Waterproofing of River Wall | Polyurea
THE PROBLEM
As part of the development of the old riverside storehouse – into residential units – a long term waterproofing solution was required to prevent water ingress, through the river wall and into the basement area below.
THE SOLUTION
This project presented several unique challenges including the following;
- Only four hours of working time per day due to the tidal location
- Chloride contamination of the substrate, with contamination occurring upon each tide
- Poor substrate with missing mortar, blocks and heavy pitting porosity of the wall to be waterproofed
- Evidence of cracking and possible dynamic movement
- Must be environmentally friendly, so as not to contaminate the river water
- UV exposure
Taking the above into account we proposed the application of a spray applied polyurea waterproofing system offering the following benefits;
- Remains fully flexible when cured, meaning that cracks should not reflect in the waterproofing membrane ensuring the building remains water tight.
- Extremely fast curing (approximately 8 seconds), meaning that the polyurea coating could be immersed almost immediately following application
- Solvent free so as not to contaminate the river water
- UV light does not affect the performance of the material
Initially, the wall was prepared by method of pressure washing using our own 5,000 PSI water jetting unit. Not only does this ensure that the surface is clean enough for our waterproofing system to adhere to, but also removes the chloride contaminants which were present. Each day of works on site began with the washing of the area to be treated, in order to remove organic matter and chloride contamination, from the previous tide.
Once clean the refurbishment of the substrate, in preparation for the polyurea waterproofing membrane, could begin. Due to the poor condition of the bricks, along with the missing mortar, it was decided to resurface the entire wall using Flexcrete Marine Mortar S. This material cures very quickly -preventing wash out with the return of the tide – and the thixotropic nature allowed the material to be applied in a single pass.
Following the consolidation of the substrate, the application of the waterproofing system could begin. In each shift the following had to take place;
- Washing of the area to be treated in that shift to remove chlorides and organic matter
- Drying of the area to be treated using roofing torches
- Application of a fast curing polyaspartic primer by brush and roller to prevent outgassing
- Spray application of the polyurea membrane to a thickness of 3mm
- Spark testing of the polyurea coating to check for pin holing
- Rectification of any pin holing, where discovered
We broke the wall area down to manageable sections, enabling waterproofing in shift patterns. We elected to use Specialty Products Incorporated HT100F UB pure polyurea for this waterproofing project. One of the key benefits of the material, for this project, is the ultra bond molecule contained within it. This allowed the joining of each section, completed in sequential days, without having to abrade/re-profile the overlap on the previous days closed out coating.