<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> Screed has three meanings in building construction: 1) a flat board (screed board, floating screed) or a purpose - made aluminium tool used to smooth and true materials like concrete, stucco and plaster after it has been placed on a surface or to assist in flattening; 2) a strip of plaster or wood applied to a surface to act as a guide for a screed tool (screed rail, screed strip, screed batten); 3) the material itself which has been flattened with a screed (screed coat). In the UK, screed has also come to describe a thin, top layer of material (traditionally sand and cement), poured in site on top of the structural concrete or insulation, on top of which other finishing materials can be applied, or it can be left bare to achieve a raw effect . </P> <P> In the US, screeding is the process a person called a concrete finisher performs by cutting off excess wet concrete to bring the top surface of a slab to the proper grade and smoothness . A power concrete screed has a gasoline motor attached which helps smooth and vibrate concrete as it is flattened . After the concrete is flattened it is smoothed with a concrete float or power trowel . A concrete floor is sometimes called a solid ground floor . </P>

What is the top layer of concrete called