I suspect this is probably oversimplified, but I have heard that if you can frost a cake you can do cement work. What do yall think? ----- Original Message ----- From: Dale Leavens To: [email protected] Sent: Wednesday, May 23, 2007 5:59 PM Subject: Re: [BlindHandyMan] pouring cement stairs.
OK Dan, About troweling. I have three trowls I use, I will have to replace two next job if it is of any size, the third one is more commonly used for sticking mortar onto cement blocks or bricks. I will describe them. The mortar one is a flat steel plate roughly triangular in shape about 14 inches long from heel to toe shaped more or less like a linin iron. The handle comes off the top surface toward the rear sticking back. It is useful for working down along the form to get voids and bubbles out of the cement but it also works well as a small float or to pat the surface to help work up the cream. This tool isn't often used by cement workers, more commonly by brick and block layers but because I have one I often use it with cement as well. The more commonly used trowel is a rectangular piece of steel with a handle welded to one surface. These come in different sizes too. Mine is out in the shed just now but I guess it is about 12 inches by four inches. With the handle right over the center it is pretty good for tamping but the edge can be worked under things like the form for stair risers and it can be used as a float to. Finally there is the edging tool. This is about 6 inches long and about two and a half wide maybe three. It is rolled down on one edge and the ends are gently turned up. there is a handle across the non-working surface and it is used sliding lengthways to form a round over on the edge of concrete. Another common edging tool is a similar dimension but with a square bar running the length of the middle of the working surface. This is often used to form an edge on mating ends of sidewalk slabs while the round-over is more usually used to form the edges of the sidewalk slabs or the leading edges of stair treads. Another tool I and many other cement workers use is a length of board about thirty to thirty-six inches long and approaching four inches wide, a length of 2 by 4 will work fine but more usually one uses a bit of three quarter inch plywood, I am not sure why except maybe for the weight. You form a handle at right angles to one surface, usually people seem to form a "D" handle also of wood. This tool is usually the first one selected for tamping and screeding the surface flat. These seem to be home made tools, quite possibly there are commercial ones available but I have never seen one but I have seen many professional and amateur builders use them. Now in a big project the cement is first leveled with a bull float, a large flat think on a long arm handle. This is how they usually begin leveling something like a slab or basement floor, they may walk out on parts of it using plywood or something else to bear weight but usually they try not to do so. Once the slab begins to set up it is usual for commercial builders to get out on it with a power trowel which is something like a big floor polisher but with ceiling fan like paddles under it. Once the cement will hold a man without leaving significant prints this tool is worked over and over and over the floor along with gentle dampening which is how they get that wonderful smooth surface. It can be done by hand of course but it is murder on the back and knees and much slower. So, take your wooden trowel to firmly pat the concrete down and because of it's length to screed the surface reasonably level and flat by working it back and forth across the surface then take your rectangular trowel and similarly float it gently over the surface at first to get a feel for flat and level and as you work you will be polishing and bringing up the water with the light aggregate (the cream). this I always rather enjoy though it is murder on knees and back and hands. You may wish to repeat this step as the cement cures, it is remarkable how you can work up even more water when the surface feels really quite dry. That is often about the time to begin the edge treatment if you plan to do edge treatment, I recommend it as it really does add finish. Now for your sloping edges, if I understand you, this is an edge wall to the steps which begins ascending with a vertical face then slopes toward the middle for some distance before again ascending vertically. This would have to be formed up. It is nothing more than a design or decorative feature. One set of stairs I poured I formed up the sides thicker at top and bottom by applying a board top and bottom to the outside of the form which stepped it out about an inch for a height I think of four inches at the top and the bottom for decorative purposes mainly but to reinforce the side wall of the form. In your case it might also have been used to reduce the volume of cement required. I am not so sure bricks are a good filler material. Bricks are usually fired clay and might disintegrate embedded in concrete but cement block and rock and boulders and old scrap steel all work well. I suppose the old plywood box would ultimately rot and disappear I don't really know. Those steps were about three and a half feet wide and the top probably thirty inches front-to-back so allowing six inches each side and front and back the unsupported top would have been something like 30 inches wide and 18 or 20 inches deep and six inches thick. Should support a lot of weight, you might know a mechanical engineer who could give you more specific loading characteristics. I didn't put any rebar or pipe in it but I probably should have, you easily could, cut old bed frames or angle iron or just about anything to span the void and remember to set it in a little above the box. You could use rebar and form some skeleton inside tying it together with wire to keep it sinking in the wet concrete, the correct way of course is to weld it but I just remember that my father's generation didn't use rebar and they seemed to get away with it. You could even pull heavy galvanized steel wire through holes in the form weaving it back and forth and twisting it really tight to retain the forms while pouring. You then cut the wires off to remove the forms then cut them flush to the surface of the cement when you remove the forms. This steel wire will offer reinforcement to the cement. If you are really ambitious you might even parge a decorative surface over the walls to hide the wire ends. You can have loads of fun with forms of course, line the inside with that wavy plastic material often used for greenhousing and other roofing to add decoration. some even comes with a sort of grain pattern in it. Just remember that a slight angle or bevel makes removing the forms so much easier. Even a 90 degrees corner can grip every bit as tight as a dovetail. Remember too that the lime in cement will burn the skin off of you and it is carried in the water. I took the skin off of the front of my shins several years ago not hardly noticing that moisture was accumulating on the front of my work genes while I was troweling. Generally now I keep a rubber glove on my right hand and because I can't work well in a glove I keep a bucket of clear water around and an old towel so I have my left hand more or less free for touching but ready also for rinsing. Nevertheless I generally end up burning my finger prints off. I think I have addressed your questions, just let me know if I can clarify anything further. Dale Leavens, Cochrane Ontario Canada [EMAIL PROTECTED] Skype DaleLeavens Come and meet Aurora, Nakita and Nanook at our polar bear habitat. ----- Original Message ----- From: Dan Rossi To: [email protected] Sent: Wednesday, May 23, 2007 4:38 PM Subject: Re: [BlindHandyMan] pouring cement stairs. Thanks guys. I knew I could count on you. This is a future project, so I have some time to learn and do some experimenting. So Dale, I can build a hollow box and pour the steps over that? Will the wood eventually rot and the concrete will be strong enough to maintain it's structure? The side walls on my steps have this sloped section in the middle. The walls are about 14 inches wide. The walls have a flat spot at the top, a flat spot at the bottom, and this sloped section connecting the upper and lower plateau. Will the concrete be stiff enough to maintain that sloped surface, or would that have to be covered with the form? As far as the rubble. So I can just throw in anything rock-like into the wet concrete? Will cement blocks and old bricks be OK? As long as it stays well away from the edges. Now, here is the really nieve question. When you talk about troweling and really working the trowel, what does that mean exactly? Are you just moving the trowel back and forth smoothing over the surface? Are you tapping and patting the surface as well as moving back and forth across it? Are you plunging the edge of the trowel repeatedly into the surface to push down the aggregate and get the cream to float to the top? I think I might try making a few stepping stones before I try my hand at anything larger. -- Blue skies. Dan Rossi Carnegie Mellon University. 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