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Do Balconies Need To Be Waterproofed?

Yes, balconies need to be waterproofed. Not waterproofing a balcony would lead to a number of problems. If a balcony was screeded and left without waterproofing, over time rainfall would be absorbed by the screed. As soon as the house is heated, the water will be drawn through the substate causing enormous damage. this can be to the ceiling if there is one below or on the exposed bottom of the balcony if there is not.

A balcony with a concrete substrate which has suffered the absorption of rainwater into the screed will result in the water reacting with the chemicals in the concrete. The reaction hardens the water and results in stalactites 1. These stalagmites will hang from the bottom of an exposed balcony. Obviously both these situations are dangerous and hanging stalactites can be a danger to anyone walking beneath.

How Do You Waterproof An Outside Balcony

You can waterproof an outside balcony balcony using mastic asphalt or a liquid waterproofing system. A balcony waterproofed with mastic asphalt is commonly referred to as an asphalt balcony. Sheathing felt is laid on top of cementious screed 2 laid to falls to allow for movement between the screed and the asphalt membrane. The asphalt is laid in two coats of roofing grade asphalt to a nominal thickness of 20mm. This asphalt will be joint to an asphalt upstand with an angle fillet to completely waterproof the substrate of the balcony. This upstand must be 150mm high and must go into a chase cut into the wall. Once the two coats of mastic asphalt and the upstand have been laid a further coat of mastic asphalt  will be laid this time with paving grade asphalt to a nominal thickness of 25mm. This paving grade asphalt has extra grit added to it to provide extra hardness.

If paving is to be added, the next steps will depend upon the bedding used. If it is a mortar bedding, building paper or a sheet of felt will have to be laid on top of the mastic asphalt before the mortar is laid. If the bedding is sand this is not necessary. Flexible non-bio degradable board will be laid around the perimeter to allow for movement. Once this board is down the sand or mortar bedding can be applied. The sand bedding must be 50mm in nominal thickness. Once either the sand or mortar bedding is laid paving can be applied on top to complete the balcony.

Need More Information About Waterproofing A Balcony?

If you would like a quotation or any information about the waterproofing of a balcony please get in touch with us or call us now on 01277 375 511. One of our friendly team of waterproofing specialists will be happy to help