Gulf Coast Community Design Studio intern architect Samuel Carlsen presented new research findings and design proposals related to dry flooodproof construction at the annual conference of the Floodplain Management Association. The presentation was titled “Dry Floodproofing in Commerical Construction in Coastal Areas: A Future Role in Flood Mitigation.” The conference was held in San Diego from September 6th through the 9th.This presentation was part of on-going work funded by the Southeast Region Research Initiative (SERRI) to research methods for improving the effectiveness, affordability and community integration of dry floodproof construction techniques.
After making revisions to the test pods after flood simulation 1 for the SERRI Dry Floodproof Construction Research project, the GCCDS performed the second full test flood simulation June 28th, 2011. For a 24-hour period, six test pods (shown above), which are full-size mock-up wall assemblies of various commercial construction wall assemblies, were subject to a 3-foot flood, to simulate anticipated hydrostatic pressure on buildings during a major coastal flood event. During the testing period, measurements were taken to record the depth of water that was able to penetrate the wall assemblies. The working definition of dry floodproof construction, per the USACE, states that waterproof construction shall be “permitted the accumulation of [no] more than four inches of water depth in such space during a 24-hour period if there are no devices provided for its removal…”. Thus, it was considered that a well-performing test pod during the flood simulation would have an interior water depth of less than four inches over the testing period. Four test pods demonstrated performances compliant with dry floodproof construction standards during this testing period. Below is a summary of the results for each test pod during flood simulation 2.
Test Pod A: Sealed BlockTest Pod A: Sealed Block was constructed of a basic CMU block wall with an exterior sealant applied to the exterior face of the wall. The sealant was comprised of three layers: two layers of silicone modified polyurea sealant sandwiching a layer of closed cell spray foam insulation. This type of sealant is generally found in industrial applications, used as lining for storage tanks designed to hold corrosive materials. This exact wall assembly was tested during flood simulation 1. During flood simulation 2, the results were similar: after 24 hours, the maximum interior depth of water was only 1/4″.
Test Pod B2: Cavity Wall Filled BlockTest Pod B2: Cavity Wall Filled Block was a revision of Test Pod B: Cavity Wall, that was tested during flood simulation 1. During the second flood simulation, all of the cores of the this CMU block wall were filled with grout, to observe if additional mass within the block wall would contribute to overall performance. A fluid-applied asphaltic emulsion coating was painted on the exterior face of the CMU block wall, with a layer of 2″ rigid insulation board continuously attached over this. A 2″ cavity separated the brick veneer exterior of the assembly and the thermal barrier. Test Pod B2 had an improved performance during flood simulation 2 (over Test Pod B in flood simulation 1); however the photo above clearly shows water penetrating the block wall at masonry joints. The flood depth in this test pod after the 24-hour test period was 15 1/2″, demonstrating an assembly that is not viable for floodproof construction.
Test Pod G: Sheet Membrane BlockTest Pod G: Sheet Membrane Block in flood simulation 2 was a retrofit of Test Pod C: Unsealed block that was used in flood simulation 1. Test Pod G was comprised of a CMU block wall with a self-adhering rubberized asphalt/polyethylene membrane sheet applied to the exterior face. Vertical edges of the membrane sheet overlapped at least 2″ to provide a continuous waterproofing membrane. Furring strips on the exterior of the membrane were attached with masonry screws that penetrated the membrane. In an actual building, siding or panels would be attached to these furring strips in a ‘rainscreen’ assembly. However, for observational purposes, the exterior finish was omitted from this test pod during flood simulation 2. This test pod performed well; during the 24-hour testing period, with a maximum interior water depth of 3 1/2″.
Test Pod D2: ICFTest Pod D2: ICF in flood simulation 2 was a retrofit of Test Pod D: ICF used in flood simulation 1. Test Pod D2 was constructed out of ICFs–Insulated Concrete Forms, which are modular units designed to act as both the formwork for a cast-in-place masonry wall and also the permanent thermal barrier, as the forms are made of EPS foam. The retrofit included applying a layer of elastomeric paint to the exterior of the reinforced stucco and thoroughly covering the joint between the slab and the base of the wall. The improvements were a success, as the maximum interior water depth of Test Pod D2: ICF after the 24-hour flood simulation was only 3 3/4″.
Test Pod H: Weatherproofed BlockTest Pod H: Weatherproofed Block was intended to test an assembly demonstrating a minimal approach to dry floodproofing. A CMU block wall was coated with an elastomeric waterproofing membrane, applied with a conventional hand sprayer. This assembly did not perform well; at only four hours into the testing period, the interior water depth had surpassed the 4″ dry floodproof standard. At the end of the 24-hour testing period, the pod had accumulated a maximum interior water depth of 17″, proving that this assembly is not viable for dry floodproof construction.
Test Pod F2: Metal SIPsTest Pod F2: Metal SIPs in flood simulation 2 was a retrofit of Test Pod F: Metal SIPs that was tested in flood simulation 1. This assembly is a simple panel construction, using Structurally Insulated Panels, which are made up of a layer of 4” EPS rigid foam sandwiched between sheets of stainless steel. The panels are attached to a track at the base of the wall, which is bolted to the slab. Vertical joints are sealed with caulk and metal flashing. This type of wall system was explored, as the Metal SIPs are impermeable to water. During flood simulation 1, this wall assembly did not perform well, as the base was not securely fastened to the channel to avoid uplift from buoyancy forces (vertical hydrostatic pressure). The retrofit for flood simulation 2 involved securely fastening the base channel to the panels with more bolts, using additional layers of caulk to seal the channel, and applying butyl tape to vertical and horizontal seams. Test Pod F2: Metal SIPs performed well during this flood simulation; at the end of the 24-hour test period, the assembly had only accumulated a maximum interior water depth of ½”.
Overall, we were happy with the results from flood simulation 2; we were able to identify four assemblies that are viable options for dry floodproof commercial construction, all of varying degrees of affordability and exterior finishing options.
To investigate the performance of different materials and wall assemblies under hydrostatic forces for potential viability for dry floodproof construction, full-scale wall assemblies were constructed and tested for this research. Referred to as ‘test pods’ within the documentation, each was different and built within an outdoor flood tank. Six test pods were observed during flood simulation 1, with flood water depths of 36” for a 24-hour period of time.Water penetration measurements (documented as interior water depth), visual observations, and electronic moisture content readings were collected during the first flood simulation. After the 24-hour simulation, the test pods were left for a drying period of two weeks, during which time moisture levels were measured and documented, using embedded sensors.The flood tank was constructed using Hesco boxes, which are welded wire mesh boxes with a geotextile lining for sand or gravel fill. Each box has a 3’x3’ base and is 4’ tall, linked together to create a 4’x40’x40’ test flood tank. The tank was lined with heavy plastic sheets to increase its ability to hold water. An elevated walkway was installed within the flood tank to provide access for observation during the flood simulation. A large open air tent was installed over the tank for the duration of the simulation and the drying period.The working definition of dry floodproof construction, per the USACE, states that waterproof construction shall be “permitted the accumulation of [no] more than four inches of water depth in such space during a 24-hour period if there are no devices provided for its removal…”.Thus, it was considered that a well-performing test pod during the flood simulation would have an interior water depth of less than four inches over the testing period. One test pod demonstrated a performance compliant with dry floodproof construction standards during this testing period.
Below are summaries of each test pod assembly and the results of flood simulation 1.
Test Pod A: Sealed BlockTest Pod A: Sealed Block was a CMU block wall with a multi-layered polymer membrane for an exterior waterproof coating. The membrane consisted of closed-cell spray foam insulation sandwiched between two layers of modified silicone polyurea. This coating is generally used in industrial applications, as a tank-liner for corrosive materials. The first course of the CMU block wall was filled with grout and a water-resistant additive. Additionally, at the corners and at middle of each wall span, CMU cells were fully grouted.
Test Pod A: Sealed Block performed well during flood simulation 1; the maximum interior water depth over the 24-hour period was only ¼”, making it a viable option for dry floodproof construction.
Test Pod B: Cavity WallTest Pod B: Cavity Wall was a CMU block wall, coated with a fluid-applied rubberized asphaltic emulsion coating. Over this was a layer of 2” rigid foam insulation and an exterior brick veneer finish, separated by a 2” cavity. A nylon mesh mortar deflection system was installed at the base of the brick wall to provide better drainage during the drying period, along with larger-than-standard weep vents. The first course of the CMU block wall was filled with grout and a water-resistant additive. Additionally, at the corners and at the middle of each wall span, CMU cells were fully grouted.
Test Pod B: Cavity Wall had accumulated 36” of interior water depth (equalizing with the flood depth) after 22 hours into the flood simulation, and surpassed the 4” depth after only 4 hours. It was observed that water was penetrating the CMU block wall through masonry joints, not through the blocks themselves.
Test Pod C: Unsealed BlockTest Pod C: Unsealed Block was a CMU block wall wrapped in a weather barrier with a plastic drainage mat to provide a drainage plane between the exterior face of the block wall and a layer of 2” rigid foam insulation. On the exterior of the foam, vertical furring strips (water-resistant composite deck boards) were fastened, to allow for a ‘rainscreen’ installation of fiber-cement panels as the exterior finish. The intention of this wall, similar to Test Pod B: Cavity Wall, was to create a wall assembly that stopped water at the exterior face of the main structure, and allowed water to drain well from the exterior finish assembly during the drying period.
However, the weather barrier failed to resist water penetration, and Test Pod C: Unsealed Block surpassed the 4” threshold after four hours of the flood simulation. The maximum interior water depth of this test pod was 36” (equalized with the flood depth) at 20 hours into flood simulation 1.
Test Pod D: ICFTest Pod D: ICF was a constructed of ICFs (Insulated Concrete Forms), which are modular units designed to act as both the formwork for a cast-in-place masonry wall, and also the permanent thermal barrier, as the forms are made of EPS foam. The exterior of the wall was finished with a high-end reinforced single-coat stucco.
Overall, this wall performed decently, although it surpassed the 4” threshold after 10 hours of the test flood. The maximum interior depth of this test pod was 10 ½”, surprisingly reached after 30 hours (6 hours after the flood tank draining began).
Test Pod E: Metal StudTest Pod E: Metal Stud had a light-gauge steel frame for the structure, with fiberglass batt insulation between studs. The exterior was sheathed with an exterior grade gypsum board, with a weather barrier wrapped on the exterior. Brick was used as the exterior finish material. This wall was intended to be the control wall for the test period, as it represents a typical construction type found in commercial buildings along the Mississippi Gulf Coast that are not intended to be dry floodproof.
As expected, Test Pod E: Metal Stud failed to perform well enough to be considered viable for dry floodproof construction. After less than two hours into the flood simulation, the interior depth had surpassed the 4” threshold; after four hours, the assembly had a maximum interior water depth of 36”, equalizing with the depth on the exterior of the walls.
Test Pod F: Metal SIPs was a simple panel construction, using Structurally Insulated Panels, which are made up of a layer of 4” EPS rigid foam sandwiched between sheets of stainless steel. The panels are attached to a track at the base of the wall, which it fastened to the concrete slab. Vertical joints are sealed with caulk and metal flashing. This type of wall system was explored because the panels are impermeable to water and can serve as both the structure and the finished wall.
This wall assembly did not perform well during flood simulation 1. After four hours, the 4” threshold had been surpassed, and it was observed that water was steadily seeping into the assembly through the base channel. After 12 hours into the testing period, the vertical hydrostatic forces (buoyant forces) of the flood water caused the wall panels to come completely detached from the foundation, and the walls floated free.
Interior Water Depths: Flood Simulation One The information and observations gathered during this first flood simulation were instrumental in the design of the second flood simulation, as it was clear where improvements could be made to retrofit the walls for further testing. Additionally, by testing a myriad of materials and assembly types, we were able to further our knowledge base of viable options for dry floodproof construction methods.