Tips for installing windows in old Lithuanian project houses

Tips for installing windows in old Lithuanian project houses

Replacing or installing PVC windows in older panel buildings (typical Soviet-era panel house common in Lithuania) requires special care: irregular openings, settled reveals, higher humidity and specific wall structures. This guide provides practical steps from assessment and measurements to final finishing, plus common pitfalls and answers to FAQs.

1. Assess the opening

• Inspect the opening for cracks, damp stains, spalled concrete and rusted reinforcement.
• Check horizontals and verticals with a spirit level and measure depth in several places.
• Measure width, height and depth in three points (top, middle, bottom). Use the smallest measurement when ordering the frame.

For old project houses, actual dimensions often differ from drawings — trust real measurements.

2. Choose the right frame and glazing

• Prefer profile systems with good insulation and a mounting depth of at least 70–90 mm.
• Select insulated glass units with Low-E coating and argon fill for better thermal performance.
• For wide openings consider reinforced profiles and appropriate steel reinforcement.

3. Opening type and additional features

• For kitchens and bathrooms, ventilation sashes or micro-vent features are useful.
• Plan for external sills and recesses; ensure proper water drainage paths.
• Install sills and drip edges with an outward slope of 5–10°.

4. Removing the old frame and preparing the opening

• Remove the old frame carefully, clear out old sealant and foam.
• Clean the surfaces from dust and debris; treat any exposed metal with anti-corrosion primer.
• Check structural integrity; reinforce the opening if needed.

5. Step-by-step installation

1. Place the frame on temporary shims and check geometry.
2. Secure the frame with anchors or mounting plates, following recommended spacing.
3. Adjust sashes and align the frame before final fixing.
4. Fill the mounting gap with foam, then apply vapor and wind barrier tapes as a layered system.

6. Sealing and insulation scheme

• Use a layered approach: interior — vapor-tight tape, middle — PU foam, exterior — wind- and waterproof tape.
• High-quality gaskets and seals extend the lifespan and reduce drafts.

7. Water drainage and sills

• Ensure the external drip cap is installed with an offset from the facade and proper slope.
• Internal sill must be supported on leveling wedges with an allowance for thermal expansion.

8. Ventilation and moisture control

• Old solid-sealed windows can reduce natural airflow — install micro-ventilation or ventilation valves.
• Without ventilation, moisture and indoor air quality can worsen after replacement.

9. Common mistakes to avoid

• Incorrect measuring is the most common issue leading to poor fit.
• Sealing outside but not providing interior vapor barrier causes condensation and mold.
• Insufficient reinforcement on large openings causes frame deformation.

10. When to call professionals

• If the opening is heavily deformed, shows structural cracks or corroded reinforcement.
• For complex assemblies, integrated elements or relocation of sills and radiators.

FAQ — Practical answers

Q: Should the opening be reinforced before installation?

A: Yes, when cracks, spalling concrete or damaged reinforcement are present. Reinforcement methods include anchor frames, added masonry, or concrete patching depending on damage extent.

Q: What mounting gap width is recommended?

A: Typically 10–20 mm on each side is sufficient for foam and tapes. In uneven openings allow wider gaps and use shims to align the frame.

Q: How to prevent cold bridges under the sill?

A: Proper thermal insulation under the internal sill, combined with a well-fitted external drip and correct sealing, helps avoid thermal bridges.

Q: Should interior slopes be plastered or covered with plastic?

A: Plastering with reinforcing mesh and proper insulation is more durable and provides better finishing. Plastic panels are faster but may hide moisture problems.

Q: Can I install a window myself?

A: DIY installation is possible for simple, even openings if you have tools and experience. For irregular openings, significant repairs, or large frames hire professionals.

Note: These tips are tailored for typical Lithuanian panel houses. When in doubt, document the opening with photos and invite a professional to evaluate.

Final checklist before ordering

• Three-point measurements, photos of the opening, knowledge of nearby radiators and sills, and decision on ventilation options. Accurate documentation speeds up correct fabrication and reduces on-site adjustments.