Soudal Soudafoam Gap Filler Expanding Foam

Health & Safety Recommendations

When using Soudal Soudafoam Gap Filler Expanding Foam, always follow good site hygiene and basic safety practice. Wear suitable protective gloves and safety goggles to prevent contact with skin and eyes, and use protective clothing if there is a risk of splashes. The foam is moisture curing and contains reactive components, so it should only be used in well ventilated areas to avoid unnecessary inhalation of vapours and aerosols.

Before starting work, read the label and the Material Safety Data Sheet in full and keep them available on site. Avoid smoking, naked flames and hot surfaces in the work area and keep the can away from sources of ignition. If you are atomising foam with compressed air or other spray equipment, additional local exhaust ventilation and enhanced personal protective equipment may be required because of the finer mist produced.

In the event of accidental skin contact, wipe away uncured product immediately with a suitable cleaning solvent or foam cleaner, then wash with soap and water. Do not use solvents on large areas of skin. If foam gets into the eyes, rinse immediately with plenty of clean water and seek medical attention. If ingested, rinse the mouth thoroughly with water, do not induce vomiting and contact a doctor. Keep cans out of reach of children and never expose them to temperatures above 50°C. Cured foam must never be burnt or exposed to open flame because it can give off harmful fumes; always remove it mechanically.

Substrate Suitability

Soudafoam Gap Filler is a moisture curing polyurethane expanding foam designed for use on most common construction substrates. It adheres well to masonry, concrete, brick, blockwork, plaster, timber, fibre cement boards and many rigid plastics used in building and roofing applications. The foam is suitable for sealing, insulating and gap filling around pipe penetrations, window and door frames, service entries and general construction details.

It is not recommended for use on low surface energy plastics such as polyethylene (PE), polypropylene (PP) and polytetrafluoroethylene (PTFE), where adhesion is poor. Very smooth or non-porous surfaces may require light abrasion to improve mechanical key, and for unusual or coated substrates a small adhesion test patch should be carried out in advance. Because the foam is cured by moisture, extremely dry, non-absorbent surfaces may benefit from light misting with clean water to promote even curing and optimum bond strength.

Surface Preparation

For best results, all surfaces must be sound, stable and free from dust, loose particles, grease, oil, release agents and other contaminants that could interfere with adhesion. Brush or vacuum away loose debris from joints and cavities and remove any friable material. Where old sealants or failed foams are present, cut them out back to a solid edge before applying the new expanding foam.

Substrates should be brought to the recommended temperature range before application. The surface temperature should be between 5°C and 35°C, with ambient and can temperatures between 5°C and 30°C. In cold conditions, bringing cans up to room temperature improves yield and foam quality. Immediately before foaming, lightly mist the sides of the joint or cavity with clean water using a spray bottle; this assists the moisture curing process and helps the foam achieve its designed density and mechanical properties. On very deep voids that will be filled in layers, repeat this light misting between successive passes.

Application Method

Soudafoam Gap Filler is a gun grade expanding foam and must be used with a suitable foam applicator gun. Before attaching the can, shake it vigorously for at least 20 seconds to homogenise the contents and ensure consistent foam quality. Screw the can onto the gun adapter firmly while holding the gun trigger closed, taking care not to over tighten. Adjust the flow control on the gun so that you can achieve a steady, manageable bead of foam for the specific joint size.

Hold the gun with the can above it and keep the assembly as upright as possible during use. Apply the foam by gently squeezing the trigger and moving the nozzle smoothly along the joint or cavity. The foam has high 3D expansion, so cavities should generally be filled to around 65% of their volume; the material will expand to fill the remaining space as it cures. For very deep holes or large voids, work in several layers rather than attempting to fill the entire depth in a single pass. Lightly mist each layer with water and allow it to expand before adding the next layer.

During application, shake the can regularly to maintain a consistent mix and expansion rate. Avoid overfilling, especially around window and door frames, as excessive foam pressure can distort lightweight elements. After you have finished foaming, close the gun’s flow control, leave the can attached if it still contains product, and store it upright if possible. The DuraValve system helps maintain yield and performance even if the can is occasionally stored or transported on its side, but upright storage is still good practice.

Coverage

A 750ml can of Soudafoam Gap Filler provides a free-foamed volume yield of approximately 28L under standard test conditions and a joint yield of around 22m of a typical joint, as measured to EN 17333-1. Actual coverage on site will depend on joint dimensions, ambient temperature, humidity and the degree of expansion permitted by the joint geometry. Narrow beads in shallow joints will cover a greater linear distance than deep or wide voids where more foam is required.

When planning work, it is sensible to allow a margin for wastage, trimming and any voids that prove larger than anticipated once opened up. Professional foam guns help to minimise waste by giving accurate control over bead size, allowing you to apply only as much expanding foam as each joint actually requires.

Curing Time

Soudafoam Gap Filler is a moisture curing polyurethane foam. At typical site conditions, skin formation occurs in about 10 minutes and cutting time is approximately 25 minutes, both measured in accordance with EN 17333-3. This means that within half an hour of application, excess foam can normally be trimmed flush with a sharp knife or saw.

Full through cure will take longer and depends on joint depth, temperature and humidity. Thin beads in warm, humid conditions will harden more quickly than thick sections in cold, dry air. As a guide, allow at least several hours before applying significant mechanical load or covering the foam with plasterboard, render or other rigid finishes. Maximum temperature resistance of the cured foam is approximately -40°C to +90°C, so it remains stable under normal building temperature cycles once curing is complete.

Cleaning

Uncured Soudafoam Gap Filler can be removed from substrates, tools and the foam gun using a dedicated polyurethane foam cleaner such as Soudal Gun & Expanding Foam Cleaner. Always test the cleaner on an inconspicuous area first, as some plastics, paints and lacquered surfaces can be sensitive to strong solvents. Wipe away softened foam with a clean cloth and repeat as necessary while the product is still fresh.

Once the foam has fully cured, it can no longer be dissolved by cleaning agents and must be removed mechanically using a knife, scraper, saw or abrasive method. For stubborn residues and detailing work Soudal Cured PU Remover may be used, subject to compatibility with the underlying surface. After finishing the job, purge the foam gun with cleaner according to the gun manufacturer’s instructions so that the applicator remains ready for future use.

Limitations

Soudafoam Gap Filler is not UV resistant and should not be left permanently exposed to direct sunlight. Once cured and trimmed, it should be protected with a suitable sealant, paint, plaster, cladding or other covering to maintain long term performance. It is not recommended for bonding or sealing polyethylene, polypropylene or PTFE, and should not be used in continuously wet or submerged conditions without additional protection.

The product is a gap filling expanding foam and is not designed as a structural anchor for heavily loaded fixings or as a substitute for mechanical fasteners in critical applications. Although it has useful compressive, shear and tensile strengths, any structural design must rely on appropriate mechanical means with the foam playing a secondary role. It should not be used as a fire stopping system unless part of a specifically tested and approved detail.

Other Information

Soudafoam Gap Filler is based on a moisture curing polyurethane system with a stable, thixotropic foam consistency. Typical free foamed density is about 27kg/m³, with compressive strength around 21kPa, shear strength around 33kPa and tensile strength around 79kPa, giving a robust yet workable cured foam. Elongation at maximum force is approximately 11%, which allows the foam to accommodate minor movement without cracking.

The foam provides excellent acoustic and thermal performance, with sound insulation of around 58dB (EN ISO 717-1) and thermal conductivity of approximately 0.037W/mK (EN 12667). Shrinkage after curing is less than 2% and there is no significant expansion after cure, which helps to protect adjacent components from unwanted movement. For storage, keep cans upright where possible in a cool, dry, frost free place and avoid temperatures above 25–30°C for prolonged periods. When used in accordance with these instructions, Soudafoam Gap Filler Expanding Foam provides a reliable, professional solution for gap filling, sealing and insulating in a wide variety of construction and maintenance projects.

Q) What is Soudal Soudafoam Gap Filler Expanding Foam and what is it used for?

A) Soudal Soudafoam Gap Filler Expanding Foam is a professional gun grade polyurethane foam used for fast gap filling, sealing and insulation in construction and maintenance work. It is a one component, moisture curing foam that expands in three dimensions to fill voids, joints and irregular cavities. Once cured it forms a rigid, closed cell structure that provides mechanical support, thermal insulation and sound reduction. It is commonly used around frames, pipes, services and openings where draughts, heat loss and noise need to be controlled. Both trade and competent DIY users can use it with a suitable foam gun.

Q) How does Soudal Soudafoam Gap Filler Expanding Foam work once it is dispensed?

A) Soudal Soudafoam Gap Filler Expanding Foam is dispensed from a pressurised can through a foam gun as a liquid foam that expands rapidly on contact with air and surface moisture. During curing, it continues to expand to fill gaps up to roughly two thirds prefilled volume, then hardens into a rigid polyurethane foam. The cured foam has a closed cell structure that resists air movement, conducts heat poorly and dampens sound transmission. It adheres strongly to most building materials without primer. After curing, it can be trimmed, cut and finished before being covered with suitable finishes.

Q) Where can Soudal Soudafoam Gap Filler Expanding Foam be used around the home or on site?

A) Soudal Soudafoam Gap Filler Expanding Foam is versatile and suitable for many interior and some sheltered exterior applications. Typical uses include sealing pipe and cable penetrations, closing voids around services, filling irregular holes in masonry and blockwork and sealing gaps in lofts and roof voids. It is also useful for perimeter sealing around rigid insulation boards and for acoustic treatment of joints and penetrations in partitions and ceilings. It should always be overcoated or covered where exposed to sunlight or mechanical damage to maintain performance.

Q) Which substrates are suitable for Soudal Soudafoam Gap Filler Expanding Foam and which should be avoided?

A) Soudal Soudafoam Gap Filler Expanding Foam adheres well to most common construction materials such as brick, block, concrete, masonry, plaster, timber, fibre cement boards and many rigid plastics used in building. It provides primerless adhesion on these surfaces, simplifying preparation. It is not suitable for bonding onto low surface energy plastics like polyethylene, polypropylene or PTFE, where adhesion is very poor. Very smooth or coated surfaces may benefit from light abrasion to improve key and a small test area is always recommended on unfamiliar substrates. It should not be used in permanently submerged or continuously wet situations without additional protection.

Q) How should surfaces be prepared before applying Soudal Soudafoam Gap Filler Expanding Foam?

A) Surfaces must be clean, sound and free from dust, loose material, grease, oil, release agents and old, failed foam or sealant. Loose debris should be brushed or vacuumed from joints and cavities so the foam can bond directly to solid material. Where old foam is present, it should be cut back to a firm edge. Substrates must be within the recommended temperature range and not frozen or waterlogged. Because the foam cures using moisture, lightly misting the sides of the joint with clean water before application improves cure and foam structure, especially on very dry or non-absorbent backgrounds.

Q) What is the correct way to apply Soudal Soudafoam Gap Filler Expanding Foam with a foam gun?

A) Before use, the can of Soudal Soudafoam Gap Filler Expanding Foam must be shaken vigorously for at least twenty seconds to homogenise the contents. The can is then screwed onto the foam gun with the trigger closed, and the flow control adjusted to give a manageable bead. Holding the gun with the can above it, the foam is applied smoothly along the joint or into the cavity, generally filling only around two thirds of the space to allow for expansion. For deep voids, the foam should be applied in layers with light misting between passes. Regularly shaking the can during use maintains consistent performance.

Q) How much will one can of Soudal Soudafoam Gap Filler Expanding Foam cover?

A) A standard 750ml can of Soudal Soudafoam Gap Filler Expanding Foam yields approximately 28L of cured foam in free expansion under test conditions. In practice this equates to around 22m of a typical joint as measured to EN 17333-1, though actual coverage will vary with joint dimensions, temperature and humidity. Narrow, shallow joints will allow a greater linear length than deep voids or wide gaps, which take more material. When estimating, it is sensible to allow a margin for trimming, wastage and voids that prove larger than expected once opened up. Using a gun helps minimise unnecessary over-application.

Q) How long does Soudal Soudafoam Gap Filler Expanding Foam take to cure and when can it be trimmed?

A) Soudal Soudafoam Gap Filler Expanding Foam skins over in roughly ten minutes in typical conditions and reaches cutting hardness at about twenty five minutes, both based on EN 17333-3 test methods. At this point, excess foam can usually be trimmed flush with a knife or fine saw. Full cure through the entire depth of the bead or plug takes longer and depends on humidity, temperature and section thickness. Thin beads in warm, moist air will cure quicker than thick masses in cold, dry conditions. It is best to allow several hours before applying significant load or rigid finishes over the foam.

Q) What thermal and acoustic benefits does Soudal Soudafoam Gap Filler Expanding Foam provide?

A) Soudal Soudafoam Gap Filler Expanding Foam forms a closed cell, rigid polyurethane structure that provides both thermal and acoustic improvements where gaps would otherwise exist. The declared thermal conductivity is about 0.037W/mK, so it helps reduce heat loss through joints, penetrations and irregular voids when used to supplement conventional insulation. Acoustically, the foam achieves an insulation value of about 58dB according to EN ISO 717-1, significantly limiting sound transfer through gaps, service openings and linear joints. Used correctly, it contributes to better overall comfort by addressing draughts, cold spots and noise paths that standard sealants alone cannot manage.

Q) Is Soudal Soudafoam Gap Filler Expanding Foam safe and what protective equipment should be used?

A) Soudal Soudafoam Gap Filler Expanding Foam is a professional polyurethane foam and must be handled carefully. It contains reactive components that are moisture curing, so good ventilation is important to minimise inhalation of aerosols and vapours. Users should wear suitable chemical resistant gloves and safety goggles to avoid skin and eye contact, and protective clothing where splashes might occur. Smoking, open flames and hot surfaces should be kept away from the work area as the propellant is flammable. In case of accidental contact with skin or eyes, uncured foam should be removed promptly and the affected area washed thoroughly, seeking medical advice if irritation persists.

Q) Can Soudal Soudafoam Gap Filler Expanding Foam be used safely around window and door frames without causing distortion?

A) Soudal Soudafoam Gap Filler Expanding Foam provides high 3D expansion and excellent stability without significant post expansion once cured, but correct application is still important around frames. The key is to avoid overfilling and to work in controlled passes, allowing the foam to expand into the gap rather than forcing the frame outward. With a foam gun, bead size and placement can be accurately controlled so that expansion pressure remains modest. Filling roughly two thirds of the void and working in layers on deeper gaps helps prevent undue stress. Once cured and trimmed, the foam supports improved airtightness and insulation around the frame without distortion.

Q) How should deep voids or large cavities be filled with Soudal Soudafoam Gap Filler Expanding Foam?

A) For deep voids, large holes or wide cavities, Soudal Soudafoam Gap Filler Expanding Foam should be applied in stages rather than attempting to fill the entire volume in one go. A first layer is applied to around half to two thirds of the depth and lightly misted with clean water to support curing. After expansion and initial set, further layers can be added, each allowed to expand and stiffen before the next is applied. This layered approach ensures more even curing, reduces the risk of voids within the foam and helps control expansion pressure on surrounding materials. It also produces a more uniform, stable finished fill.

Q) How is uncured and cured Soudal Soudafoam Gap Filler Expanding Foam cleaned or removed?

A) Uncured Soudal Soudafoam Gap Filler Expanding Foam can be removed from tools, surfaces and the gun using a dedicated polyurethane foam cleaner such as Soudal Gun & Expanding Foam Cleaner. The cleaner softens the fresh foam so it can be wiped away with a suitable cloth. Once the foam has fully cured, it is no longer soluble and must be removed mechanically using a knife, scraper, saw or abrasive method. On delicate surfaces, a specialist cured PU remover may be used with care after testing. Foam guns should always be flushed with the recommended cleaner after use to keep them functioning properly.

Q) Are there any limitations to where Soudal Soudafoam Gap Filler Expanding Foam can be used?

A) Soudal Soudafoam Gap Filler Expanding Foam is not UV stable and should not be left permanently exposed to direct sunlight. After curing and trimming it must be protected with paint, sealant, plaster, render, cladding or another covering. It is not suitable for bonding or sealing polyethylene, polypropylene or PTFE, and is not intended for permanently submerged or constantly wet environments without additional protection. It is a gap filler and insulator rather than a structural anchoring system, so it must not be relied on as the primary fix for heavy loads. It should also not be used as a fire stopping solution unless part of a tested system.

Q) Is Soudal Soudafoam Gap Filler Expanding Foam suitable for DIY users as well as professionals?

A) Soudal Soudafoam Gap Filler Expanding Foam is a professional gun grade foam, so it is widely used by tradespeople who need precise application and high yield. However, competent DIY users who are comfortable using a foam gun can also benefit from its performance and control. The gun format allows more accurate dosing than traditional straw foams, reducing mess and waste in domestic projects. DIY users must still follow all safety guidance, including wearing gloves and goggles and working in well ventilated conditions. For those who already own or are prepared to invest in a foam gun, it provides a very controllable, efficient foam option.

Q) Can Soudal Soudafoam Gap Filler Expanding Foam be plastered, rendered or painted over once cured?

A) Yes, once Soudal Soudafoam Gap Filler Expanding Foam has fully cured and been trimmed flush, it can be covered with many common finishing materials. Plasterboard can be fixed over it, and suitable plasters or renders can be applied onto adjacent solid backgrounds with the foam acting as a backing in the gap. The exposed foam should generally be primed or sealed where it will meet wet finishes to improve adhesion and prevent excessive suction. It can also be painted with most standard decorative paints after priming if small areas remain visible. In all cases, ensure the foam is fully cured and stable before finishing.

Q) What is Soudal’s DuraValve technology and how does it benefit Soudafoam Gap Filler Expanding Foam users?

A) Soudal’s DuraValve technology is an advanced valve system built into the can of Soudafoam Gap Filler Expanding Foam to maintain optimum performance throughout its shelf life. Traditional foam valves can sometimes give inconsistent output, especially if cans are stored horizontally or ageing. DuraValve helps maintain consistent flow, expansion and yield even when cans have been transported or stored on their side, which is common on busy sites and in vans. For users, this means more predictable expansion, better utilisation of the product in each can and fewer surprises when using cans that have been on the shelf for some time.

Q) How should Soudal Soudafoam Gap Filler Expanding Foam cans be stored for best performance and shelf life?

A) Soudal Soudafoam Gap Filler Expanding Foam cans should be stored upright where possible in a cool, dry, frost free environment, away from direct sunlight and heat sources. Prolonged exposure to temperatures above around 25–30°C can reduce shelf life and affect foam quality. The DuraValve system helps maintain performance even if cans are occasionally stored or transported horizontally, but correct storage remains good practice. Cans must never be exposed to temperatures above 50°C or left near open flames because they are pressurised and contain flammable propellant. Always check the expiry date and shake cans vigorously before use to ensure the foam is properly mixed.

Technical Data Sheet

Safety Data Sheet