"Landscaping" Retaining Wall- Frost Depth?

[MJB315]

All,

We are replacing a small (18" tall) retaining wall for a Client and are wondering if it is required to sink the footing to the frost line (48"). The wall is about 10' long and simply retains soil along an exterior walk way.

Our initial instinct is to design a standard cantilevered retaining wall down to the frost line, but are looking for alternatives. Has anyone used a less stringent detail? Is there an IBC 2009 provision that requires that retaining walls (of this size and purpose) to be supported down past frost?

"We shape our buildings; thereafter they shape us." -WSC

 

[MiketheEngineer]

What about Versa-L ok or equal. Their specs and details show no deep footings. The wall just moves around a bit as needed.

I installed my own - so you know any idiot can do it.

I would be worried about a poured wall - cracks, etc.

After 5 years - still looks good.

Cost is about the same all thing considered and I think they look much better.

 

[SteelPE]

Section 1809.5 of IBC 2009 deals with frost depth and leaves most of the requirements up to the local jurisdiction. You may want to look in this section to see if you can work your way out of the requirements for a landscaping retaining wall (it’s up to your interpretation).

As far as other types of walls, see the post above.

 

[woodman88]

The building department may have allowable retaining wall details for such a small one. Check with them.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[jbuening]

It is my understanding that if you use a segmental block (landscaping block) wall that it does not need to go down to frost level. They are essentially a gravity wall and the blocks move and articulate with frost heave. If you go with a concrete or CMU wall, then go down to frost level. This all assumes the local code doesn't cover landscaping walls. Our local code has height restrictions, in which once you reach a certain height of landscaping wall it would need designed. With your height, you are looking at around 2-3 courses high...not much to even heave in my opinion.

 

[concretemasonry]

Our local municipalities and counties have oftem uniform standard design plates for lower walls that are available and based on the major retaining wall systems (SRWs) and their own crews use them on projects such as street widening,, new sidewalks, etc. Very similar to the assistance given by building code offices in CA for 6' privacy walls.

None of the major wall systems will suggest the use of a concrete footing or guarantee anything since it is a flexible wall. - Not unlike the dissimilarities between concrete pavements (rigid) and asphalt or paver streets/roads (flexible).

Dick



Engineer and international traveler interested in construction techniques, problems and proper design.

 

[dhengr]

The above doesn’t suggest that you shouldn’t detail properly by grading for proper drainage; maybe a means of drainage behind and under the wall, to daylight if possible; and a proper gravel base/footing/drainage. You have a couple courses below grade, on the gravel footing, and some topping material to drain water away from the footing excavation. All in an effort to minimize frost heaving potential. Much higher than that and you may need a handrail, you may want to check that out.

 

[MiketheEngineer]

In my town - you can go to 4' w/o permit or handrail.

But I agree that a handrail at 4' would seem prudent

 

[concretemasonry]

dhenge -

The standard detail and instructions for all the major products do have detailed instructions and suggestions on drainage systems for behind the wall. Unfortunately, for the minor small 2' high walls, they are not always followed.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[BAretired]

I wouldn't extend the footing down to frost level. Top of footing can be 6 or 8 inches below grade to allow for landscaping. If it heaves, so what? So does the exterior walkway. Just make sure you don't tie it in with anything which won't heave.

BA

 

[jbuening]

Exactly. Many of the block manufacturers have standard details on their websites that you can use and refer to. One example would be Anchorwall.

http://anchorwall.com/cmsVirtualUserfiles/TechMatl/CAD/Diamond-Section-Grid-Sidewalk.pdf

http://anchorwall.com/exploration/p...ning-Wall-System-Straight-Face&s=cad-drawings

 

[ACtrafficengr]

Last year, we took out a cast-in place wall about 18" high, with about the same depth below ground and no footing. It had been there for decades and decades without problems.

Funny story - a cemetary (is) on the high side of the wall. While excavating for a new sidewalk, the wall slipped into the excavation. There was an archeologist on site due to the cemetary, and she nearly had caniptions when she saw wood fragments embedded behind where the wall had been. It took a while to get her calmed down enough to realize it was the remnants of formwork for the wall, not caskets!

We replaced it with segmental block.

Maybe the tyranny of Murphy is the penalty for hubris. -

http://xkcd.com/319/