Which Type of Through-Wall Screw Should Be Selected for Basement Exterior Walls,Water Tank Walls,and Ordinary Shear Walls Respectively?

Which Type of Through-Wall Screw Should Be Selected for Basement Exterior Walls,Water Tank Walls,and Ordinary Shear Walls Respectively?

When selecting through-wall screws for basement exterior walls,water tank walls,and ordinary shear walls,the core basis lies in the wall’s waterproof requirements,stress conditions,and application scenarios.Due to their different functional orientations,the three types of walls have significant differences in their requirements for the water-stopping performance and strength of the screws.The specific selection is as follows:

1.Basement Exterior Walls:Prioritize"Water-Stop Through-Wall Screws"(with Water-Stop Plates/Rings)

Basement exterior walls are in direct contact with soil or groundwater,bear long-term external soil and water pressure,and need to strictly prevent groundwater and rainwater from seeping into the interior.Waterproofing is the core requirement,so screws with water-stopping functions must be used.Common types include:

(1)Embedded Water-Stop Through-Wall Screws(One-Piece/Three-Piece)

Structural Features:A circular water-stop plate(usually a 3–5mm thick steel plate with a diameter 50–80mm larger than the screw)is welded in the middle of the screw.Some three-piece water-stop screws also allow the two end sections of the screw to be removed after pouring(only the middle water-stop section remains combined with the wall),reducing the workload of later hole sealing.

Reasons for Adaptation:The water-stop plate can bond tightly with concrete to form a horizontal physical barrier,completely blocking the seepage path of water along the gap between the screw and concrete.The three-piece design also avoids the long holes left after the removal of traditional one-piece screws,reducing the risk of leakage from hole sealing.

Precautions:The water-stop plate must be welded firmly(no cold welding or cracks).The screw material should be Q235B or higher to ensure that the tensile and shear strength meet the requirements of soil and water pressure.

2.Water Tank Walls(Including Fire Water Tanks,Storage Tanks,Etc.):Select"Reinforced Water-Stop Through-Wall Screws"(High Water-Stop Grade+Anti-Corrosion Treatment)

Water tank walls are"water-facing structures"in long-term contact with water.They not only need to prevent water from seeping outward(e.g.,to the walls and soil outside the tank)but also resist the lateral thrust of water pressure inside the tank on the walls.At the same time,the screws need to withstand long-term water immersion(to avoid structural failure due to rust).The selection must meet the requirements of"high water-stopping performance+high corrosion resistance+high strength":

(1)Through-Wall Screws with Double Water-Stop Plates/Rings

Structural Features:1–2 additional water-stop plates(or spiral water-stop rings)are added in the middle of the screw to increase the water-stopping area;the surface of some screws is treated with anti-corrosion measures(such as hot-dip galvanizing,anti-corrosion coating),or stainless steel materials(e.g.,304 stainless steel,suitable for drinking water tanks)are used.

Reasons for Adaptation:Double water-stop plates can further improve the anti-seepage grade,avoiding leakage caused by welding defects of a single water-stop plate.Anti-corrosion treatment can prevent the screw from rusting due to long-term water immersion,avoiding concrete damage caused by rust expansion and indirectly reducing leakage risks.

Precautions:For drinking water tanks,anti-corrosion materials that meet food-grade standards(e.g.,304 stainless steel)must be used to prevent the precipitation of chemical substances.The screw spacing should be calculated based on the water pressure inside the tank to ensure the stability of the wall formwork support.

3.Ordinary Shear Walls(E.g.,Load-Bearing Shear Walls in Above-Ground Buildings):Select"Ordinary Through-Wall Screws"(No Water-Stop Function Required)

Ordinary shear walls mainly function to bear the vertical load of the building and horizontal seismic force.They have no waterproof requirements(most are located above ground and not in direct contact with water)and only need to meet the stress strength of formwork support.Therefore,no water-stopping structure is required,and ordinary smooth/threaded through-wall screws can be used.Common types include:

(1)Ordinary One-Piece Through-Wall Screws

Structural Features:No water-stop plate,mostly made of Q235 steel,with ordinary threads on the surface(facilitating cooperation with nuts to fix the formwork),and the length is customized according to the wall thickness.

Reasons for Adaptation:No need to consider waterproofing,simplifying the structure while reducing costs.The screw strength should be calculated based on the pouring height of the shear wall and the lateral pressure of concrete to ensure that the formwork does not expand or shift.

Precautions:After the concrete is poured and reaches the required strength,the screws need to be removed.Small holes will remain on the wall surface,which can be sealed with cement mortar later(since there are no waterproof requirements,simple sealing can meet the needs of appearance and structural integrity).