World Famous Stone Walls

Obviously, we believe that natural stone is a superior wall building material that is unmatched in its strength, durability and timeless beauty. The oldest stone wall has recently been discovered and has been standing at the entrance of a cave in Thessaly, Greece for the last 23,000 years.  Gave us an idea to look up some famous stone walls that have been around for a while.

Walls of Avila (Spain): Built in the 11th century, these medieval walls, almost one and a half miles long, are still in good condition today. Fourteen meters high and as much as 3 meters thick, these walls have about 90 towers and 9 entrance gates.

The Walls of Constantinople (Turkey):  The original walls were built in the 8th century BC and protected only the Greek acropolis. Constantine moved the walls further out and the present alignment was set in the 5th century AD. They extend 6.5 km from the Golden Horn to the Sea of Marmara. Despite lack of maintenance, many parts of the walls have survived centuries and are still standing today.

The Roman Walls of Lugo (Spain):  The walls of Lugo were constructed over a period of 45 years between 265 AD and 310 AD the walls reach 10-15 meters in height, about 2 km in circumference and completely encircle the old town. The entire circuit survives intact and is the finest example of late Roman fortifications in Western Europe.

The City Wall of Visby (Sweden): Enclosing the Swedish town of Visby, this medieval wall was built in the 13th century and substantially modified in the 14th century. The wall is 11 meters high and 3.5 kilometers long and is still largely intact.

The Walls of Carcassonne (France): The historic French town of Carcassonne is a unique example of a double fortification with the town’s massive defenses constructed on walls dating from late antiquity to the 13th century. Very much intact, the inner wall measures 1286 meters and has 25 towers; the outer wall, with 17 towers, measures 1500 meters.

The Walls of Dubrovnik (Croatia): These defensive stone walls have been considered to be amongst the greatest fortification systems of the Middle Ages, as they were never breached by a hostile army during this time period. The intact city walls, constructed mainly during the 12th–17th centuries, run an uninterrupted course of approximately 1,940 meters (6,360 ft) in length, encircling most of the old city, and reach a maximum height of about 25 meters (82 ft).

Great Wall of China: Probably the world’s most famous stone wall, the Great Wall of China, is also the world’s longest (over 4000 miles) and largest human-made structure ever built in terms of surface area and mass. With wall sections dating back to 208 BC, this wall is a true testament to the amazing everlasting durability of stone.

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Stumbled on a post…

Just wanted to share a great post from a CT landscape designer who talked to us at the NE Grows Tradeshow. Now who wouldn’t like it when their product or idea is called ingenious!?

http://blog.designingeden.com/?p=222

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The Wrong Way to Build a Wall

Last year, almost 40% of our projects included replacing a failed retaining wall, some of those walls less than 10 years old. We don’t typically take photos during demolition to show the owners why the wall failed, but we constantly see the reasons and we take every precaution with NSWS® walls to make sure it doesn’t happen. And that’s why NSWS® walls come with a lifetime warranty.

This blog post is a warning to property owners everywhere that just like with most things in life, you get what you pay for.

We don’t make it a habit to criticize other contractors’ work, but we couldn’t help it in this case. This contractor can remain anonymous but it took everything I had not to knock on that poor homeowner’s door to warn them about their doomed new retaining wall that wasn’t even finished yet!

Basically, there are so many things wrong with this wall that it inspired a blog post. What most people will see as they drive past is the stone work, but what most people don’t know is the reason this stone wall is destined to fail is hidden behind it.

The effects are not immediate, this owner is probably going to be satisfied immediately after the job is finished and even pay this contractor. But the real problems will arise after just a few winter seasons.

The specific factors that set this wall up for failure in this particular case have to do with complete lack of drainage, geogrid reinforcement, footings and structural backfill, all very crucial components of a structurally sound retaining wall.

You can see from the pictures, that not a single drain pipe or weep hole was installed. No footing was installed prior to building this wall. Also, building the wall and backing it with mortar against the original clay soil will result in significant movement of this wall during the coming winter months. Furthermore, they are building this wall completely vertical with no batter to it.

Our only (very frustrating) assumption is that this contractor provided a low bid to get the job and cut costs where the customer could not see. Depending on the site, these “invisible costs” are usually about 25% of total wall cost. This company eliminated a significant amount of site work, footing, drainage and backfill requirements. Unfortunately, with none of those precautions taken, this wall will see significant differential settlement and there is no doubt in our minds that it is only a matter of time before its imminent failure.

So homeowners, please remember that just like a good book needs to have more than a pretty cover – a beautiful stone wall needs to be structurally sound to last you generations.

And for your future stone wall projects remember that even small retaining walls have to contain enormous loads and withstand our harsh New England winters.

A structurally sound retaining wall must meet the following two requirements:

  1. The wall is structurally capable of withstanding the earth pressure applied to it – this means structural backfill and proper drainage and at least a 3-4° batter.
  2. The foundation of the wall is capable of supporting both the weight of the wall and the force resulting from the earth’s pressure acting upon it – this means a proper footing (see our last post about footings).

And this is just another reminder that not all walls are created equal.

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Footings

As spring rapidly approaches here in New England and the snow starts to melt away, we are getting many excited and anxious calls about outdoor and especially stone wall projects. One of the questions that we are often asked is “What kind of a footing is required for my wall?” So we decided to post about footings.

A footing distributes the weight of the wall over a wider area, reducing the downward pressure of the wall’s weight.  Basically, the footing transmits the load into the soil. Depending on various factors such as wall height, retaining requirements, architectural features, etc., either a concrete footing or a crushed gravel footing is usually used.

A solid concrete footing is mostly required for walls HIGHER than 4 feet. The concrete footing is typically reinforced with rebar, increasing the tensile strength of the concrete footing.

Reinforced Concrete Footing*

For walls LESS than 4 feet high, another much more economical type of footing – a gravel footing, can be used.

Crushed Gravel Footing*

For a typical 4 foot retaining wall at NSWS, we usually recommend a 30 inch by 30 inch base filled and properly compacted with approximately 24” of crushed ¾”stone or gravel. The bottom of a wall should be below grade approximately 6” or 1/10th of the exposed wall height.

The general idea here is that any water that may penetrate the footing will travel through the crushed stone or gravel and allow the wall to remain stable.  As long as a footing remains relatively dry during the winter months, there will be no differential settling caused from the infamous New England freeze and thaw cycles.

* Source: “Stonework: Techniques and Projects” by Charles McRaven

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New England Grows Expo

NSWS™ has had a very busy fall resulting in some blog radio silence. Our 2011 resolution is to continue sharing great material of all things stone and walls!

This month, we are in the midst of preparing for an exhibition at one of the largest and most popular horticultural and green industry events in North America – New England Grows.

We are bringing full size product samples of our stone walls and really looking forward to meeting landscape architects, designers, contractors and many other green industry professionals.

We welcome anyone attending the expo to come by and visit our booth! We will be there February 2-4 and all expo information can be found here: http://www.newenglandgrows.org/

Hope to see you there!

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Quote of the day

“You must make architecture that respects nature’s resources and does not look like your ego poking the landscape” – Javier Barba

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Aiming for Hardscape Success

HGTV recently featured an article that featured a handful of landscape designers sharing tips for design of outdoor spaces. We found this article full of good advice for anyone planning a hardscape.

The major points of the article as we see it are: planning, overall design and style, scale and structural integrity.

The resonating theme of the article and one that we see on a regular basis is planning. The biggest challenges in landscape and hardscape design usually arise from lack of planning. Careful research and planning of everything from overall design to building materials is crucial to achieve a desirable outcome.

Planning the whole space before the start of any project is again of the utmost importance. Even if the project is phased over a few years, it is very important to consider the whole landscape area no matter how small the current project being undertaken is. The article recommends planning a design for the whole area or consulting a professional to create a design for the entire space.

In all hardscape or landscape projects, consideration should be given to scale and natural curves and shapes of the space so that various elements fit in with the rest of the landscape.

Planning the whole design also enables the project owner to emerge with a specific style instead of mixing and matching something that could potentially clash.

The article offers and we wholeheartedly agree that no homeowner (who is not a structural engineer that is) should undertake a structural project or a significant size wall without consulting the proper engineering professional. Potential damage and even injury can be prevented with a simple engineer review and consult.

Following the relevant standards such as having the correct amount of base material that is properly compacted as well proper grades, levels and depths is of significant importance for a lasting hardscape project.

A recently completed successful NSWS™ project:                                                                 (Design by Weinmayr Associates and landscaping by Old Village Landscape)

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