diff --git a/Dockerfile b/Dockerfile
index e3a7b110..6f2f646b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,10 +1,16 @@
+# Builds all XEPs by default, HTML & PDF
+# docker build . --build-arg NCORES=X --build-arg TARGETS="target1 target2"
+# from Dockerfile.base
 FROM xmppxsf/xeps-base:latest
 
+ARG NCORES=1
+ARG TARGETS="html pdf"
+
 COPY *.xml xep.* *.css *.xsl *.js *.xsl Makefile /src/
 COPY resources/*.pdf /src/resources/
 
 WORKDIR /src
-RUN OUTDIR=/var/www/html/extensions/ make -j5 html pdf
+RUN OUTDIR=/var/www/html/extensions/ make -j$NCORES $TARGETS
 
 EXPOSE 80
 
diff --git a/Dockerfile.base b/Dockerfile.base
index 08156da4..7a605c0a 100644
--- a/Dockerfile.base
+++ b/Dockerfile.base
@@ -1,3 +1,7 @@
+# Base docker image for building XEPs
+# Sets up directories and dependencies
+# docker build . -t xmppxsf/xeps-base -f Dockerfile.base
+
 FROM debian:8
 MAINTAINER XSF Editors <editor@xmpp.org>