A multi-layer fluid delivery device for introducing a free-flowing active substance to a structure in situ, said device comprising: a first layer, said first layer having an inwardly facing surface and an outwardly facing surface, said first layer being permeable to said active substance but at least nearly impermeable to a structural construction material to be applied against said outwardly facing surface of said first layer; a second layer, said second layer being water impermeable and having an inwardly facing first side and an outwardly facing second side, said inwardly facing first side of said second layer being affixed directly or indirectly to said inwardly facing surface of said first layer such that all or a substantial portion of said second layer is spaced apart from said first layer to create air space between said first and second layers; a plurality of tubes affixed to and extending outwardly from said first layer, said tubes being adapted to permit inflow of said active substance into said air space; an intermediate layer between said first layer and said second layer wherein said second layer is substantially planar; and said device is characterized in that said intermediate layer comprises a member of the group consisting of (i) a sheet with a plurality of protuberances, (ii) a pair of planar geotextile matrices separated by parallel tubular-shaped geotextile matrices that extend along a major axis of said intermediate layer, or (iii) plural layers of offset polymeric grids; wherein said intermediate layer includes a plurality of interconnected interstitial air spaces sufficient to permit inflow of said active substance between said first layer and said second layer. a first layer, said first layer having an inwardly facing surface and an outwardly facing surface, said first layer being permeable to said active substance but at least nearly impermeable to a structural construction material to be applied against said outwardly facing surface of said first layer; a second layer, said second layer being water impermeable and having an inwardly facing first side and an outwardly facing second side, said inwardly facing first side of said second layer being affixed directly or indirectly to said inwardly facing surface of said first layer such that all or a substantial portion of said second layer is spaced apart from said first layer to create air space between said first and second layers; a plurality of tubes affixed to and extending outwardly from said first layer, said tubes being adapted to permit inflow of said active substance into said air space; an intermediate layer between said first layer and said second layer wherein said second layer is substantially planar; and said device is characterized in that said intermediate layer comprises a member of the group consisting of (i) a sheet with a plurality of protuberances, (ii) a pair of planar geotextile matrices separated by parallel tubular-shaped geotextile matrices that extend along a major axis of said intermediate layer, or (iii) plural layers of offset polymeric grids; wherein said intermediate layer includes a plurality of interconnected interstitial air spaces sufficient to permit inflow of said active substance between said first layer and said second layer.