How to Insulate a Floor

A Step-by-Step Guide to Installing Floor Insulation

Insulating your floor can significantly improve energy efficiency and comfort in your home. Follow this step-by-step guide to properly install floor insulation based on your floor type.

Step 1: Identify Your Floor Type

Before starting, determine whether you have a suspended timber floor, solid concrete floor, floating floor, or screed finish floor, as the installation process varies for each.

• Suspended Timber Floors are common in older properties and have a gap or void beneath the floor, allowing for ventilation. Insulating these floors requires lifting the floorboards and inserting insulation material between the joists, such as mineral wool or rigid foam boards. 
• Solid Concrete Floors are found in more modern homes or basements, concrete floors require insulation that can be installed directly above the concrete surface. This can be done using rigid foam boards or polystyrene boards, which are then covered by a new floor covering.
• Floating floors are often used in modern buildings and involve a layer of insulation placed on top of the existing floor surface. The floor covering (such as laminate or engineered wood) is then installed over this insulation, with the floor 'floating' rather than being fixed to the subfloor. For insulation, you can use underlay materials or foam boards, which help reduce heat loss and sound transmission.
• Screed Finish Floors or a screed finish refers to a thin layer of cement or concrete placed over an existing floor or insulation. It is typically used to smooth out surfaces or provide a finished floor for tiles or other coverings. To insulate screed floors, you typically lay insulation boards (like polystyrene or foam) under the screed layer to ensure thermal efficiency.

Step 2: Gather The Necessary Materials and Tools

Having the right materials and tools will make the insulation process smoother and more efficient. Make sure you have the following:

1. Insulation material (mineral wool, rigid foam boards, polystyrene, or Kingspan)

• Mineral Wool is Ideal for timber floors, mineral wool is flexible and can easily be cut to fit between joists. It also provides soundproofing benefits. See Recommended products:

• Rigid Foam (PIR) Boards include polystyrene, polyisocyanurate, and polyurethane boards. They offer excellent thermal performance and are ideal for concrete or suspended floors. See Recommended products: 

• Polystyrene is widely used for concrete floors, polystyrene is affordable and offers effective thermal insulation.

• Kingspan Insulation is a high-performance brand known for its thin, effective insulation boards, Kingspan offers great thermal insulation with a slim profile, perfect for floors where space is limited.

2. Tape measure to ensure accurate cuts

3. Utility knife or saw for cutting insulation to size

4. Protective gloves and mask

5. Wooden battens (for suspended floors) to hold insulation in place

6. Adhesive for securing insulation (if required)

7. Screed mix (if required for screed floors)

8. Floor covering materials (e.g., laminate, engineered wood, tiles)

Step 3: Install the Insulation

For Suspended Timber Floors:

• Lift the Floorboards: Carefully remove the floorboards using a crowbar or screwdriver, taking care not to damage them.
• Install Support Battens (if necessary): If insulation needs additional support, fix wooden battens between the joists to hold it securely in place.
• Cut and Place Insulation: Measure and cut mineral wool or rigid foam boards to fit snugly between the joists, ensuring full coverage.
• Secure the Insulation: Staple breathable netting or a membrane over the insulation to keep it in position while allowing airflow.

Video credited to Credit to Ali Dymock. Check out his channel: https://www.youtube.com/@AliDymock

For Solid Concrete Floors:

• Clean and Prepare the Surface: Sweep and clean the concrete floor to remove debris and ensure a smooth surface.
• Lay a Damp-Proof Membrane: This is essential to prevent moisture from seeping into the insulation, protecting it from dampness.
• Install Rigid Foam or Polystyrene Boards: Position the insulation boards evenly over the membrane, covering the entire floor surface.
• Apply Floor Covering: Depending on your preference, lay plywood, underlay, or install new flooring materials such as laminate, carpet, or tiles over the insulation.

For Floating Floors:

• Prepare the Existing Floor: Ensure the floor is clean, level, and free from obstructions.
• Lay Insulation Underlay or Foam Boards: Spread the insulation evenly across the entire floor surface to create a thermal barrier.
• Install the Floating Floor Covering: Position laminate, engineered wood, or other floating flooring materials on top of the insulation without fixing them to the subfloor, allowing for natural expansion and movement.

For Screed Finish Floors:

• Lay Insulation Boards: Arrange polystyrene or rigid foam boards evenly on the subfloor, ensuring full coverage.
• Apply a Screed Layer: Pour and smooth a thin layer of screed mix over the insulation.
• Smooth and Let It Cure: Allow the screed to dry completely before installing any final floor covering such as tiles or laminate.

Step 4: Finishing Touches

For Suspended Timber Floors:

• Seal Gaps: Use sealant around edges and gaps to prevent drafts and heat loss.
• Check for Moisture Issues: Ensure proper ventilation to avoid damp problems.
• Install Skirting Boards or Floor Trims: Fit skirting boards or trims along the edges to create a polished and seamless look.

For Solid Concrete Floors:

• Seal Gaps: Use a sealant to secure the edges and improve insulation effectiveness.
• Ensure a Level Surface: Double-check that the insulation is even before laying floor coverings.

For Floating Floors:

• Trim Excess Insulation: Ensure a neat fit before placing the final floor covering.
• Use an Expansion Gap: Leave a small gap around the perimeter to allow for floor expansion and prevent warping.

For Screed Finish Floors:

• Check for Leveling: Ensure the screed layer is even before placing final floor materials.

Allow Full Curing Time: Wait for the recommended curing period before using the floor.ff

By following these detailed steps for each floor type, you can effectively insulate your floors, enhancing thermal efficiency and reducing energy bills. If your unsure, consult a installation professional for complex installations like screed floors or underfloor heating systems.