Control joint detail for a limestone block retaining wall 1

[kww2008]

Could someone show me a typical detail for control joints for a long gravity limestone block retaining wall?. The wall is three-block height, The first layer above ground has 3 blocks, second layer 2 and the last layer 1. The front face of the wall is vertical.

 

[oldestguy]

Why control joints for a structure loaded with joints?

 

[kww2008]

The limestone blocks are laid out in a stretcher bond pattern, a pattern common in brickwork. The control joints are to be provided to control the locations where cracking occurs. If they are not provided, cracking is likely to occur randomly along lines of mortar joint (as they are the line of weakness) and that will be unsightly. My query is whether someone can show or describe to me what a typical control joint look like.

I have been thinking more about this, and wonder if such a joint would just be a mortar-filled joint through the wall with sealant provided in the gap along the expose face lines. This will create a line of weakness through the wall for cracking to occur and is easy to build (as compared with having a compressible filler placed in a through joint) since any compressive filler will have to shape like the wall which has three different thicknesses over its depth).

 

[oldestguy]

Perhaps explain the use and the rough size of the blocks. Is this wall then to be plastered in some manner? Normally an exterior gravity retaining wall made up of masonry units or stone does not need any control joints. With the depth of this gravity wall, from face to interior, it won't change in temperature enough to cause dimensional changes of importance. Do an Internet Google search of various suppliers of wall units and I would not expect to see any comments about control joints.

 

[oldestguy]

One more. For the common gravity wall made of "blocks", no mortar or joint material is used. We don't worry about "cracking" since all the joints can move if needed. No special drain holes are needed.

 

[kww2008]

This is not a low garden wall and can be quite high. Joints are mortared. Just found a website with suggestions as to where to place control joints for these types of limestone walls. However,the detail of the joints has not been not provided.

http://www.jaffalimestone.com.au/guides

 

[oldestguy]

A confusion of terms is present here. For the wall you apparently are planning, the use of the term "limestone" in the USA would imply stone cut from a quarry, with rough sides. For that usage and as a retaining wall, no mortared joints are used. For a masonry block wall, your "reconstituted limestone", which, for me, is an entirely different wall material maybe use mortar. For the masonry wall the change in temperature of the wall would be affected by the "heat sink" effect of those blocks farther back from the face. That makes the change in dimensions of the face less likely. That,then, would call for a longer spacing of control joints than for a single block depth (front to back). Masonry walls in a building typically require a joint spacing for temperature effect between 15 and 30 feet, averaging at 20 feet. An earth retaining wall has much less effect of temperature change in the area. Thus, for your wall, I'd set that spacing at 30 feet or more. roughly 10 meters. This is similar to AASHTO specs for cantilever and gravity retaining walls. However, if no mortar is used, I'd omit the control joints for the same reason given in my first post.