How To: Ledge Repair
When the skatepark in the City of Seatac, Washington, was opened, the designer didn’t plan for the popularity of a small ledge built into a larger pyramid structure. Over the next five years the ledge was ground down until it was rough and pebbly. With an upcoming contest, Dave Waite and Jake Weger of Tacoma contacted SPS NW Regional Director Brock McNally about repairing the ledge. Here’s how you can do the same thing at your favorite skatepark.
As you’ll see here, ledge repair (just like any DIY project) is mostly preparation. Actually doing the work is relatively quick, especially if you’ve planned everything out correctly.
Step One: Plan It Out
The ledge repair is simple enough for anyone to do with the right resources. Take a look at the problem ledge. The offending edge should be cut out of the larger form then a new piece dropped in. For this exercise we’ll be replacing the worn-out concrete ledge with granite since it lasts longer, rides better, and looks better than other appropriate materials.
The procedure here will require the use of anchor pins to keep the new granite block from sliding off its bed laterally. The sheer weight of the granite block combined with the adhesive qualities of the grout would probably be enough to prevent it but the ledge is very popular and there was very little interest in doing this more than once, so anchor pins are included in this design but you may want to skip them in your ledge repair project.
Step Two: Gather Materials
This is a pretty simple job but will require at least two professional services. The granite needs to be ordered and shaped to fit perfectly, and a special saw will need to be used to cut out the worn-out area. Beyond that the materials and tools are simple.
Rotohammer (for drilling into the concrete and granite; rent it)
- ¾-inch bit
Chalk line (for snapping straight lines)
Small prybar (2 is better)
Garden hose (if on-site water is available)
5-gallon bucket (you’ll need several if no flowing water is nearby)
Big, cheap brush
Black marker (Sharpie)
A friend or two
Granite Brick (see below)
55-pound bag of high-strength, non-shrinking grout
Big fat washers (for supporting the granite brick)
2 pieces of 6-inch long rebar
Various chunks of 2×4
20 gallons of water (if no on-site water is available)
Most of the materials you can get at any hardware store. The rebar can be scrounged and cut with a hacksaw or you can buy it. Some places will cut rebar down for you but you’ll probably end up with a lot left over.
Step Three: Order Granite
The ledge at Seatac is 8-feet long. The salt-and-pepper granite was ordered from a local quarry. You’ll want to request a smooth but unpolished finish. The leading edge—the edge that people will be grinding on—will need to be a little bit round. If you don’t request this rounded edge, the first time someone hits it hard it will blow out a chip of granite and you will have wasted hundreds of dollars. A half-inch rounded edge is good.
The brick itself should be wide enough for tails and noses to be completely on, and deep enough so that a skateboard’s wheels are only in contact with granite when the board is locked into a slide. In other words, the brick should be 6-inches wide, 4-inches tall, and as long as the pad that it’s going into. For this 8-foot ledge the granite brick cost $600.
Since it only weighed about 200 pounds, it was easy to pick up rather than paying for delivery. If your project requires a longer span than 8 feet, you may want to consider using two identical pieces.
The granite order should take a few weeks to fulfill so shop around early and get this part started. (You can always store the granite in your back yard until you’re ready to use it.)
Step Four: Schedule Concrete Sawcut
This is the only professional service that will require specific scheduling so you’ll need to pick a day that you know everyone will be available. When you talk with the concrete sawcutting service you will want to communicate your specific needs so they can bid on the project accurately and bring the proper tools. Repairing a ledge is not a big project for most companies that perform this service so don’t be surprised if you don’t get a lot of enthusiasm from them. If you explain that you’re performing a community service and are unpaid, it may earn you some interest.
You will be asking for two cuts. One will be a long vertical cut about 6-1/2 inches behind the existing leading edge. The second cut will be a lateral cut into the front face of the ledge about 4-1/2 inches from the top of the ledge. The desired result is that a long rectangular strip of concrete will be removed from the existing ledge. It will help to have all of the ledge’s dimensions available when you’re talking with them in case there are questions.
The concrete sawcutting service should cost around $300 and take 2 hours or so.
Step Five: Stage Up
The days leading up to the construction date are important to go over your materials and tools list again to ensure you won’t need to be making runs to the hardware store every hour. Check your materials then double-check.
Head down to the site and make sure no late-breaking developments will disrupt your plans.
Talk with the Parks Department or whoever manages the area around the ledge to see if water is available. In some places the Parks Department may need to use a special key to turn on a water spigot. If you can borrow this key or have a Parks person meet you, it will save you a lot of headache. (If water is not available, three or four 5-gallon jugs should be enough.)
Step Six: Prep the Site
Arrive early on construction day and clean up. Try to sweep the whole area since you will be taking pictures and want the space to look good. Especially pick up anything bright, like empty water bottles and food wrappers. You’ll probably use these photos to promote your next project.
Take special care to clean up around the ledge itself.
It will help to have at least one other person with your in case you need to leave for some reason. You won’t want to pack up all the tools and materials every time you need to run to the store or use the restroom. Having a second person will make porting the materials (especially the granite) go easily.
Move your tools and materials near the ledge. The concrete sawcutter will be spewing water all over the place so keep those things that shouldn’t get wet away from the working area.
Take your “before” picture now.
Step Seven: Chalk and Cut
Measure out where you want the cuts and stretch the chalk string along the length. You’ll probably need a second person for this. Pull the string tight and twang the string against the concrete ledge. It should leave a nice straight line showing where you want the cuts. Spray the chalk line with varnish so that it won’t rinse away.
If you don’t have a chalk string, a black marker can work. Don’t make the line so thick that it’s difficult to tell where exactly to cut, but DO make it thick enough to see even when there’s water splashing over it.
The concrete cutting should take an hour or two. When it’s all finished the worn-out portion of the ledge be removed easily. Take that piece out. It’s garbage (unless you want a 200-pound piece of memorabilia).
Take pictures while you wait.
The concrete cutter will pack up and leave.
Step Eight: Drill Anchor Holes (Optional: Recommended)
Rinse the entire area. The concrete cutter will leave gray slurry all over the place. It’s good to have most of this cleaned so that when it dries the dust doesn’t affect the grout.
Bring the granite block over and gently test-fit it into the gap. Be careful when you move it as the granite is strong but will not take shocks well. If it breaks you’ll become very cross and it will cast a shadow over the day.
Rest the granite on a few of the 2-by-4s you’ve brought with you. They’re soft and will help protect the brick from shocks. Put it next to the gap upside down so you can easily visualize how the matching pins holes will line up.
You are going to be drilling holes for the two anchor pins. You will need two holes (one for each anchor) in the underside of the granite and two matching holes in the cut-out area of the ledge. These holes will need to match up perfectly so don’t do any drilling until you’re confident that the measurements are right and that you’ve taken everything into consideration.
For an 8-foot ledge the anchors should be 2-feet in from each end or, in other words, you should have an anchor hold at 2-feet and at 6-feet.
Do not take your measurements from the back edge of the cut-out area or the back of the granite brick. Only take your measurements from the top or front (face) of the ledge. The reason is that you will be “floating” the granite on a bed of grout which may not create an exact measurement. You know that you want the face of the granite to be aligned perfectly to the face of the ledge, and that the top of the granite will be aligned perfectly with the top of the ledge, so measure the same distances from these sides. (You don’t know exactly how thick the grout will need to be to bring the brick into perfect alignment so that’s why you should use the sides you know are aligned as your measuring standard.)
The anchor holes should be centered on the brick or 3-inches in from the sides. Put a small mark where you’ll be drilling into the granite. Grab your drill and go to work. You may want to use a piece of tape or your marker to indicate the desired depth on your drill bit so that you don’t drill completely through the granite block. Simply measure three inches from the tip of the bit. When you drill down to that point, stop.
Drill your anchor pin holes into the granite now.
On the ledge you’ll measure 2-feet in from the sides and 3-inches from the front and put a small mark where you’ll be drilling into the concrete.
These black marks should match up if you were flip the granite into its final place. If you’re unsure, gently put the granite into place (on some pieces of wood) with the rounded edge facing out correctly. Did you put the marks in the right place? Good. You won’t want to screw this part up.
Here you go! Put on your eye protection just like Brock here and drill the matching two anchor holes into the concrete now.
When you’re done, close your eyes and blow into each hole to clear as much of the debris out of there that you can.
Step Nine: Set Anchor Pins
Load up the caulking gun with the adhesive, cut off the tip of the adhesive tube and give it a test squirt. Now grab those small bits of rebar and give a generous squirt of adhesive into one of the granite holes.
Push one of the rebar anchor pins all the way into the hole. You should have about 3 inches of rebar sticking straight up.
Now do the other granite hole.
Don’t dilly-dally between squirting the adhesive and putting in the pin. The stuff dries quickly.
Take some pictures while you wait for those pins to set up nice and firm.
Step Ten: Set Risers
Grab some of those washers and make a stack about a ½-inch tall (maybe three or four of them). Put a stack next to each anchor hole on the ledge and one in the middle of the area. It doesn’t need to be exact. These washers will hold up the whole granite block while the grout dries. Without these risers, when you put your wet grout down, the weight of the granite will squish it and the whole thing will sink and maybe even rest on the ends of the rebar anchor pins. That’s not good. You want the weight of the granite to be resting evenly across a nice bed of grout…so the risers will keep the block in place until the grout is dry.
You may want to tape the small stacks together so they don’t fall apart while you’re fiddling with the heavy granite block. The tape won’t hurt anything and the washers are ultimately going to be buried in the grout like a time machine, so no worries if it’s ugly.
Take a picture.
Step Eleven: Test Fit
Gently set the granite block with the anchor pins down onto the cut-out portion of the ledge. Naturally, the pins fall perfectly into the holes in the concrete. The washers should hold the block up so that the block is aligned with the top of the ledge. If it’s too low, add another washer to each stack. If it’s too high, remove a washer.
For confirmation you should also check the face alignment. There should be enough play in the anchor pins to move the block slightly forward or backward until the face of the block aligns with the face of the ledge. If not, grab your drill and widen those holes in the appropriate direction.
Don’t forget to check your lateral alignment. Either end of the block should be aligned to the ends of the ledge.
A good way to make small adjustments to the heavy block is to slip a prybar in the crack created by the washers and gently lift the block into the desired position. We don’t recommend using your fingers for this step.
If everything looks great and according to plan, return the granite block upside down on its wooden blocks near the cut-out.
This concludes the preparation. It’s all construction from here. Let’s finish this.
Step Twelve: Grout
Take the brush with some clear water and get the whole cut-out area of the ledge wet. This will clear out any dirt and help the grout soak into the concrete and build a stronger bond.
Take one of those buckets and dump most of the grout and with water. Mix it all up until it has the consistency of thick, goopy putty. If you have a mixer attachment for your drill, this is a great time to use it.
The recipe should be on the bag and you can add grout to thicken or water to thin the mixture. Too much water will reduce the strength of the grout, but if it’s too thick it will dry quickly and be difficult to work with.
With your mason’s trowel, glop a generous amount of grout along the back corner of the cut-out area. More is better than less. Avoid the anchor holes as you will be squirting adhesive into them.
Don’t use all of your grout in this step if you can help it. You’ll need more to fill in around all the spaces in a few minutes.
Squirt some adhesive into the anchor holes. Fill the hole all the way up. It will squish out between the granite and the concrete when you lower the brick pins into the holes.
Try not to cover the riser washers with grout.
Don’t fool around while doing this step. The grout will begin to dry pretty quickly so you only have 10 minutes or so to get all the grout put down. If you are prepared, it should go really quickly.
Lift and gently rest the granite block into place with the pins down. The grout should ooze out of some areas. Wherever the grout is oozed out, scrape it off with your trowel and push it with the trowel or your fingers into areas where there are gaps. Just squish it on in there. Use the prybars to slide the block so that the sides of the granite are in alignment with the sides of the concrete.
After 10 minutes or so and the grout is nice and firm, you can take your thumb and make the seam nice and smooth. It may help to splash a little water on it to moisten it a little…just don’t go crazy or you could push water down into small cracks and weaken the bond.
Take a picture.
Scrub off whatever small bits of grit are left over with water and a brush or broom.
Step Thirteen: Clean Up and Skate!
You can begin rinsing and sweeping the area. Try to keep water off the drying grout. You should give the structure about three hours to dry completely before using it. After a few hours you should be able to jump on it, grind it, and anything else. It should be strong as an ox and last for years. When the grout has all turned a light, dry color it’s usually pretty close.