A formwork is used to mold a masonry work. The example taken here consists in manufacturing a formwork for the molding of a window sill. Choose a good quality wood, at least 27 mm thick. Indeed, even for a small structure, the weight of the concrete contained in a formwork is important and the wood used must be able to withstand it without breaking. Also be aware that there are special particle board or plywood.
- Folding Meter
- Formwork wood
- Prepare the pieces of wood
- Assemble the formwork
Prepare the pieces of wood
1. The mold is made of a facade, two cheeks delimiting the sides of the window sill and a bottom. After drawing the elements to the required dimensions (depending on the width of the window), hold the piece of wood on the bench and cut it out. Use a power saw (jigsaw or circular saw): it makes the task easier and guarantees the necessary precision.
2. After cutting, plan the pieces of wood. The regularity and flatness of the elements of the formwork must be perfect, the quality of the work depends on it. The handling of the plane (here a metal plane) is relatively simple: push the tool with one hand and guide it with the other, without pressing it. The planks must be well erected: no day must remain between them, once assembled, to contain the concrete, quite liquid at the time of pouring.
Assemble the formwork
1. Secure the bottom of the formwork and place the front so that its edge is flush with the outside of the back. Hold the pieces together and assemble them by pushing in a few points. Be careful, do not push them at an angle: if they protrude, they risk being sealed in the concrete, thus damaging the structure, or hindering the stripping. The safest method is to postpone the thickness of the bottom on the facade: this mark indicates the area in the middle of which you have to push the tips.
2. With the flanges of the formwork cut out, cut them to the dimensions of the quarter-round to be arranged later. Spread the cheeks according to the width to be given to the support, this measurement being a function of the window itself. Place each of the cheeks vertically on the bottom: the verticality, essential, conditions that of the sides of the window sill. Solidarize the cheeks to the formwork by nailing, pushing the points from the outside facing of the facade.
3. Cut a quarter-round section corresponding to the gap of the cheeks, increased by the thickness of these (ie 40 mm for the wood used here). This quarter-round will form a slope under the support, over the entire length, which will act as a gutter: this stops the rainwater that would otherwise run on the wall. Place the quarter circle around the center of the formwork, and fix it by nailing. Preferably use headless tips, which you will then chase.
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