zps215 has a better answer, even if it does not use ngMaterial, the effect you are looking for is best resolved using plain CSS. However, the best solution would be to use padding for the parent container, not the field.
.container { padding: 20px; }
However, if you really need to solve this problem with ngMaterial, you can put the markup in another div element and add a layout field to it.
<div layout-margin> <div layout="row"> <div flex>Parent layout and this element have margins.</div> </div> </div>
This would have the same desired effect, although it could be confusing to anyone who adds children to this div, as they also receive margins.
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