The height of any row in a Tablix can be adjusted by changing the height of a single cell in the row. All cells in that row will then take on the height of the last changed cell, i.e. if you change the height of a cell in the first column to 0.5” and then change a cell in the second column of the same row to 0.125” the entire row height will change to 0.125”. To change the row Height property in Report Builder or BIDS: Select a single cell, scroll down in the Properties window to the section ‘Position’, expand the subsection ‘Size’ and then edit ‘Height’.
A special note on Tablix row heights when the report is rendered; by default a row will adjust to the height of its content. Typically content is text and if the row height cannot accommodate a second line of text for long strings then the row will grow taller than the set row Height to accommodate the text. If the effect is not desirable then you can change the CanGrow property to False. To change the CanGrow property for a row: Select the row handle at the left to select all cells in that row, scroll down in the Properties window to the section ‘Genera’l and change’ CanGrow’ to False. This is most useful when you have a blank row in a Tablix that is being used for line spacing; otherwise the row will automatically take on the height of the font size even though there is no text, e.g. an empty row with font size 18 will not remain the height of 0.0625” when the report is rendered.
The same concept for rows holds true for columns when a cell’s Width is adjusted, except they cannot grow or shrink like the height can when the report is rendered. Also note that when cells are merged with the adjacent cells that typically the column that makes up the far right of the section will increase to the right when the merged cell’s width is increased. Therefore it is typically best to split the cells when adjusting column widths to avoid this and avoid columns that cannot be decreased in width.