diff --git a/logback-core/src/main/java/ch/qos/logback/core/pattern/PatternLayoutBase.java b/logback-core/src/main/java/ch/qos/logback/core/pattern/PatternLayoutBase.java
index 5002241324077a807ef78e381ae583b3a8987f74..f416ecf2dc5d7544062263896df85f90f7197980 100644
--- a/logback-core/src/main/java/ch/qos/logback/core/pattern/PatternLayoutBase.java
+++ b/logback-core/src/main/java/ch/qos/logback/core/pattern/PatternLayoutBase.java
@@ -27,6 +27,9 @@ import java.util.Map;
 
 abstract public class PatternLayoutBase<E> extends LayoutBase<E> {
 
+
+    static final int INTIAL_STRING_BUILDER_SIZE = 256;
+    
     Converter<E> head;
     String pattern;
     protected PostCompileProcessor<E> postCompileProcessor;
@@ -108,7 +111,7 @@ abstract public class PatternLayoutBase<E> extends LayoutBase<E> {
     }
 
     protected String writeLoopOnConverters(E event) {
-        StringBuilder buf = new StringBuilder(128);
+        StringBuilder buf = new StringBuilder(INTIAL_STRING_BUILDER_SIZE);
         Converter<E> c = head;
         while (c != null) {
             c.write(buf, event);