Collapse Search and Rescue Operation: Tactics and Procedures
Part 13: The Split Sole Raker Shore
BY JOHN P. O`CONNELL
Generally, the split sole raker shore is used when there are open soil conditions around a structure; these conditions are most commonly found around private homes. The main differences between this type of raker shore and the solid sole raker shore are in the positioning of the bottom of the rake and in the construction of the bottom braces. Instead of resting on the sole plate, the base of the raker is embedded in the ground, generally wedged into some type of blocking. Instead of a one-piece bottom brace on which the rake bears, the brace used in a split sole raker shore consists of two pieces that are anchored alongside the rake at the lowest point possible.
The split sole raker can be either erected in place or preerected in a safe zone outside the collapse area. For safety reasons, preerecting is preferable, particularly when wall stability is in doubt, which most likely is the case in these operations.
ERECTING THE SPLIT SOLE RAKER
l. Determine the height at which the rake will intersect with the damaged wall. This will tell you the angle you can use with the size lumber available. If, for example, the height of the rake is to be 12 feet up the face of the wall and the length of the material you are using is 16 feet long, a 54- or 60-degree angle would be most effective. If a 45-degree angle were used, the rake would have to be 17 feet long, one foot longer than your material, meaning that the height of the rake would be six inches short of your mark. While this length generally is more than sufficient–it is well within the support-point range–using a 54-degree angle would be more effective. This angle would give you a rake 15 feet long at the 12-foot wall height. The 60-degree angle also can be used; it would give you a rake length of approximately 14 feet. For strength and stability, a 60-degree-angle rake should be the maximum angle used in collapse shoring operations. Always take full advantage of the available lumber lengths for your rakes to maximize strength.
2. Lay out the location for the base of the rake. One method for determining where the base of the rake should go is to transfer the angle to be used into the “pitch” on the steel square. If, for example, the angle is 45 degrees, the pitch would be 12/12; it would be 9/12 for the 54-degree angle and 7/12 for the 60-degree angle–the angle we will be using as an example in this article. What this means to firefighters erecting the shore is that for every foot of wall height the shore will cover, the raker will extend seven inches from that wall. This means that if the height of the raker on the wall is 10 feet, the distance away from the wall at the base would be 70 inches. (See illustration, p. 95.)
This is the distance away from the wall at which you will start digging the hole that will hold the raker shore. The hole should be approximately 12 inches deep (roughly the depth of your shovel blade) and on an angle to match the square end of your rake.
If you are working in soft ground, make the hole roughly two feet wide and lay in two blocks; nail a piece of plywood to the blocks to make one pad, and wedge it under the rake to help transfer the load over a wider surface, providing better bearing strength. If you are working in hard ground, in which the soil is more stable, you will have to dig only the width of one block. Place the wedge under the rake and tighten at the appropriate time. (See photo above, left.)
3. While this operation is underway, have another team cut the angle on the rake and then cut the rake to the predetermined length.
4. Nail the top cleat to the wall plate at the height at which you want the raker to intersect the damaged wall.
5. Nail the rake into the wall plate directly under the top cleat. Make sure the fit is correct.
6. Nail the gusset plate to the wall plate and rake with the proper number of nails.
7. Temporarily nail down one of the bottom braces to the wall plate and rake to keep the shore together as it is installed. Keep it as close to the bottom of the shore as possible. (See photo p. 96, right.)
8. Place the raker shore up against the wall and lower it into the hole the other team has prepared.
9. Anchor the shore into the wall, and snug your wedges into position.
10. Finish installing the bottom braces, one on each side of the rake, as close to the ground as possible. (Left, top photo.)
11. Place a filler block in the space, to help stop any deflection of the bottom braces, which may weaken the shore. (Left, second photo.)
12. Tighten up the wedges at this point and tack in place.
13. Install the diagonal brace, just above the bottom braces and up to the rake, on both sides. (Left, third and fourth photos.)
The shore is completed. (Below, right.)
LAYING OUT THE 60-DEGREE RAKE ANGLE
Following are two methods for laying out the rake for use with the elevated angle of 60 degrees–the highest angle that can safely be used by rescue personnel. Constraints of materials or the space available may necessitate the use of this steeper angle.
The steel-framing square.This is the most accurate method of determining the proper angles. The “pitch” on the square will be 7/12 for the 60- and 30-degree angles (see Part 12 in the November 1994 issue of Fire Engineering). By holding the tongue of the square on the numbers “7” and “12” on the blade along the bottom of the lumber you are using, you will be able to get both angle marks. Holding the square in the same hand and standing on the same side of the lumber at all times (this helps you stay oriented and is less confusing), scribe a line along the blade from the top of the lumber across to the number “12”; then cut your return notch to accept your wall cleat. This will give you the 30-degree angle that will be placed on the face of the wall plate at the height you have determined your shoring will be accepting the weight of the building. In this case, the angle off the ground against the building will be 60 degrees.
Now, measure back 14 inches per foot of wall height to determine the rake length. Add an additional foot in length–the usual depth of the hole dug in the ground. You now have the proper length of the rake. As an example: If the wall height is 10 feet, measure 10 ¥ 14 inches, giving you 140 inches; then add 12 inches to the overall length, making it 152 inches. This will be the length of the rake shore. At this point, cut the rake square, and wedge it into the ground on an angle, completing the erection of the shore. The position of the square will be the same for any size lumber since the angle does not change–only the width of the material being used.
The layout method. This method is not as accurate as the steel-square method, but it will work if no square is available. To get the 30-degree angle that will be placed against the face of the wall plate–thus giving you a rake shore of 60 degrees off the ground –all you need is a tape measure. Make sure you are working off a square end of the lumber; otherwise the angle will be inaccurate and the shore will not assemble properly. On a 4 ¥ 4 rake, the most common type used, measure back one side from a square end six inches. Then scribe a diagonal line back to the (opposite) end and cut. With a chain saw or a 1014-inch circular saw, measure back along the face of the cuts until you have 112 inches at right angles to the first cut. Then make the cut and measure back from that point to determine the overall length of the rake, as described above. (See illustration above.)
IMPORTANT NOTE WITH ANGLES GREATER THAN 54 DEGREES
Rake shores with an angle greater than 54 degrees must have additional wall-plate stabilization due to the increased upward pressure applied to the raker shore. You can stabilize the plate in two ways. Method one, generally the easiest and fastest, is to increase the length of the top cleat by one foot; this will make the top cleat three feet long. Follow the same nail pattern, increasing the number of nails on a 4 ¥ 4 raker from 16 to 24. On a 6 ¥ 6 raker, increase the nails from 24 to 36. The additional nails will stop the increased upward forces from adversely affecting the raker shore. (Top right photo.)
Method 2, which is much more time-consuming but also effective, is to notch the wall plate and then install a normal two-foot cleat. This can be accomplished with a circular saw set at a one-inch depth and cutting approximately one-inch-wide cuts through the width of the lumber. (Top left photo.) The length of the cuts will vary according to the thickness of the rake pieces. For a 4 ¥ 4 rake, the cut will be twice the nominal thickness of the lumber, or eight inches (or about nine one-inch-wide cuts with the saw); for a 6 ¥ 6, the cut will be 12 inches. This will give you sufficient room to set the rake into the notch. After you have cut the one-inch-wide “kerfs,” they can be cleaned out with the back of a straight claw hammer. Make sure all the cut material is cleaned out or the rake will not fit properly. (Bottom left photo.)
After the notch has been completed and sufficiently cleaned out, install the normal two-foot-long top cleat. (Bottom right photo.)
One of these two methods must be used when erecting shoring greater than 54 degrees, or the shoring may not hold properly.
HORIZONTAL BRACING
Each raker shore erected against a building operates independently of the other, as the shores are supporting only the weight of the areas with which they are in contact and a small zone around the raker itself. When a series of raker shores is erected, they should be tied together to create a rake system.
Horizontal bracing includes “longitudinal” bracing, “X” bracing, and “V” (or “A”) bracing. Adding horizontal bracing helps counteract any lateral forces that can be applied to the raker shores, which can diminish their efficiency. When a whole series of raker shores are braced horizontally, they can withstand large amounts of stress from several directions. In an earthquake situation, they will be able to withstand aftershocks more readily. The braces should be constructed of 2 ¥ 4 or 2 ¥ 6 (which is preferred, if available) material.
Begin bracing by nailing three longitudinal members to the raker shores–at the bottom, at the center over the diagonal braces, and near the top–keeping them parallel to each other. It is also more effective to overlap the longitudinal legs than to try to splice them on a rake; they will be stronger by fully contacting the raker shore. (Right, top photo.)
Two or more rakers require “X” bracing (in addition to longitudinal bracing) to create greater lateral stability and effectiveness. (Right, second photo.)
For a series of rakers, double “X” brace the first two and last two rakers. Place the first cross member of each “X” brace directly onto the raker, butting up to (flush to) the longitudinal bracing. The top cross member of each “X” brace then is nailed to the top of the longitudinal members, as shown. (See illustration.)
For a long series of raker shores, place an additional brace in the center, in the form of a “V” or “A”–it does not have to be an “X” brace to be effective. (Right, bottom photo.)
Any series of raker shores, whether solid sole or split sole, must be horizontally braced for full safety and effectiveness. n
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JOHN P. O`CONNELL has been a firefighter with the City of New York (NY) Fire Department for 15 years and, as a member of Rescue Company 3 in the Bronx, has more than seven years of collapse rescue experience. He is an instructor of shoring and building collapse at FDNY`s Training Academy and has been involved in the writing and teaching of the department`s collapse and shoring training curriculum. O`Connell is a member of New York Task Force 1 of FEMA`s urban search and rescue network and is a rescue specialist instructor for FEMA. He is a New York state-certified fire instructor and spent more than 10 years in the building construction industry.
