August 17, 2018

Do I really need a permit?


Are you thinking of building an Allan Block retaining wall, fence, or courtyard patio? If so, you may be wondering “Do I need a building permit to do this job?” or “How tall can I build this wall before I need a permit?” You are not alone. This is a very common question when it comes to building patios, fences, and retaining walls.

Unfortunately, there is no one simple answer to either of these questions. Every state, city, county, and municipality is varied in what they require a building permit for. Below is an excerpt from the City of Saint Paul on what they require a building permit for. As you can see the city requires a permit for any fence application. When building a retaining wall over four feet tall a building permit is required. A simple Google search ought to turn up similar documents for your local city. You can’t find your local permit requirements via the internet? Try calling your local city offices. Ask to speak to somebody in the Department of Safety and Inspections. Somebody in their office should be able to provide you with your local permit requirements for any and all applications.

Once you’ve sorted out whether or not you need a permit, you might want to consider hiring an AB Certified Contractor. Our Certified Contractors are well versed in how to install all of our AB Products. They are well versed in both our Best Practices and Commercial Installation Manual. This will ensure whether you’re building an AB Fence, Courtyard, or Retaining Wall project it will stand the test of time for many years.

August 16, 2018

Best Practices for Zero Retaining Wall Failures - Below Grade Water Management


When more than incidental groundwater is known to move through the retained soils, extra precautions need to be taken with your retaining wall project.

The wall rock should be placed to the limits of the geogrid lengths up to a height equal to 12 inches (30 cm) higher than any water source.  This is typically done using a blanket drain, which must be at least 6 inches (15 cm) thick.  (ref. BP, Chapter 5.1)

Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry.  To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.

August 14, 2018

Best Practices for Zero Retaining Wall Failures - Heel Drain Recommendations


In retaining wall applications where water is a large concern, a heel drain is often incorporated.  The purpose of the heel drain is to pick up any water that migrates from behind the retaining wall structure at the cut, then route the water away from the reinforced mass.

Similar to the toe drain, the pipe may be a rigid pipe with holes at the bottom or a corrugated perforated flexible pipe.

The heel drain should be vented at 100 ft (30 m) intervals along the entire length of the wall and should not be tied into the toe drain system.

For infill soils with a high percentage of sand and/or gravel the heel drain pipe does not need to be surrounded by wall rock.  (ref. BP, Chapter 4.2)

Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry.  To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.

August 10, 2018

How to Build a Retaining Wall that Runs into the Slope at its Base

Stepping Up the Base

So you’re building a retaining wall with Allan Block and the base of your wall runs into a slope. What do you do? The answer is simple. Step up the base. When building step-ups, begin the base course at the lowest wall elevation. When building step-ups, begin the base course at the lowest wall elevation.

Dig a base trench that is 24 in. (600 mm) wide. The depth of the trench is determined by allowing for 6 in. (150 mm) plus an additional 1 in. (25mm) for each 1 ft. (300 mm) of wall height for the amount or buried block that is needed. The trench also needs to extend into the slope far enough to bury one full block. If a slope is present below the wall, contact a local engineer for assistance.

Compact and level the base trench making a minimum of two passes with a plate compactor. Place the drain pipe at the lowest possible point toward the back of the trench. Place a minimum of 6 in. (150 mm) of wall rock in the base trench and check for level. Compact the base material, making a minimum of two passes with a plate compactor.

Excavate the second step up making sure to accommodate for the base material and buried block. Compact and level the step-up area. Place the base course of blocks on the base material and check for level. Fill the hollow cores and 12 in. (300 mm) behind the block as well as the base area of the next step up with wall rock then backfill with infill or approved on-site soils. Make sure that the blocks and the base of the next step-up are level. Compact the wall rock directly behind the block and the next step-up area a minimum of two passes with a plate compactor. Repeat these steps to the top of the grade. Keep in mind the block at each step-up must be completely buried to maintain the proper base depth and to prevent wall failure due to erosion.

For more installation tips, visit allanblock.com




August 9, 2018

Best Practices for Zero Retaining Wall Failures - Alternate Drain Locations


Sometimes the drain pipe behind your retaining wall must be raised to accommodate outlets through the wall face.  A shelf of low permeable granular soils, level with finished grade should then be created to prevent water from ponding below grade. See Allan Block Design Detail #4 – Alternate Drain, in the Allan Block Spec Book.

Drain pipes existing to daylight through the wall should be installed with rodent screen to prevent nesting within the pipe. Blocks can be cut to allow for installation of a manufactured drain cover, or Wall Drain Pro could be used without the requirement of cutting block. (ref. BP, Chapter 4.1) 

Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry.  To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.