diff --git a/src/pvxs/data.h b/src/pvxs/data.h
index e85a0de..f4658fb 100644
--- a/src/pvxs/data.h
+++ b/src/pvxs/data.h
@@ -193,6 +193,9 @@ struct Member {
     Member(TypeCode code, const std::string& name, std::initializer_list<Member> children)
         :Member(code, name , std::string(), children)
     {}
+
+    PVXS_API
+    void addChild(const Member& mem);
 };
 
 /** Helper functions for building TypeDef.
diff --git a/src/type.cpp b/src/type.cpp
index eec08a4..5a07a86 100644
--- a/src/type.cpp
+++ b/src/type.cpp
@@ -132,6 +132,12 @@ Member::Member(TypeCode code, const std::string& name, const std::string& id, st
     }
 }
 
+void Member::addChild(const Member& mem)
+{
+    node_validate(this, mem.id, mem.code);
+    children.push_back(mem);
+}
+
 static
 void build_tree(std::vector<FieldDesc>& desc, const Member& node)
 {