Index: Ringtoets/Common/src/Ringtoets.Common.Data/IllustrationPoints/TopLevelFaultTreeIllustrationPoint.cs
===================================================================
diff -u -r72cdd802a67613c6e93bb92ae0b1478c5c943b0a -r723e8357991d59d7784212cb433bb4571e0cdefb
--- Ringtoets/Common/src/Ringtoets.Common.Data/IllustrationPoints/TopLevelFaultTreeIllustrationPoint.cs	(.../TopLevelFaultTreeIllustrationPoint.cs)	(revision 72cdd802a67613c6e93bb92ae0b1478c5c943b0a)
+++ Ringtoets/Common/src/Ringtoets.Common.Data/IllustrationPoints/TopLevelFaultTreeIllustrationPoint.cs	(.../TopLevelFaultTreeIllustrationPoint.cs)	(revision 723e8357991d59d7784212cb433bb4571e0cdefb)
@@ -27,7 +27,7 @@
     /// Represents the top level combination of wind direction, closing situation
     /// and the fault tree.
     /// </summary>
-    public class TopLevelFaultTreeIllustrationPoint
+    public class TopLevelFaultTreeIllustrationPoint : TopLevelIllustrationPointBase
     {
         /// <summary>
         /// Creates an instance of <see cref="TopLevelFaultTreeIllustrationPoint"/>.
@@ -40,6 +40,7 @@
         public TopLevelFaultTreeIllustrationPoint(WindDirection windDirection,
                                                   string closingSituation,
                                                   FaultTreeIllustrationPointNode faultTreeNodeRoot)
+            : base(windDirection, closingSituation)
         {
             if (windDirection == null)
             {
@@ -54,22 +55,10 @@
                 throw new ArgumentNullException(nameof(faultTreeNodeRoot));
             }
 
-            WindDirection = windDirection;
-            ClosingSituation = closingSituation;
             FaultTreeNodeRoot = faultTreeNodeRoot;
         }
 
         /// <summary>
-        /// Gets the wind direction.
-        /// </summary>
-        public WindDirection WindDirection { get; }
-
-        /// <summary>
-        /// Gets the closing situation.
-        /// </summary>
-        public string ClosingSituation { get; }
-
-        /// <summary>
         /// Gets the root of the illustration points of the fault tree. 
         /// </summary>
         public FaultTreeIllustrationPointNode FaultTreeNodeRoot { get; }
Index: Ringtoets/Common/src/Ringtoets.Common.Data/IllustrationPoints/TopLevelIllustrationPointBase.cs
===================================================================
diff -u
--- Ringtoets/Common/src/Ringtoets.Common.Data/IllustrationPoints/TopLevelIllustrationPointBase.cs	(revision 0)
+++ Ringtoets/Common/src/Ringtoets.Common.Data/IllustrationPoints/TopLevelIllustrationPointBase.cs	(revision 723e8357991d59d7784212cb433bb4571e0cdefb)
@@ -0,0 +1,64 @@
+// Copyright (C) Stichting Deltares 2017. All rights reserved.
+//
+// This file is part of Ringtoets.
+//
+// Ringtoets is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+//
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using System;
+
+namespace Ringtoets.Common.Data.IllustrationPoints
+{
+    /// <summary>
+    /// A base class for combinations of wind direction, closing situations 
+    /// and illustration points.
+    /// </summary>
+    public abstract class TopLevelIllustrationPointBase
+    {
+        /// <summary>
+        /// Creates a <see cref="TopLevelIllustrationPointBase"/>.
+        /// </summary>
+        /// <param name="windDirection">The wind direction.</param>
+        /// <param name="closingSituation">The closing situation.</param>
+        /// <exception cref="ArgumentNullException">Thrown when any of the parameters
+        /// is <c>null</c>.</exception>
+        protected TopLevelIllustrationPointBase(WindDirection windDirection, string closingSituation)
+        {
+            if (windDirection == null)
+            {
+                throw new ArgumentNullException(nameof(windDirection));
+            }
+            if (closingSituation == null)
+            {
+                throw new ArgumentNullException(nameof(closingSituation));
+            }
+
+            WindDirection = windDirection;
+            ClosingSituation = closingSituation;
+        }
+
+        /// <summary>
+        /// Gets the wind direction.
+        /// </summary>
+        public WindDirection WindDirection { get; }
+
+        /// <summary>
+        /// Gets the closing situation.
+        /// </summary>
+        public string ClosingSituation { get; }
+    }
+}
\ No newline at end of file
Index: Ringtoets/Common/src/Ringtoets.Common.Data/IllustrationPoints/TopLevelSubMechanismIllustrationPoint.cs
===================================================================
diff -u -r72cdd802a67613c6e93bb92ae0b1478c5c943b0a -r723e8357991d59d7784212cb433bb4571e0cdefb
--- Ringtoets/Common/src/Ringtoets.Common.Data/IllustrationPoints/TopLevelSubMechanismIllustrationPoint.cs	(.../TopLevelSubMechanismIllustrationPoint.cs)	(revision 72cdd802a67613c6e93bb92ae0b1478c5c943b0a)
+++ Ringtoets/Common/src/Ringtoets.Common.Data/IllustrationPoints/TopLevelSubMechanismIllustrationPoint.cs	(.../TopLevelSubMechanismIllustrationPoint.cs)	(revision 723e8357991d59d7784212cb433bb4571e0cdefb)
@@ -27,7 +27,7 @@
     /// Represents the top level combination of wind direction, closing situation and 
     /// a submechanism illustration point.
     /// </summary>
-    public class TopLevelSubMechanismIllustrationPoint
+    public class TopLevelSubMechanismIllustrationPoint : TopLevelIllustrationPointBase
     {
         /// <summary>
         /// Creates a new instance of <see cref="TopLevelSubMechanismIllustrationPoint"/>.
@@ -38,7 +38,8 @@
         /// <exception cref="ArgumentNullException">Thrown when any input parameter is <c>null</c>.</exception>
         public TopLevelSubMechanismIllustrationPoint(WindDirection windDirection,
                                                      string closingSituation,
-                                                     SubMechanismIllustrationPoint subMechanismIllustrationPoint)
+                                                     SubMechanismIllustrationPoint subMechanismIllustrationPoint) 
+            : base(windDirection, closingSituation)
         {
             if (windDirection == null)
             {
@@ -53,22 +54,10 @@
                 throw new ArgumentNullException(nameof(subMechanismIllustrationPoint));
             }
 
-            WindDirection = windDirection;
-            ClosingSituation = closingSituation;
             SubMechanismIllustrationPoint = subMechanismIllustrationPoint;
         }
 
         /// <summary>
-        /// Gets the closing situation.
-        /// </summary>
-        public string ClosingSituation { get; }
-
-        /// <summary>
-        /// Gets the wind direction.
-        /// </summary>
-        public WindDirection WindDirection { get; }
-
-        /// <summary>
         /// Gets the submechanism illustration point.
         /// </summary>
         public SubMechanismIllustrationPoint SubMechanismIllustrationPoint { get; }
Index: Ringtoets/Common/src/Ringtoets.Common.Data/Ringtoets.Common.Data.csproj
===================================================================
diff -u -r72cdd802a67613c6e93bb92ae0b1478c5c943b0a -r723e8357991d59d7784212cb433bb4571e0cdefb
--- Ringtoets/Common/src/Ringtoets.Common.Data/Ringtoets.Common.Data.csproj	(.../Ringtoets.Common.Data.csproj)	(revision 72cdd802a67613c6e93bb92ae0b1478c5c943b0a)
+++ Ringtoets/Common/src/Ringtoets.Common.Data/Ringtoets.Common.Data.csproj	(.../Ringtoets.Common.Data.csproj)	(revision 723e8357991d59d7784212cb433bb4571e0cdefb)
@@ -76,6 +76,7 @@
     <Compile Include="IllustrationPoints\SubMechanismIllustrationPoint.cs" />
     <Compile Include="IllustrationPoints\IllustrationPointResult.cs" />
     <Compile Include="IllustrationPoints\TopLevelFaultTreeIllustrationPoint.cs" />
+    <Compile Include="IllustrationPoints\TopLevelIllustrationPointBase.cs" />
     <Compile Include="IllustrationPoints\WindDirection.cs" />
     <Compile Include="IllustrationPoints\SubMechanismIllustrationPointStochast.cs" />
     <Compile Include="IllustrationPoints\Stochast.cs" />
Index: Ringtoets/Common/test/Ringtoets.Common.Data.Test/IllustrationPoints/TopLevelFaultTreeIllustrationPointTest.cs
===================================================================
diff -u -r72cdd802a67613c6e93bb92ae0b1478c5c943b0a -r723e8357991d59d7784212cb433bb4571e0cdefb
--- Ringtoets/Common/test/Ringtoets.Common.Data.Test/IllustrationPoints/TopLevelFaultTreeIllustrationPointTest.cs	(.../TopLevelFaultTreeIllustrationPointTest.cs)	(revision 72cdd802a67613c6e93bb92ae0b1478c5c943b0a)
+++ Ringtoets/Common/test/Ringtoets.Common.Data.Test/IllustrationPoints/TopLevelFaultTreeIllustrationPointTest.cs	(.../TopLevelFaultTreeIllustrationPointTest.cs)	(revision 723e8357991d59d7784212cb433bb4571e0cdefb)
@@ -87,6 +87,8 @@
             var illustrationPoint = new TopLevelFaultTreeIllustrationPoint(windDirection, closingSituation, faultTreeNode);
 
             // Assert
+            Assert.IsInstanceOf<TopLevelIllustrationPointBase>(illustrationPoint);
+
             Assert.AreSame(windDirection, illustrationPoint.WindDirection);
             Assert.AreEqual(closingSituation, illustrationPoint.ClosingSituation);
             Assert.AreSame(faultTreeNode, illustrationPoint.FaultTreeNodeRoot);
Index: Ringtoets/Common/test/Ringtoets.Common.Data.Test/IllustrationPoints/TopLevelIllustrationPointBaseTest.cs
===================================================================
diff -u
--- Ringtoets/Common/test/Ringtoets.Common.Data.Test/IllustrationPoints/TopLevelIllustrationPointBaseTest.cs	(revision 0)
+++ Ringtoets/Common/test/Ringtoets.Common.Data.Test/IllustrationPoints/TopLevelIllustrationPointBaseTest.cs	(revision 723e8357991d59d7784212cb433bb4571e0cdefb)
@@ -0,0 +1,86 @@
+// Copyright (C) Stichting Deltares 2017. All rights reserved.
+//
+// This file is part of Ringtoets.
+//
+// Ringtoets is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+//
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using System;
+using NUnit.Framework;
+using Ringtoets.Common.Data.IllustrationPoints;
+
+namespace Ringtoets.Common.Data.Test.IllustrationPoints
+{
+    [TestFixture]
+    public class TopLevelIllustrationPointBaseTest
+    {
+        [Test]
+        public void Constructor_WindDirectionNull_ThrowsArgumentNullException()
+        {
+            // Call
+            TestDelegate call = () => new TestTopLevelIllustrationPointBase(null, "closing situation");
+
+            // Assert
+            var exception = Assert.Throws<ArgumentNullException>(call);
+            Assert.AreEqual("windDirection", exception.ParamName);
+        }
+
+        [Test]
+        public void Constructor_ClosingSituationNull_ThrowsArgumentNullException()
+        {
+            // Setup
+            var random = new Random(21);
+
+            const string windDirectionName = "Name of the wind";
+            double windDirectionAngle = random.NextDouble();
+            var windDirection = new WindDirection(windDirectionName, windDirectionAngle);
+
+            // Call
+            TestDelegate call = () => new TestTopLevelIllustrationPointBase(windDirection, null);
+
+            // Assert
+            var exception = Assert.Throws<ArgumentNullException>(call);
+            Assert.AreEqual("closingSituation", exception.ParamName);
+        }
+
+        [Test]
+        public void Constructor_ValidArguments_ReturnExpectedValues()
+        {
+            // Setup
+            var random = new Random(21);
+
+            const string windDirectionName = "Name of the wind";
+            double windDirectionAngle = random.NextDouble();
+            var windDirection = new WindDirection(windDirectionName, windDirectionAngle);
+
+            const string closingSituation = "closing situation";
+
+            // Call
+            var topLevelIllustrationPoint = new TestTopLevelIllustrationPointBase(windDirection, closingSituation);
+
+            // Assert
+            Assert.AreSame(windDirection, topLevelIllustrationPoint.WindDirection);
+            Assert.AreEqual(closingSituation, topLevelIllustrationPoint.ClosingSituation);
+        }
+
+        private class TestTopLevelIllustrationPointBase : TopLevelIllustrationPointBase
+        {
+            public TestTopLevelIllustrationPointBase(WindDirection windDirection, string closingSituation)
+                : base(windDirection, closingSituation) {}
+        }
+    }
+}
\ No newline at end of file
Index: Ringtoets/Common/test/Ringtoets.Common.Data.Test/IllustrationPoints/TopLevelSubMechanismIllustrationPointTest.cs
===================================================================
diff -u -rb7988d7a5616c8c305dac4419a15d5eda07e88bc -r723e8357991d59d7784212cb433bb4571e0cdefb
--- Ringtoets/Common/test/Ringtoets.Common.Data.Test/IllustrationPoints/TopLevelSubMechanismIllustrationPointTest.cs	(.../TopLevelSubMechanismIllustrationPointTest.cs)	(revision b7988d7a5616c8c305dac4419a15d5eda07e88bc)
+++ Ringtoets/Common/test/Ringtoets.Common.Data.Test/IllustrationPoints/TopLevelSubMechanismIllustrationPointTest.cs	(.../TopLevelSubMechanismIllustrationPointTest.cs)	(revision 723e8357991d59d7784212cb433bb4571e0cdefb)
@@ -88,6 +88,8 @@
                 new TopLevelSubMechanismIllustrationPoint(windDirection, closingScenario, submechanismIllustrationPoint);
 
             // Assert
+            Assert.IsInstanceOf<TopLevelIllustrationPointBase>(windDirectionClosingScenarioIllustrationPoint);
+
             Assert.AreEqual(closingScenario, windDirectionClosingScenarioIllustrationPoint.ClosingSituation);
             Assert.AreSame(windDirection, windDirectionClosingScenarioIllustrationPoint.WindDirection);
             Assert.AreSame(submechanismIllustrationPoint, windDirectionClosingScenarioIllustrationPoint.SubMechanismIllustrationPoint);
Index: Ringtoets/Common/test/Ringtoets.Common.Data.Test/Ringtoets.Common.Data.Test.csproj
===================================================================
diff -u -r72cdd802a67613c6e93bb92ae0b1478c5c943b0a -r723e8357991d59d7784212cb433bb4571e0cdefb
--- Ringtoets/Common/test/Ringtoets.Common.Data.Test/Ringtoets.Common.Data.Test.csproj	(.../Ringtoets.Common.Data.Test.csproj)	(revision 72cdd802a67613c6e93bb92ae0b1478c5c943b0a)
+++ Ringtoets/Common/test/Ringtoets.Common.Data.Test/Ringtoets.Common.Data.Test.csproj	(.../Ringtoets.Common.Data.Test.csproj)	(revision 723e8357991d59d7784212cb433bb4571e0cdefb)
@@ -89,6 +89,7 @@
     <Compile Include="IllustrationPoints\SubMechanismIllustrationPointStochastTest.cs" />
     <Compile Include="IllustrationPoints\StochastTest.cs" />
     <Compile Include="IllustrationPoints\TopLevelFaultTreeIllustrationPointTest.cs" />
+    <Compile Include="IllustrationPoints\TopLevelIllustrationPointBaseTest.cs" />
     <Compile Include="IllustrationPoints\TopLevelSubMechanismIllustrationPointTest.cs" />
     <Compile Include="IllustrationPoints\WindDirectionTest.cs" />
     <Compile Include="Hydraulics\WaveHeightCalculationTest.cs" />