Invisiweep Wall Weeps

About Invisiweep Wall Weeps

Invisiweep wall weeps are almost invisible cavity drain units used to safely discharge water from external masonry walls. Designed for use in perpendicular joints, they provide an effective drainage channel wherever water may collect within a cavity wall.

They’re suitable for a wide range of applications, including use with cavity tray systems, over external lintels and at ground floor slab level. The discreet outlet design helps minimise visual impact on the finished brickwork while maintaining reliable drainage performance.

Invisiweep units are injection moulded from polypropylene and manufactured to recognised British Standards, making them suitable for use on both new build and refurbishment projects.

Where Invisiweep Wall Weeps Are Used

Invisiweep wall weeps should be installed anywhere water needs to be discharged from an external cavity wall, including:

• At ground floor slab level
• Within cavity tray systems
• Over external lintels
• On external masonry walls

Cavity wall weeps are required at regular intervals to allow moisture to escape from the cavity. They must be provided below DPC level and as part of any cavity tray run, including continuous cavity trays and gas protection barrier systems.

Why Use Invisiweep Instead of Open Perp Joints?

Leaving perpendicular joints open is still common on some sites, but this approach is unreliable. Open joints can become blocked with mortar, allow wind-driven rain into the cavity, and create access points for insects and small animals.

Invisiweep provides a proprietary alternative, designed and flow-tested to optimise water discharge while maintaining a small, concealed outlet size. This helps improve long-term performance and reduces the risk of blockages or ingress.

Key Design Features

Invisiweep wall weeps incorporate several features designed to improve drainage and reliability:

• Venturi effect outlet tube to reduce water pressure and encourage controlled drainage
• Discrete external outlet to minimise visual impact on brickwork
• Integral 4mm vermin barrier and rainwater baffle, as recommended by BS5250
• External ribs and tapered profile to key securely into mortar
• Full-height upstand on the cavity side to help maintain drainage and reduce blockage from mortar droppings

An extension tube (IW500EX) is available for wide walls and render finishes and can be cut to size on site.

Standards & Compliance

Invisiweep wall weeps are:

• Manufactured to BS EN ISO 9001 and BS EN ISO 14001
• Compliant with BS5250, BS8000, BS5628 and BS8215
• Fully compliant with relevant Building Regulations
• Suitable for use on NHBC-approved projects

Available Colours

Invisiweep wall weeps are available in a range of colours to suit surrounding brickwork:

• Clear
• Terracotta
• Buff
• Brown
• Grey
• Black
• Blue/Black
• White

The Invisiweep extension tube is available in Clear only.

Installation Guidance

For effective drainage, Invisiweep units should be installed directly on top of the base of a cavity tray, DPC or on the front edge of a lintel.

Key installation points:

• Install in perpendicular joints
• Place at 450mm centres above openings (minimum of two per opening)
• For perimeter cavity trays, centres may be increased to 900mm where appropriate
• Ensure the cavity side of the weep is kept clear of mortar during installation

For wide walls or rendered finishes, the extension tube can be inserted into the Invisiweep and trimmed to the required length.

Quantity Guide

To calculate quantities:

• Divide the total length of the cavity tray, DPC or lintel by 450mm and round up
• Allow a minimum of two Invisiweeps per opening
• Allow one Invisiweep per cavity tray stop end

Each Invisiweep is 102mm long and covers a standard external wall. Longer runs can be achieved using the extension tube where required.

FAQs – Invisiweep Wall Weeps

What is an Invisiweep wall weep used for?
It’s used to discharge water from cavity walls while keeping the external appearance of brickwork neat and unobtrusive.

Where should Invisiweep units be installed?
They should be installed over lintels, above cavity trays, at ground floor slab level and anywhere water may collect within a cavity wall.

Are open perp joints acceptable instead of weeps?
Open joints are prone to blockage and ingress. A proprietary unit like Invisiweep offers a more reliable and compliant solution.

Can Invisiweep be used with render finishes?
Yes. The extension tube allows Invisiweep to be used with wide walls and render and can be cut to size on site.