Covering walls with penoplex: a step-by-step guide from preparation to finishing

Wall insulation penoplex - one of the most effective ways to reduce heat loss in a garage, workshop or residential premises. This material, which is extruded polystyrene foam, combines low thermal conductivity, moisture resistance and strength. However, even experienced car owners often have questions: how to fix the slabs correctly, do the walls need to be vapor-insulated, and what mistakes lead to condensation or mold?

In this article we will analyze the entire process - from choosing Penoplex (compare brands Comfort, Facade and GEO) until finishing. We will pay special attention to the nuances of installation in unheated rooms (garages, boxes), where changes in temperature and humidity place increased demands on thermal insulation. You'll find out why when covering metal garage walls with penoplex, a ventilation gap of 20–30 mm is required, and when insulating brick walls you can do without it.

1. Choosing penoplex: which brand is suitable for walls

Not all types penoplex equally effective on vertical surfaces. The manufacturer produces several lines of material that differ in density, compressive strength and purpose. Suitable for wall covering:

• 🔹 Penoplex Comfort - a universal option for internal insulation of residential premises and garages. Density 25–35 kg/m³, thermal conductivity coefficient 0.034 W/m·K. Suitable for walls under plaster or drywall.
• 🔹 Penoplex Facade — optimized for external insulation under plaster systems. Density 25–32 kg/m³, has a rough surface for better adhesion to glue.
• 🔹 Penoplex GEO — a budget line for insulating basements and basement walls. Density 28–33 kg/m³, but less resistant to mechanical loads.

It is better to choose for garages and workshops Penoplex Comfort or Facade 50–100 mm thick. If the walls are metal, the minimum thickness of the insulation should be not less than 80 mmto avoid the formation of “cold bridges”. When covering brick or concrete walls, 50 mm is sufficient.

⚠️ Warning: Do not use Penoplex 45 (for road construction) or Roofing (for pitched roofs) - these brands have excess strength, but worse thermal insulation properties for vertical surfaces.

Penoplex brand	Density, kg/m³	Thickness, mm	Purpose	Price per m² (2026)
Comfort	25–35	20–100	Interior walls, garages	350–700 ₽
Facade	25–32	30–120	External insulation under plaster	400–800 ₽
GEO	28–33	20–100	Basements, basements, budget insulation	300–650 ₽

When purchasing, pay attention to slab edges: in high-quality penoplex they have an L-shaped edge (step), which eliminates cold bridges when joining. If the edges are smooth, it may be a fake or low grade material.

2. Wall preparation: what needs to be done before installation

50% of the success of insulation depends on the quality of surface preparation. Neglecting this stage leads to peeling of the slabs, the appearance of fungus or freezing of the walls. The preparation algorithm differs depending on the base material:

• 🧱 Brick/concrete: Remove old plaster, paint or wallpaper. Seal the cracks with cement mortar and treat the surface deep penetration primer (for example, Ceresit CT 17).
• 🪜 tree: saturate the walls antiseptic (for example, Senezh Bio) and fire retardant. Cover the cracks with foam or tow.
• ⚙️ Metal: Clean off the rust with a brush or sandblast, cover primer for metal (for example, Hammerite). For garages, be sure to install sheathing with a ventilation gap!

General rule for all types of walls: the difference in plane should not exceed 1 cm per 1 m². If there are more unevenness, level the surface with plaster or putty. To check, use a 2 m long rule or a laser level.

Cleaning of old coating|Sealing cracks and potholes|Primer (2 layers with drying)|Checking levelness|Installation of vapor barrier (if necessary)-->

⚠️ Attention: If the walls of the garage or basement are damp, install forced ventilation or drill additional vents. Penoplex does not allow moisture to pass through, and without condensation drainage, water will accumulate underneath it.

For metal garages it is critical to comply ventilation gap 20–30 mm between the wall and the insulation. It is provided using lathing made of galvanized profiles or wooden blocks (treated with an antiseptic). Without a gap, condensation will form on the inside of the metal, which will lead to corrosion.

3. Tools and consumables: complete list

To cover walls with penoplex you will need:

Category	Tools/materials	Notes
Basic Tools	Foam saw, utility knife, drill mixer, notched trowel (10 mm), needle roller	To cut penoplex, it is better to use a hacksaw - a stationery knife crumbles the edges
Fasteners	Adhesive foam (Tytan Styro 750), dowel-umbrellas (8–10 pcs/m²), polyurethane foam, foil tape	Choose dowels with a plastic nail and a thermal head
Additionally	Primer, reinforcing mesh (140–160 g/m²), starting profile, corners with mesh	The mesh must be alkali-resistant (for example, OSNOVIT T-14)

Don’t skimp on glue: cheap foam can corrode penoplex. Optimal options - Tytan Styro 750, Makroflex 65 or Penoplex Facade. Consumption of adhesive foam is 1 can per 10–12 m². Use umbrella dowels only after the glue has completely dried (after 24–48 hours).

4. Step-by-step instructions: how to attach penoplex to the wall

The installation technology depends on the type of walls and finishing. We will look at a universal method suitable for garages, basements and living spaces.

Step 1: Marking and installing the starting profile

Mark the bottom border of the insulation on the wall using laser level or hydraulic level. Pin the starting profile (for example, Penoplex SP) around the perimeter of the room. It will keep the slabs from sliding and protect the bottom edge from rodents.

Step 2: Gluing the boards

Apply foam adhesive to penoplex along the perimeter and 2–3 stripes in the middle. Place the slab against the wall, starting from the corner, and press for 10–15 seconds. Join the slabs with a bond (like brickwork), avoiding cross joints. Fill gaps larger than 2 mm polyurethane foam without toluene (for example, Soudal).

How to cut penoplex without crumbs?

Use a fine-tooth hacksaw or nichrome wire heated to 120–150°C. For curved cuts, a jigsaw with a foam file is suitable.

Step 3: Additional dowel fastening

24 hours after gluing, secure the slabs with umbrella dowels. Place them in the corners and in the center of each slab (5-6 pieces per m²). For metal walls, use dowels with an enlarged head (Hilti X-DUO). Before drilling, check for hidden wiring!

Step 4: Sealing the joints

Foam all seams more than 1 mm wide, cut off the excess after drying. To seal joints between slabs you can use foil tape or butyl rubber tape.

5. Finishing insulated walls: options for garage and home

Without finishing, penoplex will quickly lose its properties under the influence of UV rays and mechanical damage. The choice of material depends on the purpose of the room:

• 🏠 Residential premises:

  ✅ Plaster over reinforcing mesh (wet facade system)

  ✅ Drywall on sheathing (with 20 mm ventilation gap)

  ✅ Decorative panels (PVC, MDF)

• 🚗 Garages/workshops:

  ✅ Corrugated sheeting on the sheathing (the most durable option)

  ✅ OSB boards followed by painting

  ✅ Plaster with added fiber fiber for strength

For plastering, use cement-based mixtures (for example, Ceresit CT 24>) with reinforcing mesh. Apply layers no thicker than 3-4mm at a time to avoid cracking. In garages it is better to give preference corrugated sheets — it is shock-resistant, non-flammable and easy to clean.

If you plan to paint penoplex, choose acrylic or silicone paint with a vapor permeability of at least 130 g/m²·day. Solvent based paints (e.g. PF-115) corrode the material!

6. Common mistakes and how to avoid them

Even experienced craftsmen make mistakes when working with penoplex. Here are the most critical of them:

• 🔥 Ignoring the ventilation gap for metal walls. Result: metal corrosion due to condensation. Solution: install a sheathing made of 20x40 mm timber.
• 💧 No vapor barrier in rooms with high humidity. Result: wetting of the insulation and loss of thermal insulation properties. Solution: use vapor barrier membrane (for example, Izospan B).
• 🧱 Fastening slabs to polyurethane foam instead of foam glue. Result: peeling of the insulation after 1–2 years. Solution: Use only specialized glue for expanded polystyrene.
• ⚡ Laying wiring under penoplex without corrugation. Result: risk of fire. Solution: lay all cables in metal hose or corrugated pipe.

⚠️ Attention: When insulating a garage, never use polystyrene foam instead of penoplex! Penoplast absorbs gasoline, oils and solvents, and in the event of a fire it emits toxic smoke. Penoplex is safer in this regard - it is self-extinguishing (flammability group G1).

Another common mistake is incorrect joining of plates. If the seams between the slabs form a cross, there will be cold bridges in these places. Always offset the joints in adjacent rows by half the width of the slab (staggering technique).

7. Cost of cladding: calculation for a 6×4 m garage

We will calculate the estimated cost of insulating a standard garage with penoplex Comfort 50 mm thick (wall area ~40 m², excluding gates):

Material/work	Quantity	Cost, ₽
Penoplex Comfort (50 mm, 0.75 m²)	54 sheets	12 000
Adhesive foam Tytan Styro 750 (750 ml)	5 cylinders	3 500
Dowel umbrellas (8 pcs/m²)	320 pcs.	1 600
Reinforcing mesh (140 g/m²)	45 m²	2 700
Corrugated sheeting for finishing	40 m²	8 000
Total (materials)	27 800
Work (when hiring a team)	40 m²	15 000–20 000

You can save money by doing the work yourself. The main expense items are insulation (40–50% of the budget) and finishing. If you use corrugated board instead OSB boards, the cost will decrease by 30–40%.

💡

Buy penoplex and consumables in large construction hypermarkets (for example, Leroy Merlin or Castorama) - there are often “3+1” promotions or discounts of up to 15% when ordering over 50 sheets.

Frequently Asked Questions

Is it necessary to insulate the walls of the garage with penoplex if it is heated with a potbelly stove?

Yes, especially if the garage is metal. Without insulation, the heat from the stove will escape through the walls within 1–2 hours after warming up. Penoplex with a thickness of 50–80 mm will reduce heat loss by 60–70%, and 2–3 times less fuel will be required. The main thing is to ensure a ventilation gap and fire-safe installation (the distance from the potbelly stove to the walls with penoplex foam should be at least 50 cm).

Is it possible to glue penoplex to polyurethane foam?

No, polyurethane foam is not suitable for permanently gluing slabs. It has low adhesion to penoplex and peels off over time. Use only glue foam on a polyurethane basis (for example, Tytan Styro 750 or Penoplex Facade). Polyurethane foam can only be used to seal joints more than 2 mm wide.

Which side to attach the penoplex: smooth or rough?

Both sides of penoplex have the same thermal insulation properties. However, if one side has a rough surface (like Penoplex Facade), it is recommended to turn it against the wall - this improves adhesion to the glue. The smooth side should “look” outward (toward the room).

What to do if condensation appears on the walls after insulation?

Condensation occurs due to impaired vapor permeability or lack of ventilation. Solutions:

• 🔹 Install supply valve or exhaust fan.
• 🔹 Check the tightness of the joints - seal the cracks.
• 🔹 If you insulated a metal garage, increase the ventilation gap to 40–50 mm.
• 🔹 In residential areas, add vapor barrier membrane from the side of warm air.

How long will penoplex insulation last in a garage?

With proper installation and finishing, penoplex retains its properties 30–50 years. Main factors of durability:

• 🔹 Protection from UV rays (finishing with plaster, corrugated board or paint is required).
• 🔹 No mechanical damage (in garages it is better to use corrugated sheets instead of drywall).
• 🔹 Tightness of joints (check and glue seams every 2-3 years).

In an aggressive environment (constant humidity, chemical fumes), the service life is reduced to 15–20 years.