diff --git a/cpp/src/strings/substring.cu b/cpp/src/strings/substring.cu
index 68080c0eb89..f712b0cb6aa 100644
--- a/cpp/src/strings/substring.cu
+++ b/cpp/src/strings/substring.cu
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2020, NVIDIA CORPORATION.
+ * Copyright (c) 2019-2021, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -43,17 +43,25 @@ namespace {
  * using the provided start, stop, and step parameters.
  */
 struct substring_fn {
-  const column_device_view d_column;
-  numeric_scalar_device_view<size_type> d_start, d_stop, d_step;
-  const int32_t* d_offsets{};
+  column_device_view const d_column;
+  numeric_scalar_device_view<size_type> const d_start;
+  numeric_scalar_device_view<size_type> const d_stop;
+  numeric_scalar_device_view<size_type> const d_step;
+  int32_t* d_offsets{};
   char* d_chars{};
 
-  __device__ cudf::size_type operator()(size_type idx)
+  __device__ void operator()(size_type idx)
   {
-    if (d_column.is_null(idx)) return 0;  // null string
-    string_view d_str = d_column.template element<string_view>(idx);
+    if (d_column.is_null(idx)) {
+      if (!d_chars) d_offsets[idx] = 0;
+      return;
+    }
+    auto const d_str  = d_column.template element<string_view>(idx);
     auto const length = d_str.length();
-    if (length == 0) return 0;  // empty string
+    if (length == 0) {
+      if (!d_chars) d_offsets[idx] = 0;
+      return;
+    }
     size_type const step = d_step.is_valid() ? d_step.value() : 1;
     auto const begin     = [&] {  // always inclusive
       // when invalid, default depends on step
@@ -88,7 +96,7 @@ struct substring_fn {
       if (d_buffer) d_buffer += from_char_utf8(*itr, d_buffer);
       itr += step;
     }
-    return bytes;
+    if (!d_chars) d_offsets[idx] = bytes;
   }
 };
 
@@ -103,42 +111,26 @@ std::unique_ptr<column> slice_strings(
   rmm::cuda_stream_view stream           = rmm::cuda_stream_default,
   rmm::mr::device_memory_resource* mr    = rmm::mr::get_current_device_resource())
 {
-  size_type strings_count = strings.size();
-  if (strings_count == 0) return make_empty_strings_column(stream, mr);
+  if (strings.is_empty()) return make_empty_strings_column(stream, mr);
 
   if (step.is_valid()) CUDF_EXPECTS(step.value(stream) != 0, "Step parameter must not be 0");
 
-  auto strings_column = column_device_view::create(strings.parent(), stream);
-  auto d_column       = *strings_column;
-  auto d_start        = get_scalar_device_view(const_cast<numeric_scalar<size_type>&>(start));
-  auto d_stop         = get_scalar_device_view(const_cast<numeric_scalar<size_type>&>(stop));
-  auto d_step         = get_scalar_device_view(const_cast<numeric_scalar<size_type>&>(step));
-
-  // copy the null mask
-  rmm::device_buffer null_mask = cudf::detail::copy_bitmask(strings.parent(), stream, mr);
-
-  // build offsets column
-  auto offsets_transformer_itr = thrust::make_transform_iterator(
-    thrust::make_counting_iterator<int32_t>(0), substring_fn{d_column, d_start, d_stop, d_step});
-  auto offsets_column = make_offsets_child_column(
-    offsets_transformer_itr, offsets_transformer_itr + strings_count, stream, mr);
-  auto d_new_offsets = offsets_column->view().data<int32_t>();
-
-  // build chars column
-  auto bytes = cudf::detail::get_value<int32_t>(offsets_column->view(), strings_count, stream);
-  auto chars_column = strings::detail::create_chars_child_column(
-    strings_count, strings.null_count(), bytes, stream, mr);
-  auto d_chars = chars_column->mutable_view().data<char>();
-  thrust::for_each_n(rmm::exec_policy(stream),
-                     thrust::make_counting_iterator<size_type>(0),
-                     strings_count,
-                     substring_fn{d_column, d_start, d_stop, d_step, d_new_offsets, d_chars});
+  auto const d_column = column_device_view::create(strings.parent(), stream);
+  auto const d_start  = get_scalar_device_view(const_cast<numeric_scalar<size_type>&>(start));
+  auto const d_stop   = get_scalar_device_view(const_cast<numeric_scalar<size_type>&>(stop));
+  auto const d_step   = get_scalar_device_view(const_cast<numeric_scalar<size_type>&>(step));
 
-  return make_strings_column(strings_count,
-                             std::move(offsets_column),
-                             std::move(chars_column),
+  auto children = make_strings_children(substring_fn{*d_column, d_start, d_stop, d_step},
+                                        strings.size(),
+                                        strings.null_count(),
+                                        stream,
+                                        mr);
+
+  return make_strings_column(strings.size(),
+                             std::move(children.first),
+                             std::move(children.second),
                              strings.null_count(),
-                             std::move(null_mask),
+                             cudf::detail::copy_bitmask(strings.parent(), stream, mr),
                              stream,
                              mr);
 }
@@ -166,25 +158,33 @@ namespace {
  * This both calculates the output size and executes the substring.
  */
 struct substring_from_fn {
-  const column_device_view d_column;
-  const cudf::detail::input_indexalator starts;
-  const cudf::detail::input_indexalator stops;
-  const int32_t* d_offsets{};
+  column_device_view const d_column;
+  cudf::detail::input_indexalator const starts;
+  cudf::detail::input_indexalator const stops;
+  int32_t* d_offsets{};
   char* d_chars{};
 
-  __device__ size_type operator()(size_type idx)
+  __device__ void operator()(size_type idx)
   {
-    if (d_column.is_null(idx)) return 0;  // null string
-    string_view d_str = d_column.template element<string_view>(idx);
+    if (d_column.is_null(idx)) {
+      if (!d_chars) d_offsets[idx] = 0;
+      return;
+    }
+    auto const d_str  = d_column.template element<string_view>(idx);
     auto const length = d_str.length();
     auto const start  = starts[idx];
-    if (start >= length) return 0;  // empty string
+    if (start >= length) {
+      if (!d_chars) d_offsets[idx] = 0;
+      return;
+    }
     auto const stop = stops[idx];
     auto const end  = (((stop < 0) || (stop > length)) ? length : stop);
 
-    string_view d_substr = d_str.substr(start, end - start);
-    if (d_chars) memcpy(d_chars + d_offsets[idx], d_substr.data(), d_substr.size_bytes());
-    return d_substr.size_bytes();
+    auto const d_substr = d_str.substr(start, end - start);
+    if (d_chars)
+      memcpy(d_chars + d_offsets[idx], d_substr.data(), d_substr.size_bytes());
+    else
+      d_offsets[idx] = d_substr.size_bytes();
   }
 };
 
@@ -212,32 +212,18 @@ std::unique_ptr<column> compute_substrings_from_fn(column_device_view const& d_c
   auto strings_count = d_column.size();
 
   // Copy the null mask
-  rmm::device_buffer null_mask{0, stream, mr};
-  if (d_column.nullable())
-    null_mask = rmm::device_buffer(
-      d_column.null_mask(), cudf::bitmask_allocation_size_bytes(strings_count), stream, mr);
-
-  // Build offsets column
-  auto offsets_transformer_itr = thrust::make_transform_iterator(
-    thrust::make_counting_iterator<size_type>(0), substring_from_fn{d_column, starts, stops});
-  auto offsets_column = cudf::strings::detail::make_offsets_child_column(
-    offsets_transformer_itr, offsets_transformer_itr + strings_count, stream, mr);
-  auto d_new_offsets = offsets_column->view().data<int32_t>();
-
-  // Build chars column
-  auto bytes = cudf::detail::get_value<int32_t>(offsets_column->view(), strings_count, stream);
-  auto chars_column =
-    cudf::strings::detail::create_chars_child_column(strings_count, null_count, bytes, stream, mr);
-  auto chars_view = chars_column->mutable_view();
-  auto d_chars    = chars_view.template data<char>();
-  thrust::for_each_n(rmm::exec_policy(stream),
-                     thrust::make_counting_iterator<cudf::size_type>(0),
-                     strings_count,
-                     substring_from_fn{d_column, starts, stops, d_new_offsets, d_chars});
+  rmm::device_buffer null_mask =
+    !d_column.nullable()
+      ? rmm::device_buffer{0, stream, mr}
+      : rmm::device_buffer(
+          d_column.null_mask(), cudf::bitmask_allocation_size_bytes(strings_count), stream, mr);
+
+  auto children = make_strings_children(
+    substring_from_fn{d_column, starts, stops}, strings_count, null_count, stream, mr);
 
   return make_strings_column(strings_count,
-                             std::move(offsets_column),
-                             std::move(chars_column),
+                             std::move(children.first),
+                             std::move(children.second),
                              null_count,
                              std::move(null_mask),
                              stream,