KNOWLEDGE · WATER AND UNDERGROUND STRUCTURES

Curtain injection: a barrier behind the structure

The curtain must connect sealed zones on the ground side. Success depends on the injection location, the actual material path and continuity at the repair boundaries.

Assessment Procedure and options Selection and next step

EXPLORE THE METHOD

Curtain injection: from access through the structure to a continuous barrier

The sequence moves from the full cross-section through drilling and preparing holes to controlled injection. The curtain must form behind the structure, in the ground zone. The visible packer grid and material consumption alone do not prove its continuity.

Cross-section of brickwork, stone masonry and concrete connected to a slab; the blue barrier runs along the ground side. — The target zone lies outside the structure, including at the wall–slab junction.

01 · Cross-section

View the target barrier behind the wall and slab

Boreholes pass through the structure and deliver material to the ground contact zone. The blue band shows the objective: connecting the seal behind the wall and beneath the slab. Corners, penetrations and edges need the same attention as the centre of the repair area.

Select AcrylGel considering the mixture variant and moisture conditions. HydroGum is a possible curtain injection option following individual selection and a trial: distribution, water availability for the reaction and confinement of the expanding foam fill must be confirmed. Both materials require their own application methods.

Identify the barrier boundaries on the cross-section.
Identify possible paths around the curtain.

AcrylGel variants →HydroGum →Saturating the wall structure →

Boreholes in the wall and slab lead to the ground on the other side of the structure. — The borehole outlet determines where the material acts, not just the entry point.

02 · Preparation

Create an injection path to the zone behind the structure

The hole must deliver material behind the structure. Set it out using the actual thickness and structural arrangement, accounting for reinforcement, services and the direction of access to the ground zone.

The 15–40 cm dimensions in the illustration relate to an indicative grid. Spacing must be selected through a trial in the specific substrate. A hole ending within the wall may saturate its structure, which does not confirm formation of a curtain outside it.

Confirm the borehole path and depth.
Distinguish the injection location from the packer position.

Trial grid and method →

Flushing a borehole with water; the blue arrow leads to its external outlet. — The blue arrow in this illustration represents water used to prepare the hole.

03 · Preparation

Clean the holes and check the flow path

Remove drilling debris from the injection path. Water flushing prepares the hole before actual injection. Adapt the method and intensity to the condition of the structure and substrate.

Check that the hole is clear and observe where water emerges. Unexpected outlets may indicate communication with a void or another space. Preparing a hole is neither a watertightness test of the completed curtain nor confirmation of the future injection material's reach.

Provide controlled collection of discharges.
Record the communication paths revealed.

Assessment of the substrate and possible escape paths →

View of packers from the brick wall side, with injection points continuing across the slab. — The brick masonry option shows access points; the curtain zone is behind the wall.

04 · Substrate option

Substrate option: grid on brick masonry

Plan injection and observation points in relation to the actual masonry and slab junction. The packer must be securely installed, and the injection path must reach the external zone. Material uptake by bricks or mortar joints alone does not confirm formation of a curtain.

The 15–40 cm spacing shown is an example. Select it on a trial section, checking the effects of the ground, voids and possible escape paths. This illustration and the next one showing concrete are substrate alternatives, not two stages of a single repair.

Check masonry condition and packer stability.
Confirm communication in the zone behind the wall.

Application trial →

View of packers from the concrete wall and slab side, with indicative point spacing. — The concrete option requires assessment of the structure and continuous access at the wall and slab.

05 · Substrate option

Substrate option: grid on concrete

In concrete, plan points accounting for reinforcement, services and the actual element thickness. Include the wall–slab junction so that the barrier does not stop before the corner.

The 15–40 cm spacing belongs to the option shown. Coverage behind the concrete depends on the ground and material path, so the grid must be checked by a trial. This view is an alternative to brick masonry; it does not represent an additional stage after injecting the masonry.

Account for reinforcement and services.
Check the connection between vertical and horizontal sections.

Grid trial →

Injection into a packer, a blue zone on the ground side and material emerging at adjacent open points. — Observing communication allows comparison of the injection location with the actual material path.

06 · Injection

Inject material and observe communication

In this illustration, blue now represents sealing material, not the water used during flushing. Injection into a selected point and observation of adjacent holes help track the spread of the injection material. Combine these observations with uptake, time and pressure.

If there is uncontrolled escape, a sudden uptake change or a pressure increase without flow, stop injection and identify the cause. Reaction time must allow zones to connect without letting material escape beyond the planned area. The trial establishes this balance in the actual substrate.

Record the sequence and communication locations.
Check drains and other possible escape paths.

Controlling the curtain injection process →Cleaning after the selected injection material →

View from the ground side with overlapping yellow material zones behind the wall. — The shapes show intended continuity between zones, not a guaranteed material shape in the ground.

07 · Inspection

Check overlapping coverage and curtain boundaries

Every point should contribute to a continuous barrier. The overlapping shapes in the drawing illustrate the need to connect areas of coverage. The actual shape depends on the ground, voids, water and injection procedure; the illustration colour does not identify a specific product.

Acceptance covers the entire area, corners, the slab junction and adjacent waterproofing. If a leak moves to an adjacent location, check whether water can bypass the barrier. Document supplementary work and assess watertightness under water conditions representative of service; consumption alone does not confirm continuity.

Check barrier boundaries and connections.
Separate material quantities from proof of watertightness.

Curtain injection acceptance →Ground: other injection objectives →

Where should the barrier form?

An injection curtain forms outside a wall or slab, usually at the interface between the structure and the ground. Material is injected through the structure from the accessible side. The solution can be considered where restoring external waterproofing is difficult and assessment allows controlled sealing to be planned.

This is a different objective from saturating the wall structure. Material remaining in masonry pores and joints does not yet mean a barrier has formed behind it. Establish the target zone on a cross-section before selecting borehole lengths and material volume.

The ground is not a uniform mould

Identify the soil type and layers, voids beside the structure, water level and possible escape points. Backfill, a gap beside a wall and cohesive soil may take up material in completely different ways. In a drain or an unconfined void, it may travel far beyond the planned area.

Mark the curtain boundaries: wall–slab junction, corners, penetrations and adjacent waterproofing. A barrier ending before such a detail leaves water a way around it. The repair extent should follow the water ingress path, not just the damp patch area.

Establish the grid through a trial

Choose a section covering representative ground and an important boundary detail. Holes should reach the zone behind the structure; drilling must account for reinforcement, services and the actual cross-section. Clean the injection path, install packers and arrange controlled collection of discharges.

During the trial, compare material quantity, injection time, communication between points and water behaviour. Also check whether material appears in drains or other unintended locations. Use the results to refine spacing, sequence, reaction time and section size.

Two different reasons to change the method

Gel escapes before setting

There may be an open escape path or a reaction time too long for the flow conditions. Identify and restrict that path, or select a preliminary stage. A faster reaction without assessment may only seal the nearest point.

The material does not connect the zones

Check the borehole outlet location, clear passage, geometry and soil type. A different grid or method may be required. Do not assume that higher pressure will create an even curtain in every substrate.

Uptake is much greater than in the trial

Look for a change in soil, a cavity or communication with a distant space. Stop extrapolating the original consumption and redefine the section boundaries.

The leak disappears but appears nearby

Water may have found a new path. Assess barrier continuity and its connections before considering the repair area complete.

Select the gel variant for the environment

AcrylGel can be prepared with polymer or with water in mixture B. These are not names for the same formulation. For a curtain, selection includes moisture conditions, water retention in the gel, expected movement and washout risk. The variant with water is described for curtains in ResinBau materials; select it based on assessment of the zone.

With intense inflow or large voids, consider a stage that limits escape before applying the main material. Foaming in free space does not indicate how much product will remain in the ground or whether a continuous barrier will form.

Consumption is a process outcome, not proof of continuity

Establish quantities from the trial section separately for different substrates. Retain the unit, variant and material concentration; kilograms of product, litres of ready-mixed material and the volume of the ground zone are not interchangeable. An indicative quantity per square metre cannot replace a trial.

Document points, communication, interruptions and adjustments. Acceptance covers the entire zone and its edges, and inspection should reflect representative water conditions. A changing water level may reveal a path that was inactive during the works.

RESINBAU SELECTION

Calculate what you know

CALCULATORMixing AcrylGel →

Select a variant, then check the reaction on a sample under site conditions.

CALCULATORLitres–kilograms quantities →

Convert material quantities from the trial; the calculator does not determine curtain coverage.

Next step

Discuss your project conditions

Prepare a cross-section, a description of water and movement, and results of previous trials. ResinBau helps select the material and application method.

Discuss your project / technical selection ↗