Landscapefilter - Is this a proper wall?

September 9, 2012 7:57 PM

Landscaping - having a (basalt) stone wall built. Loose rocks on top normal?

First time hiring a landscape contractor to do a bunch of yard renovations. One of the items is to build a basalt stone wall.

Some of the stones on the top of the wall are very small (weigh only a few lbs) and the wall is constructed without any mortar.

It is me or is this not how a wall should be built?

It feels like after a hard rain/wind or a squirrel running along it, the whole top layer may be gone.

Pics 1 2 3

posted by wongcorgi to Home & Garden (10 answers total)

That is about how they all look unless you pay a specialist (like a master stonemason). Building a mortarless stone wall is no easy task. It is hard, backbreaking labor and the wall looks pretty steady. When you have a stacked wall used as a retaining wall (as an engineer I don't really think it is a good idea)you want a lot of openings in the wall to let out water. In general you want the stones to get generally smaller as you go up a wall since that makes it less top heavy. Even the small stones are surprisingly heavy. Any mortarless masonry wall is going to require maintenance of replacing stones periodically as heavy rains will shift it some but it will take livestock or such to actually move a stone. planting the top and bottom with a shallow rooted plant like turf will help a LOT with stability. You don't anything with big roots like trees or even shrubs near it though.
posted by bartonlong at 8:05 PM on September 9, 2012

It is me or is this not how a wall should be built?

It's you. Walls constructed without any mortar is exactly how walls have been traditionally built. The wall out the back of my house is about 300 years old and it isn't going anywhere. Yours looks perfectly sound to me.
posted by DarlingBri at 8:17 PM on September 9, 2012

Response by poster: Thanks for the info. Some of the rocks on top weigh less than 1 lb which makes me think that they are more sitting on top of the wall than part of it.

Is there a way to properly test the wall before the rest of the work is completed? Ie. jump on the dirt behind it, soak the backside with water?
posted by wongcorgi at 8:26 PM on September 9, 2012

Personally I would want flat edged stones used across the top ("capstones") so the retaining wall can also be used for seating, although I'm not sure if that is part of your greater plan to have seating or if there is difficulty gaining flat stones.

heres a link that might be useful for you
posted by Under the Sea at 9:14 PM on September 9, 2012

Basalt is a bitch to dry wall in. Because it is igneous, there are no fault planes, so you don't normally have nice flat edges to lay against. (give me sandstone any day!). There are normally weird bumps and hollows that mean the stone will rock a bit, unless you chink it with small pieces of rock. This is time consuming. You could try to shape the rock, but I haven't had any luck (The only basalt I've used was monsonite - (bloody bloody hard - an excavator took 2 weeks to chip through a 2 metre trench))

From the photos it doesn't look like your landscaper has either chinked or shaped, so I hope the wall isn't very tall and it is laid back at an angle.

Suggested things to do are:
1. Give the stones below the capping a shove with your hands - maybe they are firm - so kudos to your builder. But if they move - get the builder back. I like to compact the back of the wall while as the wall is increasing so that you know the stone can't move back
2. Get your capping stones to bridge across the joins of the stone below.
posted by insomniax at 12:47 AM on September 10, 2012

My grandfather, a surveyor, civil engineer, and coal mine executive, had a mantra: "Land is liquid!" You can build anything so long as you keep that in mind.
posted by The 10th Regiment of Foot at 6:51 AM on September 10, 2012 [1 favorite]

I have a wall that looks exactly like that in my backyard, and it's been there for over 30 years and hasn't led to any issues whatsoever.
posted by TinWhistle at 7:21 AM on September 10, 2012

Totally fine. I've built a mortarless retaining wall of similar height out of quite round rock and it still stands just fine. Yours is much more angular (and thus better locked together).

Some of the rocks on top weigh less than 1 lb which makes me think that they are more sitting on top of the wall than part of it.

By definition, if you have a dry stacked wall, the whole thing is just sitting on top of the rock below.

The small rocks on top of your wall are there to even out the top edge of the wall - otherwise, it would be very rough. The soil and vegetation behind should, over time, help hold those in place. The small rocks lower down look like they are there to help position the larger rocks (and build a solid wall). All together, your wall looks fine.
posted by ssg at 8:39 AM on September 10, 2012

Plant some sedum or other stonecrops on the top and treat it like a rock garden. Some dirt, roots, and plants will make a nice cap to hold the top layer together.
posted by General Tonic at 2:52 PM on September 10, 2012

Looks good to me, and I work in the industry. You can take off the smallest if you want; it won't change anything about the integrity of the wall and they may fall off anyway.

This is a dry stack wall, and it's perfectly fine in this application. If you want a mortared wall you would pay significantly more. Water is not going to wash it away because there's plenty of room for seepage between the stones.

PS: when hiring a contractor always ask for references that you can call or drive by. Ask for pictures of what something will look like when it's finished. It sounds like you had something different in mind than what was built for you so ask for clarification for everything going forward.
posted by oneirodynia at 4:32 PM on September 10, 2012