diff --git a/esphome/components/json/json_util.cpp b/esphome/components/json/json_util.cpp
index 40a3496981..51c0fcf9cb 100644
--- a/esphome/components/json/json_util.cpp
+++ b/esphome/components/json/json_util.cpp
@@ -8,31 +8,6 @@ namespace json {
 
 static const char *const TAG = "json";
 
-#ifdef USE_PSRAM
-// Build an allocator for the JSON Library using the RAMAllocator class
-// This is only compiled when PSRAM is enabled
-struct SpiRamAllocator : ArduinoJson::Allocator {
-  void *allocate(size_t size) override { return this->allocator_.allocate(size); }
-
-  void deallocate(void *pointer) override {
-    // ArduinoJson's Allocator interface doesn't provide the size parameter in deallocate.
-    // RAMAllocator::deallocate() requires the size, which we don't have access to here.
-    // RAMAllocator::deallocate implementation just calls free() regardless of whether
-    // the memory was allocated with heap_caps_malloc or malloc.
-    // This is safe because ESP-IDF's heap implementation internally tracks the memory region
-    // and routes free() to the appropriate heap.
-    free(pointer);  // NOLINT(cppcoreguidelines-owning-memory,cppcoreguidelines-no-malloc)
-  }
-
-  void *reallocate(void *ptr, size_t new_size) override {
-    return this->allocator_.reallocate(static_cast<uint8_t *>(ptr), new_size);
-  }
-
- protected:
-  RAMAllocator<uint8_t> allocator_{RAMAllocator<uint8_t>(RAMAllocator<uint8_t>::NONE)};
-};
-#endif
-
 std::string build_json(const json_build_t &f) {
   // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   JsonBuilder builder;
@@ -69,27 +44,6 @@ bool parse_json(const std::string &data, const json_parse_t &f) {
   // NOLINTEND(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 
-// JsonBuilder implementation
-JsonBuilder::JsonBuilder()
-    : doc_(
-#ifdef USE_PSRAM
-          [this]() {
-            auto *alloc = new SpiRamAllocator();  // NOLINT(cppcoreguidelines-owning-memory)
-            allocator_ = alloc;
-            return alloc;
-          }()
-#else
-          nullptr
-#endif
-      ) {
-}
-
-JsonBuilder::~JsonBuilder() {
-#ifdef USE_PSRAM
-  delete static_cast<SpiRamAllocator *>(allocator_);  // NOLINT(cppcoreguidelines-owning-memory)
-#endif
-}
-
 std::string JsonBuilder::serialize() {
   if (doc_.overflowed()) {
     ESP_LOGE(TAG, "JSON document overflow");
diff --git a/esphome/components/json/json_util.h b/esphome/components/json/json_util.h
index 8eac87b10a..69b809ec49 100644
--- a/esphome/components/json/json_util.h
+++ b/esphome/components/json/json_util.h
@@ -13,6 +13,31 @@
 namespace esphome {
 namespace json {
 
+#ifdef USE_PSRAM
+// Build an allocator for the JSON Library using the RAMAllocator class
+// This is only compiled when PSRAM is enabled
+struct SpiRamAllocator : ArduinoJson::Allocator {
+  void *allocate(size_t size) override { return allocator_.allocate(size); }
+
+  void deallocate(void *ptr) override {
+    // ArduinoJson's Allocator interface doesn't provide the size parameter in deallocate.
+    // RAMAllocator::deallocate() requires the size, which we don't have access to here.
+    // RAMAllocator::deallocate implementation just calls free() regardless of whether
+    // the memory was allocated with heap_caps_malloc or malloc.
+    // This is safe because ESP-IDF's heap implementation internally tracks the memory region
+    // and routes free() to the appropriate heap.
+    free(ptr);  // NOLINT(cppcoreguidelines-owning-memory,cppcoreguidelines-no-malloc)
+  }
+
+  void *reallocate(void *ptr, size_t new_size) override {
+    return allocator_.reallocate(static_cast<uint8_t *>(ptr), new_size);
+  }
+
+ protected:
+  RAMAllocator<uint8_t> allocator_{RAMAllocator<uint8_t>::NONE};
+};
+#endif
+
 /// Callback function typedef for parsing JsonObjects.
 using json_parse_t = std::function<bool(JsonObject)>;
 
@@ -28,9 +53,6 @@ bool parse_json(const std::string &data, const json_parse_t &f);
 /// Builder class for creating JSON documents without lambdas
 class JsonBuilder {
  public:
-  JsonBuilder();
-  ~JsonBuilder();
-
   JsonObject root() {
     if (!root_created_) {
       root_ = doc_.to<JsonObject>();
@@ -42,13 +64,14 @@ class JsonBuilder {
   std::string serialize();
 
  private:
+#ifdef USE_PSRAM
+  SpiRamAllocator allocator_;
+  JsonDocument doc_{&allocator_};
+#else
   JsonDocument doc_;
+#endif
   JsonObject root_;
   bool root_created_{false};
-  // Allocator must be last member to ensure it's destroyed after doc_
-#ifdef USE_PSRAM
-  void *allocator_{nullptr};  // Will store SpiRamAllocator*, managed in cpp file
-#endif
 };
 
 }  // namespace json