Sometimes, those first sketches have a dynamism to them that falls apart when you try to draw them formally. So how do you take that initial energy and refine it to a coherent plan? First, pick one of the sketches that you feel good about the spatial relationships and overlay a sheet of tracing paper on it. Try not to refine any of the shapes, but just trace the outlines of the exterior walls, any large dividing partitions, and any door and window openings (don’t worry about furniture or other interior elements). You should just see the outline of the big bones of the space.
Look at this outline and ask yourself if walls are logically aligned, if there are long distances between structural elements. It is easy to draw long expanses of unsupported space when you’re working in a very loose, gestural way, but it is often better to add some intermediate support (such as a column or a smaller wall) to make the space more realistic and liveable. Don’t think of structure as something to fight against. Instead, it’s a way to help establish proportions and organize your space in a way that gestural sketching cannot.
Then, look at how the vertical elements (door and window openings) relate to the horizontal ones (walls and partitions). Don’t place openings in random locations; try to find locations that are more intentional, perhaps on an axis with something else. If you find that navigating through your plan is somewhat confusing, try tracing the path someone would walk through it with a continuous line. If the line has sharp angles or pinches, you may want to reconsider how you’ve designed your space. It’s much easier to refine the circulation of your plan now than later, and it will make your drawing seem more intentional and less accidental.
Try this simple exercise for a few minutes a day: take one of your loose sketches and trace it with a ruler to clean it up, and then dimension it approximately (you can use standard room dimensions as a rough guide). Even if your dimensions aren’t accurate, it will help you learn to think about the proportions of a space. If you do this daily, you will eventually find that you need to make fewer changes to your initial sketch to get to something viable.
If you need help, look at an existing building plan for inspiration rather than one of your other sketches. You’ll notice that the arrangement of thicknesses, alignments and repetitions create a coherence. Try to achieve this in your plan while still retaining the essence of your initial idea. You don’t need to lose the spontaneity of your sketch, but you do need to understand how it will be constructed in order to make it real.