diff --git a/.changeset/thirty-readers-draw.md b/.changeset/thirty-readers-draw.md
new file mode 100644
index 0000000..6073acb
--- /dev/null
+++ b/.changeset/thirty-readers-draw.md
@@ -0,0 +1,5 @@
+---
+'gov4git-desktop-app': patch
+---
+
+Pin header
diff --git a/src/renderer/src/App/App.css b/src/renderer/src/App/App.css
index 8b6957a..1e99237 100644
--- a/src/renderer/src/App/App.css
+++ b/src/renderer/src/App/App.css
@@ -10,22 +10,22 @@ html {
 }
 
 html {
-  height: 100%;
+  height: 100vh;
 }
 body {
-  min-height: 100%;
+  height: 100vh;
 }
 
 #root {
-  min-height: 100%;
+  height: 100vh;
   /* min-height: 100%; */
   /* overflow-x: hidden; */
   background-color: #f3f3f3;
 }
 
 #fluent-provider {
-  min-height: 100%;
-  /* overflow-x: hidden; */
+  height: 100vh;
+  overflow-y: hidden;
   background-color: transparent;
 }
 
diff --git a/src/renderer/src/components/SiteNav.styles.ts b/src/renderer/src/components/SiteNav.styles.ts
index 25eb2b8..6f429b4 100644
--- a/src/renderer/src/components/SiteNav.styles.ts
+++ b/src/renderer/src/components/SiteNav.styles.ts
@@ -12,9 +12,7 @@ export const useSiteNavStyles = makeStyles({
     position: 'sticky',
     top: '0',
     width: '75px',
-    maxHeight: '100vh',
-    // height of the header is 60px
-    minHeight: 'calc(100vh - 60px)',
+    height: 'calc(100vh - 60px)',
     zIndex: '100',
     flexBasis: 'auto',
     flexGrow: '0',
@@ -27,7 +25,6 @@ export const useSiteNavStyles = makeStyles({
   },
   absoluteContainer: {
     backgroundColor: gov4GitTokens.colorNeutralBackground1,
-    // backgroundColor: gov4GitTokens.g4gColorPrimaryGreen1,
     position: 'absolute',
     top: '0',
     minHeight: '100%',
diff --git a/src/renderer/src/pages/Layout.styles.ts b/src/renderer/src/pages/Layout.styles.ts
index c6632ac..69c5829 100644
--- a/src/renderer/src/pages/Layout.styles.ts
+++ b/src/renderer/src/pages/Layout.styles.ts
@@ -6,8 +6,9 @@ export const useLayoutStyles = makeStyles({
   layout: {
     display: 'flex',
     flexDirection: 'column',
-    minHeight: '100%',
+    height: '100%',
     width: '100%',
+    overflowY: 'hidden',
   },
   header: {
     flexGrow: 0,
@@ -15,18 +16,21 @@ export const useLayoutStyles = makeStyles({
   },
   mainContainer: {
     display: 'flex',
-    flexGrow: 1,
-    flexShrink: 1,
-    flexBasis: 'auto',
+    flexGrow: 0,
+    flexShrink: 0,
+    height: '100%',
+    overflowY: 'hidden',
   },
   main: {
     ...shorthands.padding(
       gov4GitTokens.spacingVerticalL,
       gov4GitTokens.spacingHorizontalM,
     ),
-    flexGrow: 1,
+    height: 'calc(100% - 60px)',
+    overflowY: 'auto',
+    flexGrow: 0,
     flexShrink: 1,
-    flexBasis: 'auto',
+    flexBasis: '100%',
     position: 'relative',
   },
 })