According to examples, a system may include a recoater and a controller. The controller may identify a structure of a surface of a layer of build material formed on a build platform and may determine whether the identified structure of the surface includes a portion that has a property that is outside of a predefined property level. Based on a determination that the portion has a property that is outside of the predefined property level, an adjustment to be applied to an operation of the recoater to achieve an intended structure of the layer and/or an intended structure of a subsequent layer may be determined and the determined adjustment on the operation of the recoater may be applied.