diff --git a/app/controllers/root_controller.rb b/app/controllers/root_controller.rb
index aa78ee3d0..febfb25d1 100644
--- a/app/controllers/root_controller.rb
+++ b/app/controllers/root_controller.rb
@@ -20,11 +20,7 @@ class RootController < ApplicationController
 
     all_champs = TypeDeChamp.type_champs
       .map { |name, _| TypeDeChamp.new(type_champ: name, libelle: name, description: description, mandatory: true) }
-      .map { |type_de_champ| ChampPublic.new(type_de_champ: type_de_champ) }
-      .map.with_index do |champ, i|
-        champ.id = i
-        champ
-      end
+      .map.with_index { |type_de_champ, i| type_de_champ.champ.build(id: i) }
 
     all_champs
       .select { |champ| champ.type_champ == 'header_section' }
diff --git a/app/models/champ.rb b/app/models/champ.rb
index e4e1555b8..4daf0e05d 100644
--- a/app/models/champ.rb
+++ b/app/models/champ.rb
@@ -1,6 +1,8 @@
 class Champ < ActiveRecord::Base
+  self.inheritance_column = :_type_disabled
+
   belongs_to :dossier, touch: true
-  belongs_to :type_de_champ
+  belongs_to :type_de_champ, inverse_of: :champ
   has_many :commentaires
 
   delegate :libelle, :type_champ, :order_place, :mandatory, :description, :drop_down_list, to: :type_de_champ
@@ -10,11 +12,21 @@ class Champ < ActiveRecord::Base
   before_save :multiple_select_to_string, if: Proc.new { type_champ == 'multiple_drop_down_list' }
 
   scope :updated_since?, -> (date) { where('champs.updated_at > ?', date) }
+  scope :public_only, -> { where.not(type: 'ChampPrivate').or(where(private: [false, nil])) }
+  scope :private_only, -> { where(type: 'ChampPrivate').or(where(private: true)) }
 
   def mandatory?
     mandatory
   end
 
+  def public?
+    !private?
+  end
+
+  def private?
+    super || type == 'ChampPrivate'
+  end
+
   def same_hour? num
     same_date? num, '%H'
   end
diff --git a/app/models/champ_private.rb b/app/models/champ_private.rb
deleted file mode 100644
index 118e58415..000000000
--- a/app/models/champ_private.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-class ChampPrivate < Champ
-end
diff --git a/app/models/champ_public.rb b/app/models/champ_public.rb
deleted file mode 100644
index c922614ae..000000000
--- a/app/models/champ_public.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-class ChampPublic < Champ
-end
diff --git a/app/models/dossier.rb b/app/models/dossier.rb
index 6c09b5328..5fede6a93 100644
--- a/app/models/dossier.rb
+++ b/app/models/dossier.rb
@@ -20,8 +20,8 @@ class Dossier < ActiveRecord::Base
   has_many :cerfa, dependent: :destroy
 
   has_many :pieces_justificatives, dependent: :destroy
-  has_many :champs, class_name: 'ChampPublic', dependent: :destroy
-  has_many :champs_private, class_name: 'ChampPrivate', dependent: :destroy
+  has_many :champs, -> { public_only }, dependent: :destroy
+  has_many :champs_private, -> { private_only }, class_name: 'Champ', dependent: :destroy
   has_many :quartier_prioritaires, dependent: :destroy
   has_many :cadastres, dependent: :destroy
   has_many :commentaires, dependent: :destroy
@@ -89,12 +89,8 @@ class Dossier < ActiveRecord::Base
   end
 
   def build_default_champs
-    procedure.types_de_champ.all.each do |type_de_champ|
-      ChampPublic.create(type_de_champ: type_de_champ, dossier: self)
-    end
-
-    procedure.types_de_champ_private.all.each do |type_de_champ|
-      ChampPrivate.create(type_de_champ: type_de_champ, dossier: self)
+    procedure.all_types_de_champ.each do |type_de_champ|
+      type_de_champ.champ.create(dossier: self)
     end
   end
 
diff --git a/app/models/procedure.rb b/app/models/procedure.rb
index 0d81f0a3a..7cf0c3d67 100644
--- a/app/models/procedure.rb
+++ b/app/models/procedure.rb
@@ -62,6 +62,10 @@ class Procedure < ActiveRecord::Base
     types_de_champ_private.order(:order_place)
   end
 
+  def all_types_de_champ
+    types_de_champ + types_de_champ_private
+  end
+
   def self.active id
     publiees.find(id)
   end
diff --git a/app/models/type_de_champ.rb b/app/models/type_de_champ.rb
index 86747bc5a..4a792d1cd 100644
--- a/app/models/type_de_champ.rb
+++ b/app/models/type_de_champ.rb
@@ -24,7 +24,15 @@ class TypeDeChamp < ActiveRecord::Base
 
   belongs_to :procedure
 
-  has_many :champ, dependent: :destroy
+  has_many :champ, inverse_of: :type_de_champ, dependent: :destroy do
+    def build(params = {})
+      super(params.merge(proxy_association.owner.params_for_champ))
+    end
+
+    def create(params = {})
+      super(params.merge(proxy_association.owner.params_for_champ))
+    end
+  end
   has_one :drop_down_list
 
   accepts_nested_attributes_for :drop_down_list
@@ -34,6 +42,12 @@ class TypeDeChamp < ActiveRecord::Base
 
   before_validation :check_mandatory
 
+  def params_for_champ
+    {
+      private: private?
+    }
+  end
+
   def self.type_de_champs_list_fr
     type_champs.map { |champ| [I18n.t("activerecord.attributes.type_de_champ.type_champs.#{champ.last}"), champ.first] }
   end
@@ -46,4 +60,12 @@ class TypeDeChamp < ActiveRecord::Base
     self.mandatory = false if %w(header_section explication).include?(self.type_champ)
     true
   end
+
+  def private?
+    type == 'TypeDeChampPrivate'
+  end
+
+  def public?
+    !private?
+  end
 end
diff --git a/app/serializers/champ_private_serializer.rb b/app/serializers/champ_private_serializer.rb
deleted file mode 100644
index b26cf274f..000000000
--- a/app/serializers/champ_private_serializer.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-class ChampPrivateSerializer < ActiveModel::Serializer
-  attributes :value
-
-  has_one :type_de_champ
-end
diff --git a/app/serializers/champ_public_serializer.rb b/app/serializers/champ_public_serializer.rb
deleted file mode 100644
index 66806c982..000000000
--- a/app/serializers/champ_public_serializer.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-class ChampPublicSerializer < ActiveModel::Serializer
-  attributes :value
-
-  has_one :type_de_champ
-end
diff --git a/app/serializers/champ_serializer.rb b/app/serializers/champ_serializer.rb
new file mode 100644
index 000000000..981c2b9cc
--- /dev/null
+++ b/app/serializers/champ_serializer.rb
@@ -0,0 +1,5 @@
+class ChampSerializer < ActiveModel::Serializer
+  attributes :value
+
+  has_one :type_de_champ
+end
diff --git a/app/views/admin/types_de_champ/_fields.html.haml b/app/views/admin/types_de_champ/_fields.html.haml
index 9e651454b..bbadc32d8 100644
--- a/app/views/admin/types_de_champ/_fields.html.haml
+++ b/app/views/admin/types_de_champ/_fields.html.haml
@@ -21,7 +21,7 @@
         = fff.hidden_field :id
 
 
-    - hide_mandatory = (ff.object.object.class == TypeDeChampPrivate || type_champ == 'explication')
+    - hide_mandatory = (ff.object.object.private? || type_champ == 'explication')
     .form-group.mandatory{ style: hide_mandatory ? 'visibility: hidden;' : nil }
       %h4 Obligatoire ?
       .center
diff --git a/db/migrate/20180209133452_add_private_to_champ_and_type_de_champ.rb b/db/migrate/20180209133452_add_private_to_champ_and_type_de_champ.rb
new file mode 100644
index 000000000..5feb76084
--- /dev/null
+++ b/db/migrate/20180209133452_add_private_to_champ_and_type_de_champ.rb
@@ -0,0 +1,11 @@
+class AddPrivateToChampAndTypeDeChamp < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def change
+    add_column :champs, :private, :boolean, index: true
+    add_column :types_de_champ, :private, :boolean, index: true
+
+    add_index :champs, :private, algorithm: :concurrently
+    add_index :types_de_champ, :private, algorithm: :concurrently
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 320d92dc2..8db9e6a21 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2018_02_06_153121) do
+ActiveRecord::Schema.define(version: 2018_02_09_133452) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -138,7 +138,9 @@ ActiveRecord::Schema.define(version: 2018_02_06_153121) do
     t.string "type"
     t.datetime "created_at"
     t.datetime "updated_at"
+    t.boolean "private"
     t.index ["dossier_id"], name: "index_champs_on_dossier_id"
+    t.index ["private"], name: "index_champs_on_private"
     t.index ["type_de_champ_id"], name: "index_champs_on_type_de_champ_id"
   end
 
@@ -425,6 +427,8 @@ ActiveRecord::Schema.define(version: 2018_02_06_153121) do
     t.text "description"
     t.boolean "mandatory", default: false
     t.string "type"
+    t.boolean "private"
+    t.index ["private"], name: "index_types_de_champ_on_private"
   end
 
   create_table "types_de_piece_justificative", id: :serial, force: :cascade do |t|
diff --git a/spec/controllers/new_gestionnaire/dossiers_controller_spec.rb b/spec/controllers/new_gestionnaire/dossiers_controller_spec.rb
index 04d9586f2..5a08115b3 100644
--- a/spec/controllers/new_gestionnaire/dossiers_controller_spec.rb
+++ b/spec/controllers/new_gestionnaire/dossiers_controller_spec.rb
@@ -355,13 +355,11 @@ describe NewGestionnaire::DossiersController, type: :controller do
 
   describe "#update_annotations" do
     let(:champ_multiple_drop_down_list) do
-      type_de_champ = TypeDeChamp.create(type_champ: 'multiple_drop_down_list', libelle: 'libelle')
-      ChampPrivate.create(type_de_champ: type_de_champ)
+      create(:type_de_champ_private, type_champ: 'multiple_drop_down_list', libelle: 'libelle').champ.create
     end
 
     let(:champ_datetime) do
-      type_de_champ = TypeDeChamp.create(type_champ: 'datetime', libelle: 'libelle')
-      ChampPrivate.create(type_de_champ: type_de_champ)
+      create(:type_de_champ_private, type_champ: 'datetime', libelle: 'libelle').champ.create
     end
 
     let(:dossier) do
diff --git a/spec/models/champ_private_spec.rb b/spec/models/champ_private_spec.rb
index 733505696..5e3dee9af 100644
--- a/spec/models/champ_private_spec.rb
+++ b/spec/models/champ_private_spec.rb
@@ -1,7 +1,11 @@
 require 'spec_helper'
 
-describe ChampPrivate do
-  require 'models/champ_shared_example.rb'
+describe Champ do
+  describe '#private?' do
+    let(:type_de_champ) { build(:type_de_champ_private) }
+    let(:champ) { type_de_champ.champ.build }
 
-  it_should_behave_like "champ_spec"
+    it { expect(champ.private?).to be_truthy }
+    it { expect(champ.public?).to be_falsey }
+  end
 end
diff --git a/spec/models/champ_public_spec.rb b/spec/models/champ_public_spec.rb
deleted file mode 100644
index a981702c7..000000000
--- a/spec/models/champ_public_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require 'spec_helper'
-
-describe ChampPublic do
-  require 'models/champ_shared_example.rb'
-
-  it_should_behave_like "champ_spec"
-end
diff --git a/spec/models/champ_shared_example.rb b/spec/models/champ_shared_example.rb
index 60dc38e9a..6c42ed032 100644
--- a/spec/models/champ_shared_example.rb
+++ b/spec/models/champ_shared_example.rb
@@ -1,7 +1,7 @@
 shared_examples 'champ_spec' do
   describe 'mandatory_and_blank?' do
-    let(:type_de_champ) { TypeDeChamp.new(mandatory: mandatory) }
-    let(:champ) { Champ.new(type_de_champ: type_de_champ, value: value) }
+    let(:type_de_champ) { build(:type_de_champ_public, mandatory: mandatory) }
+    let(:champ) { type_de_champ.champ.build(value: value) }
     let(:value) { '' }
     let(:mandatory) { true }
 
@@ -34,7 +34,7 @@ shared_examples 'champ_spec' do
 
   context "when type_champ=date" do
     let(:type_de_champ) { create(:type_de_champ_public, type_champ: "date") }
-    let(:champ) { create(:champ, type_de_champ: type_de_champ) }
+    let(:champ) { type_de_champ.champ.create }
 
     it "should convert %d/%m/%Y format to ISO" do
       champ.value = "31/12/2017"
diff --git a/spec/models/champ_spec.rb b/spec/models/champ_spec.rb
index 6085a5719..f56a0f390 100644
--- a/spec/models/champ_spec.rb
+++ b/spec/models/champ_spec.rb
@@ -5,9 +5,17 @@ describe Champ do
 
   it_should_behave_like "champ_spec"
 
+  describe '#public?' do
+    let(:type_de_champ) { build(:type_de_champ_public) }
+    let(:champ) { type_de_champ.champ.build }
+
+    it { expect(champ.public?).to be_truthy }
+    it { expect(champ.private?).to be_falsey }
+  end
+
   describe '#format_datetime' do
-    let(:type_de_champ) { TypeDeChamp.new(type_champ: 'datetime') }
-    let(:champ) { Champ.new(type_de_champ: type_de_champ, value: value) }
+    let(:type_de_champ) { build(:type_de_champ_public, type_champ: 'datetime') }
+    let(:champ) { type_de_champ.champ.build(value: value) }
 
     before { champ.save }
 
@@ -25,8 +33,8 @@ describe Champ do
   end
 
   describe '#multiple_select_to_string' do
-    let(:type_de_champ) { TypeDeChamp.new(type_champ: 'multiple_drop_down_list') }
-    let(:champ) { Champ.new(type_de_champ: type_de_champ, value: value) }
+    let(:type_de_champ) { build(:type_de_champ_public, type_champ: 'multiple_drop_down_list') }
+    let(:champ) { type_de_champ.champ.build(value: value) }
 
     before { champ.save }
 
@@ -64,7 +72,7 @@ describe Champ do
 
   describe 'for_export' do
     let(:type_de_champ) { create(:type_de_champ_public, type_champ: type_champ) }
-    let(:champ) { Champ.new(type_de_champ: type_de_champ, value: value) }
+    let(:champ) { type_de_champ.champ.build(value: value) }
 
     before { champ.save }