Pre-Design Criteria
These guidelines walk through key criteria to consider before you begin designing with Nudura® ICFs, including wall thickness, general layout, engineering parameters and wall function.
These guidelines walk through key criteria to consider before you begin designing with Nudura® ICFs, including wall thickness, general layout, engineering parameters and wall function.
This simple reference matrix assists engineers, designers, and contractors in selecting an appropriate form thickness of Nudura Insulated Concrete Forms (ICFs) for budget, quotation or preliminary design consideration purposes only. The recommendations contained in this document are intended as a general guideline only and are not a substitute for proper Engineered design to ACI 318 (USA) or CAN/CSA A23.3 (CAN) Standards.
Note that local contributing factors such as high clay content in soils, seismic activity, or high wind pressures may dictate the selection of a thicker core form. In most cases, the proposed recommendations herein will result in optimum reinforcing patterns capable of resisting the required loadings for each scenario.
When transitioning from traditional wall systems to ICFs, designers must consider several essential elements when planning layouts. The primary consideration revolves around the 2 5/8-inch (67 mm) thick EPS (Expanded Polystyrene) insulation panels on each side of the concrete core wall.
The overall building length and width, as well as the total thickness of the concrete wall, must reflect the thickness of both EPS insulation panels. When using Nudura’s wall technology for interior demising walls, the EPS insulation on each face of the concrete wall will affect the overall square footage of floor space, so plans should appropriately allow for this extra wall thickness.
Nudura offers custom-cut radius forms to suit the designer's needs for a building. Radius walls can also be created by field cutting the 8-foot (2.44 m) straight panels and insert webs. When incorporating these wall types into a drawing, the designer needs to keep in mind that, for estimating and cutting purposes, dimensioning should include the radius dimension and the number of degrees the radius will turn based upon a circle (360°).
For elevation planning purposes, the Nudura form unit is based on an 18-inch (457 mm) height, which was selected for efficient horizontal reinforcement spacing in a commercially-constructed 6-inch (152 mm) core concrete wall.
Stack heights with ICF construction can be particularly important, especially when considering things such as:
Commercial contractors regularly working with Nudura wall systems will plan their stack heights to suit the elevation layout requirements of the building as assigned by the architect. Here are some additional design tips for greater ease of construction:
Under most building code bodies, Nudura is classified as a “Flat Wall ICF System”, meaning that it enables the creation of flat monolithic structural reinforced concrete walls.
This section presents data pertinent to the building performance aspects of the Nudura wall system, including links to details, testing or certifications that verify code compliance in the following areas:
STC ratings of walls will vary exponentially in proportion to a wall’s thickness. Codes in both the USA and Canada are specific about required ratings of performance for sound attenuation between suites and along corridors in multi-tenant residential, and hotel or office suite applications. The accepted minimum standard requirement is STC 50 for between suites and along corridors and STC 55 for separations around garbage chutes and elevator shafts of these kinds of buildings.
When considering the selection of forms for demising or tenant separation walls between suites and along corridors, the minimum concrete core thickness wall needs to be 6-inches (152 mm). Take into consideration the effects that less than perfect consolidation may contribute to the degradation of wall acoustic performance. Even cutouts for electrical and plumbing may adversely affect this performance.
According to the Portland Cement Association’s Book entitled “Insulating Concrete Forms for Residential Design and Construction”, typical ICF walls with an STC classification ranging between 44 to 58 “allow less than 1/3 of the amount of sound through that a typical frame constructed wall assembly with an STC rating of 36 would”.
On this basis, the average individual might be tempted to conclude that if an ICF wall reduces sound to 1/3 the level of that of a frame wall (up to 3 times more sound dampening capability), the resulting STC rating of the ICF should be 3 times the numeric value of the frame wall (STC 36 X 3 = 108).
The numeric classification of STC is based on a “logarithmic” scale which means that sound dampening capability exponentially increases as wall thickness and/or density increases. This explains why incremental adjustments in mass and thickness to a wall profile through the addition of finish or mass in concrete can have dramatic effects on overall sound dampening capability.
Based on Nudura STC testing, the following rules should be considered when constructing STC rated walls:
For a copy of Nudura’s STC documentation, click on the link below:
The Nudura ICF wall system, when installed per UL/ULC listings, has an established Fire-Resistance Rating Listing in Canada and Classification in the USA.
When specifying Nudura® forms for the construction of either load-bearing exterior structural walls or load-bearing or non-load-bearing fire separation walls between suites or along corridors, the following detail specifications are applicable. Note: All walls must comply with both concrete and steel specifications as outlined in each of the ULC/UL Listings/Classifications.
Note: The gypsum wallboard on the exterior face of the exterior wall may be omitted provided the EPS insulation is protected in accordance with building code requirements.
Though not a requirement for exterior walls in Canada, the Architect or Engineer should note that if buildings are more than 18 meters (59 feet) in height and not sprinklered, per Section 3.1.5.12(4) of the Code, any interior only walls in buildings as described above, containing foam plastic insulation must be protected with Type X Gypsum board not less than 15.9 mm in thickness, in lieu of the 1/2" regular gypsum board that is prescribed in the above-noted tests. This is a requirement for additional thermal barrier protection ONLY, not a requirement for fire-resistance rating.
Additional questions with respect to Nudura Fire Resistance Testing can be directed to the Nudura distributor in your region.
A common question asked by design professionals with respect to ICF construction is whether an additional vapor barrier or vapor retarder is required to be applied over the interior surface of the Nudura Insulated Concrete Form System.
The clauses of most American Building Codes (including the International Code Family) are structured in such a way that they provide for the fact that plain and reinforced concrete or masonry walls constructed in accordance with the Code (or constructed of materials that are not susceptible to damage from moisture) are not required to have additional vapor retarder materials applied to them. As specified under Sections 1405.3 and IRC Section 601.3, Class I, II or III Vapor Retarders are required on the interior side of frame walls only. For reference under these Codes, although not required for concrete walls, Nudura EPS Foam qualifies as a Class II Vapor Retarder (see additional information below). According to International Code Definitions (under both Codes), a Class II Vapor Retarder is any material providing vapor permeance falling between 0.1 perm and 1.0 perm.
In Canada, vapor barrier requirements are specified under Section 9.25.4 of the National Building Code (NBC) and all applicable Provincial Building Codes. As the risk of damage to building structural elements resulting from condensation is much greater than in the USA, this section requires that a vapor barrier be provided to the interior surface of all insulated walls, ceilings, or floors (regardless of whole wall material composition). The requirements under the 2010 National Building Code have been expanded to provide that the vapor barrier element can be provided by a variety of building material types (thus not restricted to simply film materials). Under Section 9.25.4, a Vapor Barrier must limit vapor permeance to a maximum of 60 ng.Pa.s.m2 (nanograms per Pascal second meter squared) or 0.780 Perm. (this is consistent with the middle range of performance of a Class II Vapor Retarder under the American International Codes).
The IAS and SCC accredited testing agency, Intertek/ETL Semko has confirmed that the calculated vapor permeance of 2 5/8-inch (67 mm) thickness of Nudura foam on the interior panel of the concrete wall assembly achieves a maximum vapor Permeance of 36 ng/Pa.s.m2 or 0.624 Perm, and therefore falls under the maximum allowable vapor permeance set forth by the Canadian Codes and even though not necessary over concrete walls, qualifies the EPS foam as a Class II Vapor Retarder under American Codes as well. Remember that this rate has been determined independently of any resistance to vapor permeance than the monolithic concrete wall itself provides within the wall assembly. If required, more detailed information on these compliances can be obtained at the following links:
Within ASTM E1677-95, the standard states that an air retarder or barrier is “a material or system in building construction that is designed and installed to reduce air leakage either into or through the opaque wall.” The test standard goes on to say that air barrier materials must have air permeability not greater than 0.06 cfm/ft2 (0.3046 liters/second/m2) under a pressure differential of 0.3 in. (7.62 mm) water. Air Barrier products such as wraps, or self-adhering membranes will generally have air leakage permeability ranging from 0.0022 - 0.71 cfm/ft2 (0.0112 – 3.607 liters/second/m2) under the pressure differential of 0.3 in. (7.62 mm). Monolithic concrete has no measurable air permeability or leakage.
Since Nudura’s ICF technology is comprised of two 2 5/8-inches (67 mm) thick (67 mm) panels with a minimum of 4” (102 mm) of monolithic concrete in the center, the complete wall assembly acts as an air barrier with low air permeability and leakage, falling below the standard requirements outlined in the ASTM test standards. This does not differ due to various regions or climatic zones where Nudura ICFs may be used.
Nudura has been qualified as an air barrier through Construction Technology Laboratories (CTL) Engineering in Skokie, Illinois. A copy of this documentation can be downloaded below:
Insulated Concrete Form Systems in buildings of Non-Combustible Construction imposes specific code compliance requirements for the protection of foam plastic when installing on the building's exterior.
In the USA, the ICC lists the approved materials in Nudura’s Evaluation Report ESR-2092, and confirms that the following exterior finishes are approved for application to Nudura ICFs in Non-Combustible Construction:
In addition to the above-noted options for finishing exterior surfaces of buildings designated for non-combustible construction, there are limited single-story occupancies of Types I through IV Construction within the USA where a design professional is asked to consider use of Nudura® and the client may not wish to employ Brick, Hard Coat Stucco, or Non-Combustible EIFS as the designated finish, even though the occupancy type and building size DOES NOT require the provision of an automatic sprinkler system. Nudura’s Evaluation Report No. ESR-2092 makes specific provisions for the enabling of use of either Aluminum or Steel Siding Finish (without the need of an engineer designed cladding system or additional requirement of automatic sprinklers) so long as it is installed as per the limitations stated within the report.
In Canada, for Non-Combustible construction with exterior finishes, materials must conform to CAN/ULC S-101 “Fire Endurance Tests of Building Construction and Materials” and CAN4-S114-M, “Test for Determination of Non-Combustibility in Building Materials”.
The list below shows exterior finishes that either comply or have been tested to the standard above:
This section has been designed to provide the required data to enable Design Professionals to detail firewall connections with Nudura® Forms that are fully compliant with North American Codes as outlined below.
Firewalls are detailed under the following Sections of Existing North American Codes:
The performance requirements for firewalls can be summarized under the following main criteria. (Regardless of the following summary, the design professional must always refer to the above Sections for exact compliance to the Code requirements for his/her region):
The details located in the above grade combustible construction section are designed to achieve the above-noted objectives. This specific detailing ensures that the EPS foam does not breach the continuity of the fire separations. The interconnecting floor and roof structures are also designed to collapse safely away from the firewall such that they will NOT contribute to the wall’s collapse.
For additional documentation or information with respect to the application of Nudura ICFs for firewall applications, you can contact your local Nudura representative or distributor.
