diff --git a/app/__tests__/builderReducer.test.ts b/app/__tests__/builderReducer.test.ts
index 0a2b53ab..9ef5cab6 100644
--- a/app/__tests__/builderReducer.test.ts
+++ b/app/__tests__/builderReducer.test.ts
@@ -110,6 +110,18 @@ test('short word warning', () => {
     ]
   `);
 });
+test('isolated cell warning', () => {
+  const state = getState(
+    ['a', 'b', 'c', 'd', 'e', '.', 'f', '.', 'g'],
+    {}
+  );
+
+  expect(builderReducer(state, publish).publishWarnings).toMatchInlineSnapshot(`
+    [
+      "Some cells are not part of any word",
+    ]
+  `);
+});
 
 test('basic enum warnings', () => {
   const state = getState(['a', 'b', 'c', 'g', '', '', 'd', 'e', 'f'], {
diff --git a/app/reducers/builderReducer.ts b/app/reducers/builderReducer.ts
index 4f23565e..059002b0 100644
--- a/app/reducers/builderReducer.ts
+++ b/app/reducers/builderReducer.ts
@@ -1037,6 +1037,9 @@ function _builderReducer(
           Array.from(stats.shortWords).sort().join(', ') +
           ')'
       );
+      if (stats.isolatedCells.size > 0) {
+  warnings.push('Some cells are not part of any word');
+}
     }
     if (stats.hasUnches) {
       warnings.push('UNCHES'); // A bit of a hack but PublishWarningsList handles rendering this one
diff --git a/app/reducers/builderUtils.ts b/app/reducers/builderUtils.ts
index 8401139d..1f3d6e6d 100644
--- a/app/reducers/builderUtils.ts
+++ b/app/reducers/builderUtils.ts
@@ -81,13 +81,25 @@ export function getWarningStats(state: BuilderState) {
   const { clues, grid } = state;
   const { entries, sortedEntries } = grid;
 
-  const shortWords = new Set<string>();
+ const shortWords = new Set<string>();
 
-  for (const [i, entry] of entries.entries()) {
-    if (entry.completedWord && entry.completedWord.length <= 2) {
-      shortWords.add(entryWord(grid, i));
-    }
+for (const [i, entry] of entries.entries()) {
+  if (entry.completedWord && entry.completedWord.length <= 2) {
+    shortWords.add(entryWord(grid, i));
   }
+}
+
+const isolatedCells = new Set<number>();
+
+for (const [i, cellEntries] of grid.entriesByCell.entries()) {
+  if (
+    grid.cells[i] !== '.' &&
+    cellEntries[0].entryIndex === null &&
+    cellEntries[1].entryIndex === null
+  ) {
+    isolatedCells.add(i);
+  }
+}
 
   const unmatchedRefs = new Set<string>();
   const missingEnums = new Set<string>();
@@ -128,13 +140,14 @@ export function getWarningStats(state: BuilderState) {
   });
   const enumsExpected = missingEnums.size < numValidClues / 2;
 
-  return {
-    shortWords,
-    hasUnches: hasUnches(grid) && !state.userTags.includes('cryptic'),
-    unmatchedRefs,
-    missingEnums: enumsExpected ? missingEnums : null,
-    wrongEnums: enumsExpected ? wrongEnums : null,
-  };
+ return {
+  shortWords,
+  isolatedCells,
+  hasUnches: hasUnches(grid) && !state.userTags.includes('cryptic'),
+  unmatchedRefs,
+  missingEnums: enumsExpected ? missingEnums : null,
+  wrongEnums: enumsExpected ? wrongEnums : null,
+};
 }
 
 export function hasSelection(state: GridInterfaceState): boolean {