Exterior concrete surfaces
GeneralConcrete is used in outdoor building structures such as facades, load-bearing walls, plinths, and balconies.
Concrete facades are usually constructed from Sandwich elements that contain insulation between the interior and exterior shells. Exterior shell thickness can vary between 50 and 70 mm. Facade element seams are sealed with elastic joint compound, which protects the element base from moisture and allows for thermal expansion in the elements.
The element surface may be painted, unpainted, faced with natural stone or exposed-aggregate concrete, or tiled. For example, brick-faced elements have approx. 15 mm-thick shells moulded into the element, whereas various clinker and other tiles are only embedded to a few millimetres’ depth.
Load-bearing walls are freestanding concrete structures cast on site or in specially designed elements. A common wall type is the cellar ramp supporting wall that is backed by higher level ground, i.e. earth mass is held back by the wall.
In Finland, concrete plinths are always used as building foundations, and are made from elements or cast on site.
Since the early 1970s, balconies in Finland have usually been constructed from elements. In other words, concrete floor, ceilings and wall frame elements are pre-installed at the factory.
Common fault mechanisms in facade element structural unitsFaults occurring in concrete
The rusting of steel reinforcements in concrete elements can cause damage. When corroded, the volume of steel expands and causes the concrete to crack. Water penetrating into the structure from cracks then produces unsightly rusty water stains on the concrete surface. This is followed by fissures that, when enlarged, accelerate corrosion and frost weathering. Finally, pieces of concrete start to break off and even expose the rusting steel.
Damaged element seams that have lost their elasticity increase the risk of frost damage to the elements, which can then cause damage to nearby paint surfaces. Element base insulation may also be exposed to moisture.
Load-bearing walls and plinths
The most common problems with load-bearing walls are due to the poor condition of waterproofing on their interior surfaces. Proper waterproofing is the key to successfully painting walls, but it may be damaged or missing completely. Damp rising into plinths through capillary action often causes efflorescence (salt deposits) and paint peeling.
Typical trouble spots include the upper inner corners of dividing jamb walls. Moisture often seeps into the structures from the outside, especially if the horizontal element seam is made of plaster. Plaster seams absorb the rainwater running down the jamb, which causes paint to peel. Insufficient water proofing of upper balcony floors can also cause damage to paint on ceilings and upper walls of lower balconies.
Paint surface condition
Check the state of painted surfaces visually once a year, and carry out the first detailed evaluation ten years after painting. Tikkurila technical advice services can also help with the evaluation process, and building specifications and maintenance logs may also be useful when available. Compare the documentation to present conditions to reveal any discrepancies in the paperwork.
Pay attention to the structural condition of concrete facades, i.e.:
- the state of concrete structures, i.e. cracks and fissures
- element seams
- the condition of related structures, e.g. roofs, gutters, and down pipes.
Washing and maintenance instructionsWhen maintaining exterior concrete surfaces, the person responsible for property maintenance should plan the work systematically by first ordering an evaluation report. Do it yourself maintenance may hinder systematic maintenance in the future. For example, using the wrong type of paint might require special pre-treatment that would otherwise have been unnecessary.
Gentle pressure washing without detergent is usually sufficient for cleaning or washing the surfaces.
Remove biological growth such as fungus and mould with hypochlorite solution and then rinsing thoroughly.
When selecting maintenance paint, apply the same type of paint as used previously to the facade.
For further instructions, refer to Masonry facades and product data sheets.