Rendering - how to get a flat finish?

Hello Nigel,

I have nearly plastered my kitchen with render, but I haven't done the finishing coat yet. I have learned a few things though. I have managed to get a reasonably flat surface in 1 coat, but a half inch of plaster/render is prone to crack, and the unevenness of the walls in my house means that there is massive variation of thickness, so I have found it easier to do 2 coats, the first is there to stick it on and to even out the large irregularities and the second to straighten. On large areas I have found setting up render screeds (lines of render every few feet to use as a guide) before the second coat very helpful. I have found all layers need rubbing with a float to consolidate the layer, even it up get rid of any cracks. There is a best time for this when the render has hardened up a bit so won't get dragged about, but it still soft enough for it to be redistributed. When applying the plaster I have found that moving the trowel over the surface horizontally as well as vertically helps get the render on a bit more evenly. On the second coat I have used straight pieces of wood to drag across the surface using the screeds as a guide to get it straighter before rubbing up with a float. Plastic floats are really cheap, and don't warp (have you been soaking your wooden float before using it, it needs to be well soaked so that the side that is rubbed on the plaster doesn't get more wet than the side with the handle which leads to the float warping to a convex shape) so I have been using plastic ones. If you want a finish that is slightly rough, you could use a sponge float rather than a sponge to finish, this does a surprisingly good job of redistributing the render even more, and also gives a rougher finish a bit more like stone. Sharp sand from a builders merchant has really big stones in so I have found plastering sand better. Lastly try a mix substituting for NHL with a 50:50 mix of NHL and hydrated lime. I have used this to point up below the dpc in a few parts of my house and it has gone hard, so will still set in damp places. It is much much easier to use as the hydrate makes it much more pliable and putty like. I honestly feel a bit cheated by companies selling NHL as I don't believe it is as appropriate for restoration as they suggest. I have rebuilt a few areas of my place with it and really wish I hadn't. I am convinced that 3.5 is too hard for building, pointing and especially plastering/rendering as it is so hard. I have found it as hard to remove from a few places as a cement mortar and nothing like as soft as the original mortar. It goes so hard that I wonder if it is just a lime cement mix, so I can only imagine NHL 5 is even more like cement!!!