  Let $\mathbb F$ be a real closed field. We define the notion of a maximal
framing for a representation of the fundamental group of a surface with values
in ${\rm Sp}(2n,\mathbb F)$. We show that ultralimits of maximal
representations in ${\rm Sp}(2n,\mathbb R)$ admit such a framing, and that all
maximal framed representations satisfy a suitable generalisation of the
classical Collar Lemma. In particular this establishes a Collar Lemma for all
maximal representations into ${\rm Sp}(2n,\mathbb R)$. We then describe a
procedure to get from representations in ${\rm Sp}(2n,\mathbb F)$ interesting
actions on affine buildings, and, in the case of representations admitting a
maximal framing, we describe the structure of the elements of the group acting
with zero translation length.
