:memo: add more specifics about required .net
diff --git a/BUILDING.md b/BUILDING.md
index 7d5e050..0a0cbd1 100644
--- a/BUILDING.md
+++ b/BUILDING.md
@@ -11,6 +11,9 @@
 - build locally. Suggested environment:
     - Pre-requisites:
         - Visual Studio 2019 Build Tools
+            - include desktop targets at least
+            - include dotnet core targets or download and install
+                the latest dotnet sdk (you will need at least v2.1)
         - Ensure you have .NET Framework 3.5 SP1 installed
             - on Win10+, this can only be installed via Add/Remove Windows Components
             - on other platforms, see https://dotnet.microsoft.com/download/dotnet-framework/net35-sp1