Concrete Step Treads

I went looking for information on how to make steps but couldn’t find any. A few videos that were close but not good enough.

Making concrete steps is easy and heaps cheaper. I’m making a step for about $15-20aud per tread instead of $75-$100. The results were really good. Takes a bit of time to set up the mold but once that is done, it’s robotic. Takes about an hour to make each step from scratch. That doesn’t include time waiting for concrete to bang off, just time actually making one from welding steel to finishing the concrete.

Commercially produced steps use a variety of techniques including pressure and pre tensioned wires. None of which is practical at home or covered by this instructable. Steps that are 50mm thick (min residential thickness) are possible using these techniques. Industry standard calls for 30mm concrete cover over steel without these techniques. Using 12mm rebar with 30mm cover gives a step 72mm but pressure and pre tension allow for thinner steps. Please check local building codes if requiring a certified product and construct accordingly. The process will remain the same just different measurements.

Note that commercial steps need to be 70mm. I chose to go 60mm steps using 12mm rebar instead of going smaller steel for two reason: 1. I already had it 2. 12mm is stronger than 6 or 8mm and it’s for residential. The loss of concrete coverage isn’t that concerning for me.

I used two different concrete mixes but found the Maxpro concrete 50mpa mix with more fines gave a better finish. Plus it contains fibre to reduce cracking.

There was a comment received below about additives to waterproof the steps. I did not add anything to my steps and cannot provide any advice on the matter. Caution must be taken when adding anything to concrete as it may have a negative effect. Consult an expert or read product instructions carefully before adding anything. If waterproofing is an issue you can always apply a sealer once steps are cured or even paint them for added protection.

What I realised is that there are no real tricks to forming steps, just the process. So hopefully this will give you the confidence to give it a go.

Tools:

-wood working tools such as saws, drills, impact drivers, squares, clamps and straight edges.

-metal working gear such as grinder, welder and safety gear, wire brushes.

-concrete tools. Something to vibrate the concrete. I used a pneumatic chisel and an orbital sander with a plastic lid fitted to protect the base. Float. I just made a small float by rounding edges on a piece of ply to smooth the concrete (Maggie float) and a small steel trowel for finishing

Molds: Form ply, screws and material for texture. I used plastic as per above pic that was free from Bunnings. Go to the paver section and find plastic between the pavers. It’s just thrown out!

Miscellaneous items such a plastic, silicone spray, water bottles for measuring water, items to mix concrete like mixer or round tub etc

Step: concrete- I chose 50mpa and fibre reinforced bags, re bar and nuts and bolts to bolt steps to stringers.

Without a good mold, you won’t get the consistency and professional look. Spend extra time on the molds. An extra hour working on a mold is better than spending an hour on every step you make fixing them up.

I needed a step that was 1000mm long and 240mm wide. Standard sizing is 920x240mm

The process for building the mold is very simple. Build a box with the internal dimensions matching the step you need. I chose to have a piece of ply on the bottom of my mold. If you were placing your mold on the table or floor you could get away without it but I wanted the option of being able to move wet steps.

I used only screws for my build and no glue. This allows me to remove a couple of screws when removing the step to assist with easy de molding.

Prior to screwing it all together, take the base and place it on top of the materiel you intend to use for your tread texture. Cut around the base for a perfect fit.

I used m8 galvanised bolts and locating holes in the mold to locate the reinforcing jigs in place.

Once the jig has been constructed, take 2 pieces of ply that are at least the outside width of your mold. Position under the the bolt locating holes of the jig board. Drill holes using an 8.5mm bit. It doesn’t really matter where the holes end up as long as there is enough ply either side so it still overhangs the edge of the mold. These two pieces are used to locate the welded reinforcing in the mold (reinforcing jig). After a welded piece of reinforcing has been completed, place the bolts into the drilled holes of the ply jig and attach some nuts. Place into the mold and position. Drill a hole through the ply into the mold. Use a bolt to lock the ply to the mold.

Hint: if making multiple molds, use one reinforcing jig piece as the drilling template for all the others so that it doesn’t matter which mold they are used on. Otherwise you waste a lot of time figuring our which piece goes where.

I also found that the middle of the mold tended to bow out if a center brace wasn’t used.

The jig allows for quick construction of the reinforcing and bolts. I needed to construct a lot of steps that were being bolted to prefabricated stringers. Accuracy was important. Results would have been all over the place or very time consuming without a jig. If you are only making 2 or 3 it’s probably not worth the effort, but more than that, for sure. I used one edge of the jig as a reference and took all measurements from that instead of trying to center and square everything. It was quicker and a mm here and there wasn’t a big deal.

The jig consists of the main jig board that has four locating holes for the bolts and two rebar locators with two slots to locate the rebar and bolts.

Cut a piece of ply big enough to do the job. If you are using a base in your mold, cut an extra one the same dimensions and use that. It makes all the measurements so much easier. Everything just looks right.

For the jig, take 2 strips of ply about the 300 long and 30mm wide lamp together on the long edge. Determine if 30mm lateral cover ie the rebar in 30mm from the long edge, is going to interfere with the the positioning of the mounting bolts. Depending on this will change the what length bolt you need. For me I was able to weld the head of the bolt to the underside of the rebar so needed a shorter bolt. Measure centres of your step mount holes. Drill holes in the ply where the two piece meet using a 8.5mm bit if using m8 bolts. I calculated the measurement required to position the bolts evenly in the step and drilled the hole. This creates two precise 1/2 holes.

Determine stringer mounting hole centres, marking a line on the jig board. Place one of the freshly drilled pieces on that line. Depending on bolt size being used eg m8 bolt, move the piece 1/2 that diameter (eg 4mm) toward the closest end of the jig board. Repeat the other end. By offsetting the piece 1/2 the diameter of the bolt, we can now drill the bolt locating holes into the jig board using the piece of ply for perfect position.

You may need to create a recess in the jig upright to help position the bolt in an upright position.

Take two pieces of ply the width of the jig board and at least 40mm high. These are the stops for the long re bars that position the bolts correctly along them. Depending on the length of each step will depend on where the stops go. In my case 1000mm long. 30mm cover each end means the stops need to be about 940mm apart. Give yourself an extra couple of mm clearance to allow for slight cutting differences.

When you are ready to make a step, prepare the mold. I cleaned everything. Especially if the previous casting was a bit messy. It’s important to clean everything off the molds as bits tend to fall in and can ruin the finish. Using a scotch pad helps as does cleaning molds when the step is removed and still green.

Once cleaned I tried spraying the molds with RP7 and also silicone spray. I found both caused additional bubbles to form on the bottom of the cast step. I found without using any spray, mold release was still good because I was using form ply.

Clear your work space. I laid down plastic which made managing spills and splashes easy. Make sure all your tools are handy and clean. Organise cement and measure out required water.

Cut a re bar and to increase production speed and consistency, use one bar as a template. It made it alot quicker. I also decided to put in a cross member and used one as a guide as well..

Cut all the pieces needed.

I wired brushed all my pieces because of excess rust scale and gunk. Not really necessary but ocd kicked in.

To weld it all up, drop in 4 bolts and place two long re bars on the jig slots. Position two short bars against the upright of the rig. Tac in place. Position bolt against re bar and tac in place. Check everything looks good and weld it up. Bolts may need correcting afterward to re align. Tap lightly as required. To avoid damaging threads use a soft piece of wood and a hammer or attach a nut and only hit the nut.

Assemble the clean mold and place a piece of textured plastic at the bottom. Attach the ply locators (jig) to a welded reinforcing and secure with nuts. Tighten nut to adjust to correct depth. In my case the bolt was flush with the top of the nut. Should look like the first pic.

Mix the concrete. Adhere to mixing instructions. Just remember less water equals stronger concrete. Too dry and it won’t mix and you will have dry powder visible and will be hard to work with. Too wet and concrete will lose some of its mpa strength but will be easier to work with.

Calculate the required mix. Adjust for subsequent batches to reduce waste. My mold required 1 1/2 bag. I found this was a good amount for by tub. I tried mixing 3 bags at once and it was too much.

I added the desired amount of water to my round tub and then added the mix. I hand mixed with a small hand shovel to get it mostly mixed and then rolled the tub around to get a good consistency. In the second pic you can see how the cement was forming balls. This means it’s too dry. I added about a cup of water and the mixture was spot on as per pic three. A little water goes a long way. If you do make it too wet add a handful of cement powder at a time until it’s right.

Once the mix it done, pour or spoon into the mold. Once the mold is full, vibrate the mold and watch the bubbles come up. Above photo of two molds side by side shows one mold that was vibrated and the other not. You can over vibrate concrete so I vibrated each step for about a minute moving the tool every few seconds around the entire mold. A vibration table would be helpful to remove those stubborn bubbles at the bottom of the mold. You need to watch the reinforcing jig remain flat and in position and that the nuts don’t move.

Once the concrete is vibrated leave the step for at least an hour. There may be some bleed water rise in that time. Just leave it sit until the water disappears and the cement is still wet but getting firm. Even if the concrete is almost dry to the touch, it can be worked too a point a good finish can be obtained.

At this point, remove the jig pieces and center brace if your using one. Just be careful not to disturb the step too much. If left for too long the cement may stick as per the last pick. Don’t worry and just keep working the cement until it slurry’s somewhat and is workable. You can use your Maggie float before the bleed water starts and then again after if you want. If you use it for the final finish it will be a little rougher than using the steel float and may bring up the stones.

Leave step to fully harden eg overnight. De mold. I found unscrewing one corner made life a lot easier. Concrete takes up to 28days to fully cure. Leave them covered or in a shaded spot on their side for that time.

Happy building.