Platinum Cob Plugs

Q) What are Platinum Cob Plugs and what are they designed for?

A) Platinum Cob Plugs are specialist expanding-stem fixing plugs designed for securing damp proofing membranes and lining boards to weak, friable, undulating or low-density substrates in situations where standard fixing plugs may not achieve reliable grip. Used within the Platinum Damp Proofing System, they are well suited to above-ground installations with meshed and non-meshed membranes, including Platinum DM2, Platinum DM3 and Platinum PM3. Available in 60mm and 90mm lengths, the plug expands when the supplied central pin is driven into place, helping create a secure fixing in poor-quality base materials such as cob, soft historic brickwork, deteriorated blockwork and friable stone. For membrane installation, a fixing density of approximately 16 plugs per m² is recommended.

Q) What makes Platinum Cob Plugs different from standard damp proof membrane fixing plugs?

A) Platinum Cob Plugs differ from standard damp proof membrane fixing plugs through their expanding-stem mechanism. Standard fixing plugs rely on friction between the plug body and the surrounding masonry to create anchorage. In weak, soft or friable substrates, this friction is often insufficient and the plug can loosen or pull out during or after membrane installation. Platinum Cob Plugs address this directly by incorporating a supplied central pin that is driven into the plug body after insertion, physically expanding the stem inside the drilled hole. This mechanical expansion creates a much stronger grip in poor-quality base material, making the plugs reliable in situations where conventional membrane fixings consistently fail, particularly on cob walls, soft historic brickwork and deteriorated masonry.

Q) Where can Platinum Cob Plugs be used in damp proofing work?

A) Platinum Cob Plugs are designed for above-ground damp proofing applications where the wall substrate is too weak, soft or friable for standard fixing plugs. Typical uses include securing damp proof membranes to cob wall construction, older brickwork affected by age and moisture, friable stone substrates, deteriorated blockwork, and other poor-quality masonry backgrounds. They are suitable for Platinum DM2 and DM3 meshed membranes, Platinum PM3 non-meshed membrane, and compatible systems including Newton Newtonite, Newtonite Lath, Platon PB2 Mesh and Wykamol CM3 Mesh membranes. They can also be used for lining board fixing to difficult substrates. In higher risk damp situations, Newtonite 801 Mastic can be applied at the plug head before installation for additional moisture protection.

Q) When should Platinum Cob Plugs be chosen over standard Platinum Mesh Fix Plugs?

A) Platinum Cob Plugs should be chosen over standard Platinum Mesh Fix Plugs whenever the wall substrate is too weak, friable or undulating to provide reliable anchorage for a conventional straight fixing plug. Standard mesh membrane plugs are suitable for reasonably sound masonry such as standard modern brick, dense blockwork and concrete where a straight plug achieves adequate grip. Platinum Cob Plugs are the correct choice where the masonry is soft, deteriorated or irregular, including cob construction, soft historic brick, friable stone and poorly bonded blockwork. If there is any doubt about whether the substrate will hold a standard fixing, the expanding-stem action of the Cob Plug provides a more dependable mechanical solution for holding the damp proof membrane securely against the wall.

Q) What are the main advantages of Platinum Cob Plugs?

A) Platinum Cob Plugs offer a strong combination of practical advantages for damp proofing work on difficult substrates. The expanding-stem design provides stronger anchorage in weak, friable and low-density materials where standard fixings consistently fail. The availability of both 60mm and 90mm lengths allows installers to choose the most appropriate depth for the substrate condition and application. They are compatible with Platinum DM2, DM3 and PM3 membranes as well as compatible Newton, Platon and Wykamol damp proof membrane systems, providing flexibility across different project specifications. Newtonite 801 Mastic can be applied inside the fixing head for additional damp protection in higher risk areas. At the recommended density of 16 plugs per m², they provide a close and reliable fixing pattern for membranes on uneven or irregular wall surfaces.

Q) What technical specifications do Platinum Cob Plugs have?

A) Platinum Cob Plugs are available in two lengths, 60mm and 90mm, and have a 10mm width with an expanding stem design. Installation requires a 10mm SDS drill bit. For the 60mm plug, the hole should be drilled to a depth of approximately 65mm, and for the 90mm plug, approximately 95mm, allowing sufficient room for correct insertion and expansion. Each plug is supplied with a central nail or pin that is driven into the plug after insertion, causing the stem to expand and grip the surrounding substrate. The recommended fixing density for membrane installation is approximately 16 plugs per m². They are suitable for use with both meshed and non-meshed membranes in above-ground damp proofing applications within the Platinum Damp Proofing System.

Q) What is the difference between the 60mm and 90mm Platinum Cob Plugs?

A) The primary difference between the 60mm and 90mm Platinum Cob Plugs is the fixing depth they achieve within the substrate, which directly affects the anchorage they provide. The 60mm plug, drilled to approximately 65mm, is suited to situations where the substrate is of moderate quality for a cob-style plug and where the shorter embedment provides sufficient grip for the membrane being secured. The 90mm plug, drilled to approximately 95mm, provides significantly greater embedment and is better suited to more severely deteriorated, soft or unreliable substrates where deeper anchorage is needed to hold the membrane reliably against the wall. The 90mm version is the natural choice wherever any doubt exists about substrate quality or where particularly challenging masonry conditions are encountered during installation.

Q) How are Platinum Cob Plugs installed correctly?

A) To install Platinum Cob Plugs correctly, first inspect the substrate and confirm the membrane is correctly positioned on the wall. Using a 10mm SDS drill bit, drill through the membrane and into the substrate to approximately 65mm depth for the 60mm plug or approximately 95mm depth for the 90mm plug. Where Newtonite 801 Mastic sealing is required, apply mastic inside the fixing head before insertion. Push the plug through the membrane and into the drilled hole, ensuring it is seated squarely. Drive the supplied central pin through the plug body using a suitable hammer, causing the stem to expand against the surrounding substrate and create the mechanical anchorage. After fixing, confirm each plug is secure and the membrane is held tightly and evenly against the wall.

Q) What membranes are Platinum Cob Plugs compatible with?

A) Platinum Cob Plugs are compatible with a wide range of meshed and non-meshed damp proof membranes. Within the Platinum range, they are suitable for Platinum DM2 and DM3 meshed membranes and Platinum PM3 non-meshed membrane. Beyond the Platinum system, they offer compatibility with Newton Newtonite and Newtonite Lath membrane systems, Platon PB2 Mesh Membrane, and Wykamol CM3 and CM3 Mesh Membrane. This broad compatibility makes them a practical fixing option for installers working across different damp proofing membrane brands, particularly on challenging substrates where expanding plug anchorage is needed. Suitability for each specific membrane system and project should always be confirmed against the relevant manufacturer’s guidance and installation instructions before work begins.

Q) What substrates are Platinum Cob Plugs suitable for?

A) Platinum Cob Plugs are designed specifically for weak, friable, undulating or low-density wall substrates where standard fixing plugs are unreliable. Suitable backgrounds include cob construction commonly found in older UK properties, soft historic brickwork that has deteriorated through age, lime mortar movement or moisture exposure, deteriorated blockwork where the block composition is too soft for straight plug grip, and certain friable or irregular stone backgrounds where mechanical expansion can still create useful anchorage. The substrate must be capable of accepting a 10mm drilled hole and retaining the expanded plug stem after pin installation. Where masonry is so severely crumbled or structurally compromised that it cannot support any fixing, localised repairs should be carried out before membrane installation proceeds.

Q) Are there practical tips for getting the best results when installing Platinum Cob Plugs?

A) For the best results when installing Platinum Cob Plugs, inspect the substrate carefully before starting and carry out localised repairs on severely crumbling or unstable masonry. Select the appropriate plug length based on substrate quality, using the 90mm plug wherever conditions are particularly poor. Use a 10mm SDS drill bit and maintain a straight, controlled drilling action to avoid enlarging the hole or further disturbing the surrounding masonry. Position the membrane carefully before drilling to ensure the fixing layout achieves the recommended 16 plugs per m² density. Where higher risk damp conditions exist, apply Newtonite 801 Mastic inside the fixing head before insertion. After driving the central pin, check each plug is firmly seated and the membrane is held tightly and evenly against the full wall area before finishing.

Q) What are the limitations of Platinum Cob Plugs?

A) Platinum Cob Plugs have several important limitations to be aware of. They are designed for above-ground damp proofing membrane fixing and are not suitable for below-ground cavity drain waterproofing applications where a sealed watertight fixing is required. While the expanding-stem action improves grip in weak substrates, the plug still requires the masonry to be stable enough to accept a 10mm drilled hole and retain the expanded stem. Severely crumbling or structurally compromised walls must be repaired before installation. The central pin must be fully driven into the plug to achieve the intended expansion, as partial insertion will result in reduced anchorage. They are not general-purpose wall plugs and should only be used within their intended damp proofing membrane system context.