# How can I add extra space before \cline in a \multicolumn matrix cell?

I'm trying to make this matrix looks nicer. Currently the horizontal line coincides with the $A^\top$. How can I make it so $A^\top$ doesn't intersect with the horizontal line? This is what I have:

\documentclass{article}
\usepackage{amsmath}

\begin{document}
Original matrix:

$\left[\begin{array}{cccc} \multicolumn{1}{c|}{A^\top}\\ \cline{1-2} ~&\multicolumn{1}{|c|}{A^\top}\\ \cline{2-2} ~&~&\ddots\\ \cline{4-4} ~&~&~&\multicolumn{1}{|c}{A^\top} \\ \end{array} \right]$

Matrix with .25cm space after each row

$\left[\begin{array}{cccc} \multicolumn{1}{c|}{A^\top}\\[.25cm] \cline{1-2} ~&\multicolumn{1}{|c|}{A^\top}\\[.25cm] \cline{2-2} ~&~&\ddots\\[.25cm] \cline{4-4} ~&~&~&\multicolumn{1}{|c}{A^\top} \\[.25cm] \end{array} \right]$
\end{document}


I wrapped the A^\top in an \addstackgap (stackengine package). The default vertical gap added is 3pt, which can be redefined (\setstackgap{S}{5pt}) or else overridden with an optional argument (\addstackgap[5pt]{...}).

\documentclass{article}
\usepackage{amsmath,stackengine}
\stackMath
\begin{document}
Original matrix:

$\left[\begin{array}{cccc} \multicolumn{1}{c|}{A^\top}\\ \cline{1-2} ~&\multicolumn{1}{|c|}{\addstackgap{A^\top}}\\ \cline{2-2} ~&~&\ddots\\ \cline{4-4} ~&~&~&\multicolumn{1}{|c}{\addstackgap{A^\top}} \\ \end{array} \right]$

\end{document}


Another possibility with bigstrut cellspace and booktabs:

\documentclass{article}
\usepackage{amsmath}
\usepackage{booktabs}
\usepackage{bigstrut}
\usepackage{cellspace} %

\begin{document}

Original matrix:

$\left[\begin{array}{cccc} \multicolumn{1}{c|}{A^\top}\\ \cline{1-2} ~&\multicolumn{1}{|c|}{A^\top}\\ \cline{2-2} ~&~&\ddots\\ \cline{4-4} ~&~&~&\multicolumn{1}{|c}{A^\top} \\ \end{array} \right]$
\vskip1cm
$\setlength{\aboverulesep}{0pt}\setlength{\belowrulesep}{0pt} \setlength{\cmidrulewidth}{0.4pt}\bigstrutjot=4pt \begin{bmatrix} \multicolumn{1}{c|}{A^{\top}\bigstrut[t]}\\ \cmidrule(l{0.35em}){1-2} &\multicolumn{1}{!{\kern-0.4pt\vrule}c|}{A^{\top}\bigstrut[t]}\\[-0.4pt] \cmidrule{2-2} & & \ddots\\ \cmidrule(r{0.35em}){4-4} & & &\multicolumn{1}{|c}{A^{\top}\bigstrut} \end{bmatrix}$

\end{document}