diff --git a/doc/dev-notes.txt b/doc/dev-notes.txt
index 98e9dc17..601aa852 100644
--- a/doc/dev-notes.txt
+++ b/doc/dev-notes.txt
@@ -95,7 +95,7 @@
 
 * Delete all scheduled builds that are not already building:
 
-  delete from builds where finished = 0 and not exists (select 1 from buildschedulinginfo s where s.id = builds.id and busy = 1);
+  delete from builds where finished = 0 and not exists (select 1 from buildschedulinginfo s where s.id = builds.id and busy != 0);
 
 
 * select x.project, x.jobset, x.job, x.system, x.id, x.timestamp, r.buildstatus, b.id, b.timestamp
diff --git a/src/hydra-queue-runner/build-remote.cc b/src/hydra-queue-runner/build-remote.cc
index 55958b6c..dccc4469 100644
--- a/src/hydra-queue-runner/build-remote.cc
+++ b/src/hydra-queue-runner/build-remote.cc
@@ -122,7 +122,8 @@ static void copyClosureTo(std::timed_mutex & sendMutex, ref<Store> destStore,
 void State::buildRemote(ref<Store> destStore,
     Machine::ptr machine, Step::ptr step,
     unsigned int maxSilentTime, unsigned int buildTimeout, unsigned int repeats,
-    RemoteResult & result, std::shared_ptr<ActiveStep> activeStep)
+    RemoteResult & result, std::shared_ptr<ActiveStep> activeStep,
+    std::function<void(StepState)> updateStep)
 {
     assert(BuildResult::TimedOut == 8);
 
@@ -140,6 +141,8 @@ void State::buildRemote(ref<Store> destStore,
 
     try {
 
+        updateStep(ssConnecting);
+
         Child child;
         openConnection(machine, tmpDir, logFD.get(), child);
 
@@ -204,6 +207,8 @@ void State::buildRemote(ref<Store> destStore,
            outputs of the input derivations. On Nix > 1.9, we only need to
            copy the immediate sources of the derivation and the required
            outputs of the input derivations. */
+        updateStep(ssSendingInputs);
+
         PathSet inputs;
         BasicDerivation basicDrv(step->drv);
 
@@ -260,6 +265,8 @@ void State::buildRemote(ref<Store> destStore,
         /* Do the build. */
         printMsg(lvlDebug, format("building ‘%1%’ on ‘%2%’") % step->drvPath % machine->sshName);
 
+        updateStep(ssBuilding);
+
         if (sendDerivation)
             to << cmdBuildPaths << PathSet({step->drvPath});
         else
@@ -371,6 +378,8 @@ void State::buildRemote(ref<Store> destStore,
 
         /* Copy the output paths. */
         if (/* machine->sshName != "localhost" */ true) {
+            updateStep(ssReceivingOutputs);
+
             MaintainCount<counter> mc(nrStepsCopyingFrom);
 
             auto now1 = std::chrono::steady_clock::now();
diff --git a/src/hydra-queue-runner/builder.cc b/src/hydra-queue-runner/builder.cc
index ceaa252e..d9a7cbbb 100644
--- a/src/hydra-queue-runner/builder.cc
+++ b/src/hydra-queue-runner/builder.cc
@@ -195,10 +195,16 @@ State::StepResult State::doBuildStep(nix::ref<Store> destStore,
             txn.commit();
         }
 
+        auto updateStep = [&](StepState stepState) {
+            pqxx::work txn(*conn);
+            updateBuildStep(txn, buildId, stepNr, stepState);
+            txn.commit();
+        };
+
         /* Do the build. */
         try {
             /* FIXME: referring builds may have conflicting timeouts. */
-            buildRemote(destStore, machine, step, maxSilentTime, buildTimeout, repeats, result, activeStep);
+            buildRemote(destStore, machine, step, maxSilentTime, buildTimeout, repeats, result, activeStep, updateStep);
         } catch (NoTokens & e) {
             result.stepStatus = bsNarSizeLimitExceeded;
         } catch (Error & e) {
@@ -213,8 +219,10 @@ State::StepResult State::doBuildStep(nix::ref<Store> destStore,
             }
         }
 
-        if (result.stepStatus == bsSuccess)
+        if (result.stepStatus == bsSuccess) {
+            updateStep(ssPostProcessing);
             res = getBuildOutput(destStore, ref<FSAccessor>(result.accessor), step->drv);
+        }
 
         result.accessor = 0;
         result.tokens = 0;
diff --git a/src/hydra-queue-runner/hydra-queue-runner.cc b/src/hydra-queue-runner/hydra-queue-runner.cc
index 7339d603..85635823 100644
--- a/src/hydra-queue-runner/hydra-queue-runner.cc
+++ b/src/hydra-queue-runner/hydra-queue-runner.cc
@@ -271,7 +271,7 @@ void State::clearBusy(Connection & conn, time_t stopTime)
 {
     pqxx::work txn(conn);
     txn.parameterized
-        ("update BuildSteps set busy = 0, status = $1, stopTime = $2 where busy = 1")
+        ("update BuildSteps set busy = 0, status = $1, stopTime = $2 where busy != 0")
         ((int) bsAborted)
         (stopTime, stopTime != 0).exec();
     txn.commit();
@@ -317,6 +317,18 @@ unsigned int State::createBuildStep(pqxx::work & txn, time_t startTime, BuildID
 }
 
 
+void State::updateBuildStep(pqxx::work & txn, BuildID buildId, unsigned int stepNr, StepState stepState)
+{
+    if (txn.parameterized
+        ("update BuildSteps set busy = $1 where build = $2 and stepnr = $3 and busy != 0 and status is null")
+        ((int) stepState)
+        (buildId)
+        (stepNr)
+        .exec().affected_rows() != 1)
+        throw Error("step %d of build %d is in an unexpected state", stepNr, buildId);
+}
+
+
 void State::finishBuildStep(pqxx::work & txn, const RemoteResult & result,
     BuildID buildId, unsigned int stepNr, const std::string & machine)
 {
@@ -892,7 +904,7 @@ void State::run(BuildID buildOne)
                 for (auto & step : steps) {
                     printMsg(lvlError, format("cleaning orphaned step %d of build %d") % step.second % step.first);
                     txn.parameterized
-                        ("update BuildSteps set busy = 0, status = $1 where build = $2 and stepnr = $3 and busy = 1")
+                        ("update BuildSteps set busy = 0, status = $1 where build = $2 and stepnr = $3 and busy != 0")
                         ((int) bsAborted)
                         (step.first)
                         (step.second).exec();
diff --git a/src/hydra-queue-runner/state.hh b/src/hydra-queue-runner/state.hh
index 543a36e3..fc17a116 100644
--- a/src/hydra-queue-runner/state.hh
+++ b/src/hydra-queue-runner/state.hh
@@ -41,6 +41,16 @@ typedef enum {
 } BuildStatus;
 
 
+typedef enum {
+    ssPreparing = 1,
+    ssConnecting = 10,
+    ssSendingInputs = 20,
+    ssBuilding = 30,
+    ssReceivingOutputs = 40,
+    ssPostProcessing = 50,
+} StepState;
+
+
 struct RemoteResult
 {
     BuildStatus stepStatus = bsAborted;
@@ -464,6 +474,8 @@ private:
         const std::string & machine, BuildStatus status, const std::string & errorMsg = "",
         BuildID propagatedFrom = 0);
 
+    void updateBuildStep(pqxx::work & txn, BuildID buildId, unsigned int stepNr, StepState stepState);
+
     void finishBuildStep(pqxx::work & txn, const RemoteResult & result, BuildID buildId, unsigned int stepNr,
         const std::string & machine);
 
@@ -518,7 +530,8 @@ private:
         Machine::ptr machine, Step::ptr step,
         unsigned int maxSilentTime, unsigned int buildTimeout,
         unsigned int repeats,
-        RemoteResult & result, std::shared_ptr<ActiveStep> activeStep);
+        RemoteResult & result, std::shared_ptr<ActiveStep> activeStep,
+        std::function<void(StepState)> updateStep);
 
     void markSucceededBuild(pqxx::work & txn, Build::ptr build,
         const BuildOutput & res, bool isCachedBuild, time_t startTime, time_t stopTime);
diff --git a/src/lib/Hydra/Controller/Root.pm b/src/lib/Hydra/Controller/Root.pm
index e6a503a1..8e53dad7 100644
--- a/src/lib/Hydra/Controller/Root.pm
+++ b/src/lib/Hydra/Controller/Root.pm
@@ -53,7 +53,7 @@ sub begin :Private {
 
     if (scalar(@args) == 0 || $args[0] ne "static") {
         $c->stash->{nrRunningBuilds} = dbh($c)->selectrow_array(
-            "select count(distinct build) from buildsteps where busy = 1");
+            "select count(distinct build) from buildsteps where busy != 0");
         $c->stash->{nrQueuedBuilds} = $c->model('DB::Builds')->search({ finished => 0 })->count();
     }
 
@@ -145,7 +145,7 @@ sub status_GET {
     $self->status_ok(
         $c,
         entity => [$c->model('DB::Builds')->search(
-            { "buildsteps.busy" => 1 },
+            { "buildsteps.busy" => { '!=', 0 } },
             { order_by => ["globalpriority DESC", "id"],
               join => "buildsteps",
               columns => [@buildListColumns]
@@ -193,7 +193,7 @@ sub machines :Local Args(0) {
     $c->stash->{steps} = dbh($c)->selectall_arrayref(
         "select build, stepnr, s.system as system, s.drvpath as drvpath, machine, s.starttime as starttime, project, jobset, job " .
         "from BuildSteps s join Builds b on s.build = b.id " .
-        "where busy = 1 order by machine, stepnr",
+        "where busy != 0 order by machine, stepnr",
         { Slice => {} });
     $c->stash->{template} = 'machine-status.tt';
 }
diff --git a/src/root/build.tt b/src/root/build.tt
index 8b7171a9..ee0dcaa2 100644
--- a/src/root/build.tt
+++ b/src/root/build.tt
@@ -29,7 +29,7 @@ END;
     </thead>
     <tbody>
       [% FOREACH step IN steps %]
-        [% IF ( type == "All" ) || ( type == "Failed" && step.busy == 0 && step.status != 0 ) || ( type == "Running" && step.busy == 1 ) %]
+        [% IF ( type == "All" ) || ( type == "Failed" && step.busy == 0 && step.status != 0 ) || ( type == "Running" && step.busy != 0 ) %]
           [% has_log = seen.${step.drvpath} ? 0 : buildStepLogExists(step);
              seen.${step.drvpath} = 1;
              log = c.uri_for('/build' build.id 'nixlog' step.stepnr); %]
@@ -55,10 +55,24 @@ END;
                    INCLUDE renderDuration duration = curTime - step.starttime;
                  END %]
             </td>
-            <td>[% IF step.busy == 1 || ((step.machine || step.starttime) && (step.status == 0 || step.status == 1 || step.status == 3 || step.status == 4 || step.status == 7)); INCLUDE renderMachineName machine=step.machine; ELSE; "<em>n/a</em>"; END %]</td>
+            <td>[% IF step.busy != 0 || ((step.machine || step.starttime) && (step.status == 0 || step.status == 1 || step.status == 3 || step.status == 4 || step.status == 7)); INCLUDE renderMachineName machine=step.machine; ELSE; "<em>n/a</em>"; END %]</td>
             <td class="step-status">
-              [% IF step.busy == 1 %]
-                <strong>Building</strong>
+              [% IF step.busy != 0 %]
+                [% IF step.busy == 1 %]
+                  <strong>Preparing</strong>
+                [% ELSIF step.busy == 10 %]
+                  <strong>Connecting</strong>
+                [% ELSIF step.busy == 20 %]
+                  <strong>Sending inputs</strong>
+                [% ELSIF step.busy == 30 %]
+                  <strong>Building</strong>
+                [% ELSIF step.busy == 40 %]
+                  <strong>Receiving outputs</strong>
+                [% ELSIF step.busy == 50 %]
+                  <strong>Post-processing</strong>
+                [% ELSE %]
+                  <strong>Unknown state</strong>
+                [% END %]
               [% ELSIF step.status == 0 %]
                 [% IF step.isnondeterministic %]
                   <span class="warn">Succeeded with non-determistic result</span>
diff --git a/src/root/machine-status.tt b/src/root/machine-status.tt
index 7c6d1f2b..4195c178 100644
--- a/src/root/machine-status.tt
+++ b/src/root/machine-status.tt
@@ -42,7 +42,7 @@
             <td><tt>[% INCLUDE renderFullJobName project=step.project jobset=step.jobset job=step.job %]</tt></td>
             <td><tt>[% step.system %]</tt></td>
             <td><a href="[% c.uri_for('/build' step.build) %]">[% step.build %]</a></td>
-            <td><a class="row-link" href="[% c.uri_for('/build' step.build 'nixlog' step.stepnr 'tail') %]">[% step.stepnr %]</a></td>
+            <td>[% IF step.busy >= 30 %]<a class="row-link" href="[% c.uri_for('/build' step.build 'nixlog' step.stepnr 'tail') %]">[% step.stepnr %]</a>[% ELSE; step.stepnr; END %]</td>
             <td><tt>[% step.drvpath.match('-(.*)').0 %]</tt></td>
             <td style="width: 10em">[% INCLUDE renderDuration duration = curTime - step.starttime %] </td>
           </tr>
diff --git a/src/sql/hydra.sql b/src/sql/hydra.sql
index d1c3ee37..4c8710b8 100644
--- a/src/sql/hydra.sql
+++ b/src/sql/hydra.sql
@@ -272,6 +272,13 @@ create table BuildSteps (
 
     drvPath       text,
 
+    -- 0 = not busy
+    -- 1 = building
+    -- 2 = preparing to build
+    -- 3 = connecting
+    -- 4 = sending inputs
+    -- 5 = receiving outputs
+    -- 6 = analysing build result
     busy          integer not null,
 
     status        integer, -- see Builds.buildStatus
@@ -648,7 +655,7 @@ create index IndexBuildInputsOnDependency on BuildInputs(dependency);
 create index IndexBuildMetricsOnJobTimestamp on BuildMetrics(project, jobset, job, timestamp desc);
 create index IndexBuildProducstOnBuildAndType on BuildProducts(build, type);
 create index IndexBuildProductsOnBuild on BuildProducts(build);
-create index IndexBuildStepsOnBusy on BuildSteps(busy) where busy = 1;
+create index IndexBuildStepsOnBusy on BuildSteps(busy) where busy != 0;
 create index IndexBuildStepsOnDrvPath on BuildSteps(drvpath);
 create index IndexBuildStepsOnPropagatedFrom on BuildSteps(propagatedFrom) where propagatedFrom is not null;
 create index IndexBuildStepsOnStopTime on BuildSteps(stopTime desc) where startTime is not null and stopTime is not null;
diff --git a/src/sql/upgrade-56.sql b/src/sql/upgrade-56.sql
new file mode 100644
index 00000000..6b9449aa
--- /dev/null
+++ b/src/sql/upgrade-56.sql
@@ -0,0 +1,2 @@
+drop index IndexBuildStepsOnBusy;
+create index IndexBuildStepsOnBusy on BuildSteps(busy) where busy != 0;