A home that is cold in winter and hot in summer; recurring mould on walls; water seeping to the neighbour below — these problems share one name: missing insulation. Thermal insulation targets energy loss; waterproofing targets damp and leaks. They solve different problems, but when they are not planned together, one undermines the other.
What is external wall insulation and how is it applied?
External insulation means covering a building’s outer walls with insulation boards and applying render, mesh and a top coat over them. The layers, in order:
- Surface preparation and starter profile
- Insulation board (adhesive plus mechanical fixings)
- Render and mesh (reinforcement layer)
- Primer
- Top coat: mineral plaster or exterior paint
Window reveals, sills and movement joints must be detailed to keep water out; most insulation failures start at these points.
Which insulation material goes where?
| Material | Key property | Typical use |
|---|---|---|
| EPS | Economical, light | External wall insulation |
| XPS | Moisture resistant, high compressive strength | Plinth, foundation, flat roof |
| Mineral wool | Non-combustible, good acoustics | High-rise facades, boiler rooms |
| Glass wool | Economical, good acoustics | Loft spaces, partition cavities |
| Polyurethane | High insulation value | Roofs, sandwich panels |
Mineral wool is used where fire safety is required on tall buildings; XPS is used on surfaces in contact with the ground.
Where is waterproofing needed?
Foundation tanking: wrapping foundations and basement walls in contact with soil from the outside. It is done during structural works; doing it later requires excavation.
Roof: membrane on flat roofs, a watertight layer beneath the covering on pitched roofs.
Wet areas: liquid-applied waterproofing beneath tiles on bathroom and kitchen floors, with taping at wall bases. It is a standard step during plumbing renewal.
Balconies and terraces: falls, waterproofing and drain details must be resolved together.
How are mould and damp related to insulation?
The inner face of an uninsulated external wall stays cold in winter; humid indoor air condenses on that surface and mould forms. Insulation raises the wall’s surface temperature and reduces condensation. But if the source of the mould is a leak or a plumbing fault, that must be fixed first — see our article on damp and mould on walls.
What to watch for during insulation work
- Board thickness should suit the local climate and the building’s condition
- Fixing quantity and adhesive application must follow the standard
- Window and balcony details must prevent water ingress
- Do not apply in freezing or extremely hot conditions
- In apartment buildings, the owners’ decision and budget plan must be agreed in advance
It is worth reading this alongside our guide to facade cladding options.
What determines the cost?
Facade area, insulation material and thickness, top coat choice, scaffolding duration and building height determine external insulation cost; the number of points and material type determine waterproofing cost.
Demgirişim delivers thermal and waterproof insulation — facade, roof, foundation and wet areas — with a single team.
Frequently asked questions
Does external insulation really save money?
A significant share of heat loss happens through external walls; insulation reduces that loss and lowers heating and cooling bills. The saving depends on the building's current state, insulation thickness and climate.
Can insulation be applied from the inside?
Internal insulation is possible but less effective than external and carries a condensation risk. It can be considered when a whole-building facade decision cannot be reached.
What is wet area waterproofing?
A watertight layer applied to bathroom and kitchen floors and wall bases beneath the tiling. It is standard practice during plumbing renewal to prevent leaks to the flat below and damp in walls.
The initial consultation and written quote for Thermal & Waterproofing are free within Istanbul. Scope, duration and cost are confirmed after the consultation.