2.2
石積みの空洞壁
空洞壁は、外側の枠と内側の枠の間に空洞があり、耐腐食性の金属タイでのみ接続されています。外側の枠から水が浸み出すと、この空洞内に下降し、フラッシュで遮断されて、最終的に排水穴から排出されます。耐湿性を高めるために、内側の枠の空洞側には防湿処理が施されることが多く、空気バリアとしても機能します。空洞に…
石積みの空洞壁は、中空のスペースで区切られた2つのワイスで構成されています。外側と内側のワイスは、構造安定性のために耐腐食性の石積みタイを使用して接続されています。
水が外側のワイスに浸透すると、キャビティに入り、キャビティの底に設置され、ウィープホールから排出されるフラッシングと呼ばれる薄い不浸透膜によって収集されます。
さらに、インナーワイスのキャビティ側に防湿材を塗布することで、内部を水の浸入から保護し、空気バリアとしても機能します。
建設中、モルタルの糞などの破片が排水システムを塞ぐ可能性があるため、空洞をきれいに保つことが重要です。モルタルのたわみ材料を使用すると、キャビティ内の排水の詰まりを防ぐことができます。
この空洞は、遮音性と建物内のユーティリティ分配用の導管の配置を容易にします。
また、キャビティに硬質発泡プラスチックの断熱板を挿入することで、断熱性を高めることができます。
キャビティ壁は、耐荷重性または非耐荷重性にすることができます。耐力キャビティ壁では、内側のワイスが構造荷重を支え、非構造的な外側のワイスがベニヤです。
非耐力壁では、内側のワイスが組積造の枕木を通じて外側のワイスに横方向の支持を提供します。
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Q1: What are the two main components of a masonry cavity wall?
A masonry cavity wall consists of two wythes—an outer wythe and an inner wythe—separated by a hollow space. These wythes are connected using corrosion-resistant masonry ties that provide structural stability. The cavity between them serves multiple functions, including moisture management, insulation placement, and utility distribution.
Q2: How does water drainage work in a cavity wall system?
When water penetrates the outer wythe, it enters the cavity and is collected by flashing, an impervious membrane installed at the cavity's bottom. The water then drains out through weep holes. Dampproofing material applied to the cavity side of the inner wythe prevents water from reaching interior spaces and also functions as an air barrier, protecting the building from moisture damage.
Q3: Why is keeping the cavity clean during construction important?
Debris like mortar droppings can block the drainage system, preventing water from exiting through weep holes and compromising the wall's moisture protection. Using mortar deflection material or beveled bed joints helps prevent mortar from entering the cavity. Traditional practices involved placing steel ties to catch droppings, which are then removed, but modern deflection methods are more effective and easier to implement.
Q4: What are the differences between load-bearing and non-load-bearing cavity walls?
In load-bearing cavity walls, the inner wythe supports structural loads while the outer wythe functions as a nonstructural veneer. In non-load-bearing cavity walls, the inner wythe provides only lateral support to the outer wythe through masonry ties, supporting only its own weight. Both configurations use corrosion-resistant ties to maintain structural connection between the wythes.
Q5: How can cavity walls provide thermal insulation?
Rigid foam plastic insulating boards can be inserted within the cavity space to provide thermal insulation and mitigate heat transfer through the wall assembly. This placement leverages the existing hollow space without requiring additional structural modifications, making it an efficient method for improving the building's energy performance while maintaining the cavity's drainage and moisture management functions.
Q6: What additional functions does the cavity space serve beyond moisture control?
Beyond moisture management, the cavity facilitates sound insulation, reducing noise transmission through the wall. It also provides space for placing conduits and utilities for building distribution systems. The hollow space allows for flexible routing of electrical, plumbing, and mechanical systems without compromising the structural integrity of the masonry wythes.
Q7: How do masonry ties contribute to cavity wall performance?
Corrosion-resistant masonry ties connect the outer and inner wythes, providing essential structural stability and lateral support. In non-load-bearing walls, ties support the outer wythe's weight and resist lateral forces. Their corrosion resistance ensures long-term durability and prevents deterioration that could compromise the wall's structural integrity and the connection between wythes.