poo mixed with sawdust and completely decomposed professionally. Grins. That 4"X6" (not pressure treated)? is a great condominium for insects and other animals; slugs, snails, earwigs, pillbugs...and many more. Not at all necessary or even beneficial.

I lived and breathed construction in all forms for half a century. The only reason and it works well, for using cobble at the base of an outside wall, is for splash.

If this is your lawn here is the best way to fix those edges. Also look up how to produce and maintain a cool season lawn crop! On our site, not on Scott's or Ortho...Use a hose or string, a center to make a set radius to change when changing point of radius to the outside of the lawn. Keep radius curves consistent for each curve. They can change radii every curve but not during each curve. lawn edging the right way

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    This answer goes from "totally on-topic" to "somewhat related" to "totally unrelated". Maybe try to remove the unrelated parts? – hoffmale Jun 29 '18 at 17:42
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    @hoffmale or just make it clear that the topic has shifted slightly after 2nd paragraph. "Talking about landscaping the base of buildings in general..." – Jeutnarg Jun 29 '18 at 18:56
  • Thanks for the feedback. Jeutnarg I chose your option. I like giving 'bonus material' and it drives everyone nuts. – stormy Jun 29 '18 at 19:33
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My guesses are that it just looks a lot neater and also prevents weeds from growing near the foundation. If weeds and their roots are allowed to grow there you would have to be constantly digging them out, and roots are already hard enough to get out of the ground without having to dig near or under that area. Another reason, I think, would be because it is a more permanent solution to weed prevention instead of mulching. Mulching has to be (or should be) removed and/or replenished yearly to maintain an attractive appearance. Lots more work to do that way.
Yet another reason may be to keep water draining away from the foundation. And as you say, reduce the likelihood of pest/vermin infestation, since animals and insects have an easier access to the house through soil and grass. Possibly a combination of all of the above(?)

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    After looking at the picture again, there appears to be what looks to me like a rat trap in the corner, the black thing sitting on top of the brick paver. Maybe that homeowner had or knew of rat problems in the area? – Miss Tinker'smom Jun 28 '18 at 20:25
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    Speaking as someone who has rocks 3/4 of the way around my house, weeds still grow in rocks... just in much lower densities. Weed barrier under the rocks helps you pull them out, but you get them no matter what. My primary reason for using rocks was drainage and no lawnmowing / weedwacking on the sides of my house. – Mike Pennington Jun 29 '18 at 3:35
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    From experience, rocks around a foundation do not prevent weeds from growing. They just make them harder to remove, because you can no longer use a tool like a hula hoe (a.k.a. stirrup or scuffle hoe.) – TKK Jun 29 '18 at 22:05
  • Oh. Like I said, it was just a guess. It looked denser in the picture to me. My humble apologies. – Miss Tinker'smom Jul 1 '18 at 2:41
  • But wouldn't it make sense to lay a weed barrier under the gravel to prevent them in the first place? That's what I would do. – Miss Tinker'smom Jul 1 '18 at 2:42
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Some jurisdictions require non combustible mulch i.e. gravel next to the structures. Several buildings have had fires started from discarded smoking materials in combustible mulch.

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