diff --git a/src/LibHac/IO/PartitionFileSystemBuilder.cs b/src/LibHac/IO/PartitionFileSystemBuilder.cs
index 4e1bf45b..b4613940 100644
--- a/src/LibHac/IO/PartitionFileSystemBuilder.cs
+++ b/src/LibHac/IO/PartitionFileSystemBuilder.cs
@@ -14,6 +14,8 @@ namespace LibHac.IO
         private List<Entry> Entries { get; } = new List<Entry>();
         private long CurrentOffset { get; set; }
 
+        public PartitionFileSystemBuilder() { }
+
         /// <summary>
         /// Creates a new <see cref="PartitionFileSystemBuilder"/> and populates it with all
         /// the files in the root directory.
diff --git a/src/LibHac/Pfs0Builder.cs b/src/LibHac/Pfs0Builder.cs
deleted file mode 100644
index b8f9ceb7..00000000
--- a/src/LibHac/Pfs0Builder.cs
+++ /dev/null
@@ -1,75 +0,0 @@
-using System.Collections.Generic;
-using System.IO;
-
-namespace LibHac
-{
-    public class Pfs0Builder
-    {
-        private List<Entry> Entries { get; } = new List<Entry>();
-        private long DataLength { get; set; }
-
-        public void AddFile(string filename, Stream stream)
-        {
-            var entry = new Entry
-            {
-                Name = filename,
-                Stream = stream,
-                Length = stream.Length,
-                Offset = DataLength
-            };
-
-            DataLength += entry.Length;
-
-            Entries.Add(entry);
-        }
-
-        public void Build(Stream output, IProgressReport logger = null)
-        {
-            var strings = new MemoryStream();
-            var stringWriter = new BinaryWriter(strings);
-            var writer = new BinaryWriter(output);
-
-            foreach (Entry entry in Entries)
-            {
-                entry.StringOffset = (int)strings.Length;
-                stringWriter.WriteUTF8Z(entry.Name);
-            }
-
-            strings.Position = Util.GetNextMultiple(strings.Length, 0x10);
-            byte[] stringTable = strings.ToArray();
-
-            output.Position = 0;
-            writer.WriteUTF8("PFS0");
-            writer.Write(Entries.Count);
-            writer.Write(stringTable.Length);
-            writer.Write(0);
-
-            foreach (Entry entry in Entries)
-            {
-                writer.Write(entry.Offset);
-                writer.Write(entry.Length);
-                writer.Write(entry.StringOffset);
-                writer.Write(0);
-            }
-
-            writer.Write(stringTable);
-
-            foreach (Entry entry in Entries)
-            {
-                logger?.LogMessage(entry.Name);
-                entry.Stream.Position = 0;
-                entry.Stream.CopyStream(output, entry.Length, logger);
-            }
-            logger?.SetTotal(0);
-        }
-
-        private class Entry
-        {
-            public string Name;
-            public Stream Stream;
-            public long Length;
-            public long Offset;
-            public int StringOffset;
-        }
-    }
-}
diff --git a/src/hactoolnet/ProcessNsp.cs b/src/hactoolnet/ProcessPfs.cs
similarity index 88%
rename from src/hactoolnet/ProcessNsp.cs
rename to src/hactoolnet/ProcessPfs.cs
index 8a7267b5..4dedebdd 100644
--- a/src/hactoolnet/ProcessNsp.cs
+++ b/src/hactoolnet/ProcessPfs.cs
@@ -7,7 +7,7 @@ using static hactoolnet.Print;
 
 namespace hactoolnet
 {
-    internal static class ProcessNsp
+    internal static class ProcessPfs
     {
         public static void Process(Context ctx)
         {
@@ -65,11 +65,11 @@ namespace hactoolnet
                 return;
             }
 
-            var builder = new Pfs0Builder();
+            var builder = new PartitionFileSystemBuilder();
 
             foreach (Nca nca in title.Ncas)
             {
-                builder.AddFile(nca.Filename, nca.GetStorage().AsStream());
+                builder.AddFile(nca.Filename, nca.GetStorage().AsFile(OpenMode.Read));
             }
 
             var ticket = new Ticket
@@ -84,16 +84,16 @@ namespace hactoolnet
                 SectHeaderOffset = 0x2C0
             };
             byte[] ticketBytes = ticket.GetBytes();
-            builder.AddFile($"{ticket.RightsId.ToHexString()}.tik", new MemoryStream(ticketBytes));
+            builder.AddFile($"{ticket.RightsId.ToHexString()}.tik", new MemoryStream(ticketBytes).AsIFile(OpenMode.ReadWrite));
 
             Assembly thisAssembly = Assembly.GetExecutingAssembly();
             Stream cert = thisAssembly.GetManifestResourceStream("hactoolnet.CA00000003_XS00000020");
-            builder.AddFile($"{ticket.RightsId.ToHexString()}.cert", cert);
-
-
+            builder.AddFile($"{ticket.RightsId.ToHexString()}.cert", cert.AsIFile(OpenMode.Read));
+            
             using (var outStream = new FileStream(ctx.Options.NspOut, FileMode.Create, FileAccess.ReadWrite))
             {
-                builder.Build(outStream, ctx.Logger);
+                IStorage builtPfs = builder.Build(PartitionFileSystemType.Standard);
+                builtPfs.CopyToStream(outStream, builtPfs.Length, ctx.Logger);
             }
         }
     }
diff --git a/src/hactoolnet/ProcessSwitchFs.cs b/src/hactoolnet/ProcessSwitchFs.cs
index 8f4ec823..b82ad93a 100644
--- a/src/hactoolnet/ProcessSwitchFs.cs
+++ b/src/hactoolnet/ProcessSwitchFs.cs
@@ -136,7 +136,7 @@ namespace hactoolnet
 
             if (ctx.Options.NspOut != null)
             {
-                ProcessNsp.CreateNsp(ctx, switchFs);
+                ProcessPfs.CreateNsp(ctx, switchFs);
             }
 
             if (ctx.Options.SaveOutDir != null)
diff --git a/src/hactoolnet/Program.cs b/src/hactoolnet/Program.cs
index 5f7905cc..285231a1 100644
--- a/src/hactoolnet/Program.cs
+++ b/src/hactoolnet/Program.cs
@@ -59,7 +59,7 @@ namespace hactoolnet
                     break;
                 case FileType.Pfs0:
                 case FileType.Nsp:
-                    ProcessNsp.Process(ctx);
+                    ProcessPfs.Process(ctx);
                     break;
                 case FileType.PfsBuild:
                     ProcessFsBuild.ProcessPartitionFs(ctx);