diff --git a/.ci/travis/docker_image/script.sh b/.ci/travis/docker_image/script.sh
index 21995e9ff0c..edcb2fe500a 100755
--- a/.ci/travis/docker_image/script.sh
+++ b/.ci/travis/docker_image/script.sh
@@ -17,48 +17,79 @@
 
 set -e
 
-mkdir -p "${CCACHE_DIR}"
+# test if ccache dir exists (coming from Travis cache)
+[[ -d ${CCACHE_DIR} ]] && echo "cache directory (${CCACHE_DIR}) exists" || mkdir -p "${CCACHE_DIR}"
 
 # copy ccache dir within QGIS source so it can be accessed from docker
-cp -r ${CCACHE_DIR} ${TRAVIS_BUILD_DIR}/.ccache_image_build
+cp -r ${CCACHE_DIR}/. ${TRAVIS_BUILD_DIR}/.ccache_image_build
+
+echo "Cache directory size: "$(du -h --max-depth=0 ${TRAVIS_BUILD_DIR}/.ccache_image_build)
+
+# calculate timeouts
+CURRENT_TIME=$(date +%s)
+TIMEOUT=$((( TRAVIS_AVAILABLE_TIME - TRAVIS_UPLOAD_TIME ) * 60 - CURRENT_TIME + TRAVIS_TIMESTAMP))
+#TIMEOUT=$(( TIMEOUT < 300 ? 300 : TIMEOUT ))
+echo "Timeout: ${TIMEOUT}s"
+
 # building docker images
-DIR=$(git rev-parse --show-toplevel)/.docker
-pushd "${DIR}"
+pushd "${TRAVIS_BUILD_DIR}/.docker"
 echo "${bold}Building QGIS Docker image '${DOCKER_TAG}'...${endbold}"
-docker build --build-arg DOCKER_TAG="${DOCKER_TAG}" \
+DOCKER_BUILD_ARGS="--build-arg DOCKER_TAG=${DOCKER_TAG} \
+                   --build-arg BUILD_TIMEOUT=${TIMEOUT} \
+                   --build-arg CC --build-arg CXX"
+docker build ${DOCKER_BUILD_ARGS} \
              --cache-from "qgis/qgis:${DOCKER_TAG}" \
-             -t "qgis/qgis:${DOCKER_TAG}" \
-             --build-arg CC --build-arg CXX \
+             -t "qgis/qgis:BUILDER" \
              -f qgis.dockerfile ..
-echo "${bold}Pushing image to docker hub...${endbold}"
-docker login -u="$DOCKER_USERNAME" -p="$DOCKER_PASSWORD"
-docker push "qgis/qgis:${DOCKER_TAG}"
+
+docker run --name qgis_container qgis/qgis:BUILDER /bin/true
+
 echo "Copy build cache from Docker container to Travis cache directory"
 rm -rf "${CCACHE_DIR:?}/"*
-docker run --name qgis_container qgis/qgis:${DOCKER_TAG} /bin/true
-docker cp qgis_container:/usr/src/.ccache_image_build ${CCACHE_DIR}
-docker rm qgis_container
-popd
-echo "Trigger build of PyQGIS Documentation"
-if [[ ${TRIGGER_PYQGIS_DOC} =~ ^TRUE$ ]]; then
-  body='{
-    "request": {
-      "branch":"master",
-      "message": "Trigger PyQGIS doc build after release of new Docker image as __DOCKER_TAG__",
-      "config": {
-        "merge_mode": "deep_merge",
-        "matrix": {
-          "include": {
-            "env": ["QGIS_VERSION_BRANCH=__QGIS_VERSION_BRANCH__"]
+mkdir -p ${CCACHE_DIR}
+docker cp qgis_container:/QGIS/.ccache_image_build/. ${CCACHE_DIR}
+
+docker cp qgis_container:/QGIS/build_exit_value ${HOME}/build_exit_value
+
+if [[ $(cat ${HOME}/build_exit_value) == "TIMEOUT" ]]; then
+  echo "Build timeout, not pushing image or triggering PyQGIS docs"
+  exit 1
+else
+  echo "${bold}Finalize image…${endbold}"
+  # enable experimental features in Docker to squash
+  echo '{ "experimental": true}' | sudo tee /etc/docker/daemon.json
+  sudo service docker restart
+  docker build ${DOCKER_BUILD_ARGS} \
+             --cache-from "qgis/qgis:BUILDER" \
+             --squash \
+             -t "qgis/qgis:${DOCKER_TAG}" \
+             -f qgis.dockerfile ..
+
+  echo "${bold}Pushing image to docker hub…${endbold}"
+  docker login -u="$DOCKER_USERNAME" -p="$DOCKER_PASSWORD"
+  docker push "qgis/qgis:${DOCKER_TAG}"
+
+  echo "Trigger build of PyQGIS Documentation…"
+  if [[ ${TRIGGER_PYQGIS_DOC} =~ ^TRUE$ ]]; then
+    body='{
+      "request": {
+        "branch":"master",
+        "message": "Trigger PyQGIS doc build after release of new Docker image as __DOCKER_TAG__",
+        "config": {
+          "merge_mode": "deep_merge",
+          "matrix": {
+            "include": {
+              "env": ["QGIS_VERSION_BRANCH=__QGIS_VERSION_BRANCH__"]
+            }
           }
         }
       }
-    }
-  }'
-  body=$(sed "s/__QGIS_VERSION_BRANCH__/${TRAVIS_BRANCH}/; s/__DOCKER_TAG__/${DOCKER_TAG}/" <<< $body)
-  curl -s -X POST -H "Content-Type: application/json" -H "Accept: application/json" \
-    -H "Travis-API-Version: 3" -H "Authorization: token $TRAVIS_TOKEN" -d "$body" \
-    https://api.travis-ci.org/repo/qgis%2Fpyqgis/requests
-else
-  echo "skipped from configuration"
+    }'
+    body=$(sed "s/__QGIS_VERSION_BRANCH__/${TRAVIS_BRANCH}/; s/__DOCKER_TAG__/${DOCKER_TAG}/" <<< $body)
+    curl -s -X POST -H "Content-Type: application/json" -H "Accept: application/json" \
+      -H "Travis-API-Version: 3" -H "Authorization: token $TRAVIS_TOKEN" -d "$body" \
+      https://api.travis-ci.org/repo/qgis%2Fpyqgis/requests
+  else
+    echo "skipped from configuration"
+  fi
 fi
diff --git a/.docker/qgis.dockerfile b/.docker/qgis.dockerfile
index f6607af213f..e71f6b6aebb 100644
--- a/.docker/qgis.dockerfile
+++ b/.docker/qgis.dockerfile
@@ -1,27 +1,32 @@
 
-# CACHE_TAG is provided by Docker cloud
 # see https://docs.docker.com/docker-cloud/builds/advanced/
 # using ARG in FROM requires min v17.05.0-ce
 ARG DOCKER_TAG=latest
 
-FROM  qgis/qgis3-build-deps:${DOCKER_TAG}
+FROM  qgis/qgis3-build-deps:${DOCKER_TAG} AS BUILDER
 MAINTAINER Denis Rouzaud <denis@opengis.ch>
 
 LABEL Description="Docker container with QGIS" Vendor="QGIS.org" Version="1.1"
 
+# build timeout in seconds, so no timeout by default
+ARG BUILD_TIMEOUT=360000
+
 ARG CC=/usr/lib/ccache/clang
 ARG CXX=/usr/lib/ccache/clang++
 ENV LANG=C.UTF-8
 
-COPY . /usr/src/QGIS
+COPY . /QGIS
 
 # If this directory is changed, also adapt script.sh which copies the directory
-RUN mkdir -p /usr/src/.ccache_image_build
-ENV CCACHE_DIR=/usr/src/.ccache_image_build
+# if ccache directory is not provided with the source
+RUN mkdir -p /QGIS/.ccache_image_build
+ENV CCACHE_DIR=/QGIS/.ccache_image_build
 RUN ccache -M 1G
 RUN ccache -s
 
-WORKDIR /usr/src/QGIS/build
+RUN echo "ccache_dir: "$(du -h --max-depth=0 ${CCACHE_DIR})
+
+WORKDIR /QGIS/build
 
 RUN cmake \
   -GNinja \
@@ -42,13 +47,18 @@ RUN cmake \
   -DWITH_APIDOC=OFF \
   -DWITH_ASTYLE=OFF \
   -DQT5_3DEXTRA_LIBRARY="/usr/lib/x86_64-linux-gnu/libQt53DExtras.so" \
-  -DQT5_3DEXTRA_INCLUDE_DIR="/usr/src/QGIS/external/qt3dextra-headers" \
-  -DCMAKE_PREFIX_PATH="/usr/src/QGIS/external/qt3dextra-headers/cmake" \
+  -DQT5_3DEXTRA_INCLUDE_DIR="/QGIS/external/qt3dextra-headers" \
+  -DCMAKE_PREFIX_PATH="/QGIS/external/qt3dextra-headers/cmake" \
  .. \
- && ninja install \
- && rm -rf /usr/src/QGIS
+ && echo "Timeout: ${BUILD_TIMEOUT}s" \
+ && SUCCESS=OK \
+ && timeout ${BUILD_TIMEOUT}s ninja install || SUCCESS=TIMEOUT \
+ && echo "$SUCCESS" > /QGIS/build_exit_value
 
 ################################################################################
+ARG DELETE_CACHE=FALSE
+RUN if [[ ${DELETE_CACHE} == TRUE ]]; then rm /QGIS; fi
+
 # Python testing environment setup
 
 # Add QGIS test runner
diff --git a/.travis.yml b/.travis.yml
index 82d3f515d05..4a52250c441 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -18,7 +18,7 @@ env:
     - TRAVIS_TIMESTAMP=$(date +%s)
     - TRAVIS_AVAILABLE_TIME=150 # in minutes
     - TRAVIS_UPLOAD_TIME=5 # time considered to start the machine and the container (minutes)
-    # Docker hub username and passowrd
+    # Docker hub username and password
     - secure: "b7eMDIolaAnq1voGKC1ez7Kcf+/A0WZDJEHBvNwk2KubBfrGOE83GMDrFNF4NqjIprqIAvVKj+TrX1ckCvs24re3IqUJo71TaF1IgxzDDPwSsmNh5UMmvZkeiJys9bWjqDO9wYR5ietNmIE18qyMc8ToJk8oKm6AXuAG2n6znmM="
     - secure: "PHCp7F3nApp38Mz6b4/OLxgfBiikRGzPQDHg3R5LX+SQOll24c/DMtwpPwizNuFEiCFcRmJ9uc1t0HWEerIZe5uqm7AtE/nMXBsvDZ+hj4Tz/fEBF98a1k4WLYheN1exFidVkJgdAeiwMOOUQXw5KuIX62bxBdzsdcd0QGwxiXo="
     # Travis Token to create PyQGIS Documentation Travis build after Docker push
@@ -60,7 +60,7 @@ matrix:
       addons:
         apt:
           sources:
-           # - sourceline: 'ppa:jonathonf/backports'  # silversearcher-ag backport
+          # - sourceline: 'ppa:jonathonf/backports'  # silversearcher-ag backport
           packages:
             - doxygen
             - graphviz
@@ -105,6 +105,7 @@ matrix:
       name: bionic docker build 🐳
       if: repo = qgis/QGIS AND (tag IS PRESENT OR type = cron)
       services: docker
+      sudo: required # required to restart Docker Daemon with experimental features
       env:
         - TRAVIS_CONFIG=docker_image
         - CCACHE_DIR=${HOME}/.ccache_docker_build_bionic
@@ -121,6 +122,7 @@ matrix:
       name: disco docker build 💃
       if: repo = qgis/QGIS AND (tag IS PRESENT OR type = cron)
       services: docker
+      sudo: required # required to restart Docker Daemon with experimental features
       env:
         - TRAVIS_CONFIG=docker_image
         - CCACHE_DIR=${HOME}/.ccache_docker_build_disco