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Pre Design Criteria

These guidelines walk you through key considerations you need to think about before you begin building with Nudura. Use these recommendations to achieve optimal wall performance for most environments in North America. Read on below to see important criteria to consider when it comes to wall thickness, general layout, wall function, and engineering parameters, as well as some ideas for how best to deal with local contributing factors.

Wall Thickness Chart

This simple reference matrix is produced to assist engineers, designers, and contractors in selecting an appropriate core thickness of NUDURA® forms for optimum wall performance (i.e., to yield the most efficient combination of concrete and steel for necessary condition).

IMPORTANT NOTE: The recommendations contained in this document are intended as a general guideline only and should not be construed as a substitute for proper Engineered design to ACI 318 (USA) or CAN/CSA A23.3 (CAN) Standards.

Instead, this document is intended as a guideline to aid in the selection of an appropriate form thickness for a suggested wall height or building type for budget, quotation, or preliminary design consideration purposes only. Note that special local contributing factors such as high clay content in soils, high seismic velocities or wind pressures in excess of 21 psf (20 mph to 40 mph) or (1.0 kPa) may dictate the selection of a thicker core form if the design condition is close to the maximum heights suggested in this document. In most cases, for North America- the proposed recommendations herein will result in optimum reinforcing patterns capable of resisting the required loadings for each scenario.

  • Form Thickness Selection Chart

    Form Thickness Selection Chart

General Layout Guide

In the move from traditional wall systems to the use of NUDURA® ICFs in construction, there are essential elements for the designer to consider, especially for planning layouts. The most crucial element for the designer to remember is the 2 5/8-inch (67 mm) thick EPS insulation panel 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 2 5/8-inch (67 mm) thick EPS insulation on each face of the concrete wall will affect the overall square footage of floor space. This will not be a problem, so long as the plan appropriately allows for the extra wall thickness. Radius walls can be created by using the 8-foot (2.44 m) straight panels and insert webs.

NUDURA offers factory custom cut radius walls for projects to suit the designer's needs for a building. These radius walls can also be field cut to meet the designer's drawings and can be placed anywhere within a wall length. 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 cycle (360°). 


  • Radius Wall Cut Dimensions

    Radius Wall Cut Dimensions

Wall Height Cart

For elevation planning purposes, the NUDURA® form unit is based on an 18-inch (457 mm) height, which was selected for enabling optimum efficiency in horizontal reinforcement spacing in a commercially constructed 6 inch (152 mm) core concrete wall (3x its thickness).

Stack heights with ICF construction can be particularly important, especially when considering such things as:

  • Footing elevations relative to grade;
  • Brick finishes relative to grade levels;
  • Floor bearing heights relative to finished grade;
  • Floor bearing height relative to each other.

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. However, if the designer desires optimum conditions for ease of construction of NUDURA® on site, here is a list of tips to remember for achieving optimum design for installation of NUDURA® forms:

If a half form achieves optimum stack height within the projected wall assembly from the top of the footing to a parapet, plan to show the half-height form at either the footing or the top of the parapet. Avoid half-height forms at the center of stack height.

For brick ledges, always plan footing heights so that they position the majority of brick ledge around the building at an optimal height relative to the finished grade level (for most regions, this will usually be 6 inches (152 mm) above grade). This will enable the use of the brick ledge form without having to resort to using the less efficient application of brick ledge extensions at a custom height level.

  • Remember that the NUDURA® wall system offers installers the flexibility of both fully assembled forms and individual site assembled panels. All wall floor slab intersections can be accommodated easily on multi-storey NUDURA® installations by the contractor installing a full panel on the exterior and cutting interior panels to suit the height both below and above the slab. These panels are then tied to the exterior using either cut insert webs or height adjuster ties.
  • If an intermediate floor height to a finished bearing condition will require a partial form panel at the top of the wall stack, it is more efficient if the panel is to be cut at 9-inches (229 mm) in height or less. The remaining section of the panel can be cut and used to construct the same portion of the wall elsewhere in the building, resulting in little or no waste.
  • Avoid detailing brick ledges as floor supports in a commercial application. Brick ledges have limited bearing capacities and therefore should not be relied on for carrying commercial floor loads.

Below are optimal stack height charts for planning wall stack heights up to 36 1/2-feet (11.125 meters) in height. Higher wall heights are possible by adding multiples of the form unit height (18-inches (457 mm)) to the 36 1/2-foot (11.125 meters) wall height shown.

  • Nudura Wall Height Charts

    Nudura Wall Height Chart 2006 Imperial

    Nudura Wall Height Chart 2006 Metric

Engineering Parameters

NUDURA® Integrated Building Technology is a stay in place concrete form system that enables design professionals the opportunity to design structures that meet the requirements of the occupants. 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.

Wall Function

This section presents data pertinent to the building performance aspects of the NUDURA wall system. It includes links to details, testing or certifications that verify code compliance in the following area of required wall performance;

  • Fire Resistive Construction
  • Walls Requiring STC Performance
  • Vapor Barrier/Retarder Performance
  • Air Tightness/Air Barrier Performance
  • Compliances for use on Exterior Walls of Type I-IV Construction (USA) and Non-Combustible Construction over three stories in height (CAN)
  • Fire Wall Construction in both Combustible and Non-Combustible Construction

  • STC Ratings Using NUDURA ICF Walls

    STC ratings of walls will vary exponentially in proportion to a wall’s thickness. Codes in both the USA and Canada are very 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 walls requiring STC 50 Classifications- use minimum 6-inch (152 mm) NUDURA® forms filled with min. Type S (siliceous concrete) clad with 1/2-inch (13 mm) minimum regular gypsum board applied both sides.
    • For walls requiring STC 55 Classifications- use minimum 6-inch (152 mm) NUDURA® forms filled with min. Type S (siliceous concrete) clad with a minimum 5/8-inch (16 mm) Type X gypsum board applied both sides. The use of a resilient channel (mounted at 24 inches (600 mm) o/c) before mounting the gypsum board, in these applications would provide further assurance of exceeding the STC 55 rating requirement.

    For a copy of NUDURA®’s STC documentation, click on the link below: 

    6-Inch (152 mm) STC 50 Letter

  • Fire Resistance Rating of NUDURA Walls

    The NUDURA® ICF Wall System when installed as 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 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 NUDURA® through the NUDURA distributor representative for your region.

  • Vapor Barrier Performance of NUDURA ICF Wall Assemblies

    A common question asked by design professionals with respect to ICF construction is whether or not 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:

    American Vapor Retarders
    Canadian Vapour Barrier

  • Air Barrier Performance of NUDURA Wall Assemblies

    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® Integrated Building 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. It falls below the standard requirements as outlined in the ASTM test standards. This does not differ due to climatic zones throughout the various regions NUDURA® Integrated Building Technology is used.

    NUDURA® has been qualified as an air barrier through Construction Technology Laboratories (CTL) Engineering in Skokie, Illinois. Copy of this documentation can be download below;

    NUDURA Air Barrier Documentation

  • Exterior Finish Used in Non-Combustible Construction

    The use of Insulated Concrete Form Systems in buildings of Non-Combustible Construction impose specific code compliance requirements for the protection of foam plastic when installing on the exterior of the building.

    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® Integrated Building Technology in Non-Combustible Construction:

    • Brick Veneer
    • 7/8-inch (22 mm) Hard Coat Stucco
    • Cement Board Siding
    • Dryvit Systems INC., Dryvit Outsulation Exterior Insulation and Finish System as described in ESR-1232
    • Finestone., Finestone Pebbletex, Pebbletex-D, Quik Clad-D, and Impact-R Wall Systems as described in ER-4455
    • Omega Products International INC., Omega Diamond Wall and Diamond Wall PM Insulating Exterior Stucco Systems as described in ESR-1194
    • Senergy LLC., Senerflex, and Senerthik Exterior Insulation and Finish Systems (EIFS) as described in ER-3850
    • Sonowall Stucco Systems., Sonowall Exterior Insulation and Finish Systems as described in ER-5678
    • STO Corporation., STO Classic Exterior Insulation and Finish System (EIFS) and STO Classic EIFS with Gold Guard as described in ER-3906
    • STO Corporation., STO Essence Exterior Insulation and Finish Systems (EIFS) as described in 9642B
    • STO Corporation., STO Essence Exterior Insulation and Finish System (EIFS) and STO EIFS with Gold Guard as described in ER-3617

    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;

  • Constructing Fire Walls Using NUDURA Forms

    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.

    Fire Walls are detailed under the following Sections of Existing North American Codes:

    • USA: International Building Code 2009: Section 706
    • CAN: National Building Code of Canada 2005: Section 3.1.10

    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):

    • Fire Walls must be constructed to ensure that the structure is split into separate compartments.
    • Fire Walls must be structurally stable- sufficient to the point that they will enable collapse of structure on one side of the firewall under full fire attack without causing the collapse of the wall itself and maintaining the required fire-resistance rating for the wall for the full duration of rating that it is required to maintain.
    • For the most part, (subject to specific exceptions) firewalls must extend:
        • through the building vertically from the footing and extend through to and project upward through the roofline as a parapet wall (height projection will vary depending on country and fire resistance rating required) 
        • extend horizontally through the complete depth dimension of the building from exterior wall to exterior wall
        • extend horizontally beyond the exterior walls by a specified minimum distance
        • extend to the outer edge of any projecting elements such as balconies or overhangs
    • Fire Walls Must be constructed so as not to cause any breach of ANY fire separation at floors or Interconnecting walls that provide fire separation between suites or corridors. The details of construction must ensure that whatever fire-resistance rating is assigned to the floor or interfacing wall separation, the rating is maintained across this intersection of elements that occur at the firewall.
    • In Canada, the firewall must be capable of sustaining a lateral load of 10.44 psf (0.5 kPa) being exerted against it (from either direction) for the duration of time that the wall is rated for (in the event that structure is under fire attack on either side of the wall).

    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® for firewall applications, please contact NUDURA® Corporation through your Distributor Representative.


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