Concrete Spalling Behind Siding

Hydrostatic pressure is not the only cause of spalling.

Concrete spalling behind siding.

While spalling can occur on concrete it s especially a concern on stone brick or block where portions of the assembly can degrade to a point where they crumble. James hardie recommends that a slip sheet joint flashing is installed behind each butt joint in the siding. As weather changes the concrete expands causing it to spall which leads to further deterioration. Spalling is break away of concrete surface which often extends to the top layers of reinforcing steel.

The wood that goes under residential siding exterior sheathing performs several functions. Before that dries mix three parts fine sand and one part portland cement in your wheelbarrow with enough water to make the mix the consistency of thick oatmeal. It adds insulation waterproofing and structural support for the framing. Spalls can appear because the rebar has been exposed and humidity and water have begun to rust the rebar or because the concrete joints were improperly built.

Mix one part type 1 portland cement and one part fine sand by volume. Spalling that occurs in a concrete driveway or sidewalk typically happens because the weather changed during the hardening process or something else occurred to prevent the concrete from finishing its curing. Spalling of concrete affects a broad variety of structures including framed buildings multi storey car parks bridges jetties tanks and bunds. Contractors might make the mistake of adding too much water but frankly most don t make mixing errors.

Contrary to popular belief concrete is porous. Spalls may be 150 mm or more in diameter and 25mm or more in depth and the occurrence of smaller spalls also possible as per aci 302 1r 4. This is a 6 wide piece of weather resistive material to make sure that no water gets through. Most contractors will remember to do this but some of them try to save a buck by cutting squares of building paper for.

Concrete spalling typically begins when the steel reinforcing embedded within the concrete member rusts. Rusting of the embedded steel reinforcing occurs when that reinforcing bar is exposed to water and air. It also provides a. Spalling also can be caused by freeze thaw cycles in concrete and masonry products that have a high moisture content.

Over the course of a winter or over the course of years as the internal pressure rises and falls it stresses the surface layer of the concrete which leads to spalling. Without both of these elements the steel bar does not rust.