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Frequently Asked Questions


Deficient SFRM Density/Increase Thickness

 

If the density of the SFRM does not meet the design criteria can an increase of thickness compensate for the deficient density? If the preceding is possible, what responsibility or duties does the Special Inspector or the agency/laboratory have?


When determining the density of SFRM the Special Inspector is referred to ASTM E605 Standard Test Method for Thickness and Density of Sprayed Fire-Resistive Materials (SFRM) Applied to Structural Members. Section 8.4.1.2 states that when the calculated average density of the SFRM is less than that allowed by the respective fire resistance design see Note 4 & 5. And Note 4 states the following: “A thickness to density correction formula is contained in certain fire resistance rating criteria or is available from some SFRM manufacturers. Consult the rating criteria….before citing for deficiency.” In some cases it has been determined that an increase in thickness will compensate for the deficient density, so what duty does the special inspector/agency/laboratory have in such a case? If we go back to the IBC 1704.10.4 the laboratory is to determine the density according to E605. It makes no reference to Note 4 in using a correction formula. 1704.10.4 states, “The density of the sprayed fire-resistant material shall not be less than the density specified in the approved fire-resistant design.” Unless the fire-resistant design mentions a correction formula and the design professional performs this calculation, the as-measured low density is a non-compliance. From the point of view of the special inspector /agency/laboratory it should be reported in a timely manner to the contractor as a discrepancy for correction. 

The concept of a correction formula has a valid basis and should not be considered as a loop hole or an easy way out. It is based on the same design concept of the original tested assembly but it is up to the design professional to determine if the increase in thickness compensates for the low density of the SFRM. As special inspectors or agency/laboratory we report our findings, and the interpretation and revisions are at the discretion and approval of others.

It would be appropriate to mention the alternate method for determining the in-place density stated, in ASTM E605 Section 8.3 as a referee method. This method measures the volume of the material without the need for thickness or area measurements. It can be used to retest a sample that may be in question.  It reduces some of the measuring and sampling variables that are inherent with other methods.

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How Many Thickness Measurements for SFRM on Fluted Deck?

 


 When measuring thickness of SFRM on fluted decks IBC 1704.10.3.1 now references ASTM E605, while in the past we have used Technical Manual 12A. While the wording in the manual seemed confusing, an appendix clarified that 12 thickness measurements should be taken. Upon reading E605 it seems to indicate that we should “take four random symmetrical measurements”. With such a significant discrepancy between the two can you explain the right procedure?

  

The new IBC replaces the Technical Manual 12A, Standard Practice for the Testing and Inspection of Field Applied Sprayed Fire-Resistive Materials  with ASTM E605 as a reference standard. However the user should be cautious as to the extent of the reference. The IBC uses E605 for thickness determination but has wording that supersedes E605 on the rate of testing. E605 conducts thickness testing at a Rate of one bay per floor or one bay for each 10,000 sq. ft., whichever provides the greater number of tests. On the other hand, IBC 1704.10.3.1 would have the inspector take the average of "not less than four measurements for each 1000 sq. ft. of sprayed area on each floor or part thereof". With such a conflict we refer to IBC 102.4 “Where differences occur between provisions of this code and referenced codes and standards, the provisions of this code shall apply”. So, when writing an SOP for performing thickness determination the following could be adopted: 

“Layout a 12 inch square every 1000 square ft of sprayed floor area and take four random symmetrical measurements within that square, one each of the following: valley, crest, and sides, and report as an average”.

NOTE: This change has drastically increased the amount of testing on fluted decks.


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Frequency of Testing Thickness for SFRM

 

IBC 1704.10.3.1 references ASTM E605 for thickness testing and E605 uses a frequency of testing, “at one bay or 10,000 sq. ft of floor area” but 1704.10.3.1 calls for four test on floor decking per 1000 sq. ft. and 25 % of the other protected elements per floor. Is this a contradiction and which frequency should be used?

The IBC uses E605 for thickness determination but has wording that supersedes E605 on the rate of testing. E605 conducts thickness testing at a rate of one bay per floor or one bay for each 10,000 sq. ft., whichever provides the greater number of tests. On the other hand, IBC 1704.10.3.1 would have the inspector take the average of "not less than four measurements for each 1000 sq. ft. of sprayed area for floor decking and 25% of the other protected elements per floor. With such a conflict we refer to IBC 102.4 “Where differences occur between provisions of this code and referenced codes and standards, the provisions of this code shall apply”. A sample Operating Procedure follows:

FLOOR, ROOF AND WALLS

Sprayed fire-resistive material (SFRM) thickness, applied to the listed members shall be determined in accordance with ASTM E605. 

For every 1000 sq. ft. of SFRM applied, four measurements shall be taken in accordance with ASTM E605 and averaged for determination of the thickness.

NOTE:  The number of tests per square footage differs from ASTM E605.

STRUCTURAL FRAMING 

Thickness shall be determined on 25% of the members on each floor in accordance with ASTM E605.

NOTE:  The number of tests per floor may differ from ASTM E605.

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Adhesion/Cohesion of SFRM

                                                (Bond Strength of Fireproofing)


During a recent project we found the Sprayed Fire-Resistive Material applied to the steel substrate to sound hollow upon surface tapping. The project specifications call ASTM E-736 Cohesion/Adhesion of Sprayed Fire-Resistive Material Applied to Structural Members as controlling the required bond strength. The old UBC Standard 7-6 and ASTM E-736 do not specify whether to cut to the substrate or not. My question is after setting the cap with epoxy and letting it set for approximately 24 hours are we to cut around the cap to the substrate or are we to test it in-place without cutting around the cap?.

  

  

 The intent of ASTM Subcommittee E06.21 when writing E-736 was to outline a standard method to measure the combined bond strength from cohesion and adhesion of SFRM when applied to a structural member. Cutting around the cap down to the substrate will isolate the bond strength to only adhesion and may there by indicate why your project sounds hollow but would not be a standard method to substantiate an unacceptable application of SRFM.

Since you suspect an improper application, it would be prudent to test the SFRM in the standard method and to also cut around the cap and test just for adhesiveness and report the findings to the design professional.

www.Wordnet.Princeton.edu/perl/webwn defines cohesion as the intermolecular force that holds together the molecules in a solid or liquid. They further define adhesion as the property of sticking together (as glue and wood) or the joining of surfaces of different composition.

 

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Clarification ASTM E605 SFRM Density

 

 

 A fireproofing contractor contends that when measuring SFRM thickness on a density sample, the minimum maximum of 25%-1/4 inch rule (ASTM Section 8.1.2.1) applies when averaging the 12-thickness measurements. As a laboratory we believe the measurements should be actual not allowables.

 

You are correct, the averaging calculations for thickness measurements as mentioned in ASTM E605 section 8.1.2.1 do not apply when measuring thickness for a density sample. Section 8.1 of E605 specifies how to correctly measure the thickness of SFRM for the purpose of determining the average thickness, and areas of excessive thickness are dealt with in section 8.1.2.1. By limiting the measured thickness to a maximum of ¼′" over the design thickness, uneven application will not significantly skew the average thickness calculation to a "false high" reading. When measuring density, IBC 2006 refers us to section 8.2 of E605. Section 8.2.3 deals with thickness measurements for determining density, and quizzically refers to section 7.1, which has no practical meaning on thickness measurement. However, this section does note that 12 thickness measurements are to be taken, and no statement is made regarding adjusting the average of the 12 measurements. 

 From a practical viewpoint, the use of actual measurements for density calculations prevents "false high" density calculations. For a given weight of SFRM, a limited average thickness/lower volume (as determined by section 8.1.2.1) would generate an erroneous higher density than the actual higher thickness/higher volume measurements would. Thickness measurements are concerned with the application of the SFRM, while the density measurements pertain to the product itself.

 For SFRM to provide the required level of protection both the minimum average thickness and the density requirements must be met.  “Understating” the average thickness by disregarding a false high point does not result in an understatement of protection.  However, if we use thicknesses as determined by a maximum of the design thickness +1/4” (as used for average thickness determination) and not the actual thickness, we would be overstating the density.  This would result in an overstatement of the protection level, which must be avoided. 

 When this question was asked of Luke Woods of W.R. Grace & Co. – Conn. He stated the following:

 “The density test in Section 8.2 states that the thickness of the sample shall be determined by averaging the thickness of 12 measurements. I do not believe the 25% - ¼ inch allowance is applicable to these measurements. Also I would encourage you and your team to use the displacement method for determining density, Section 8.3.”

 It’s very appropriate to mention the alternate displacement method for determining the in-place density stated, in ASTM E605 Section 8.3 as a referee method. This method measures the volume of the material without the need for thickness or area measurements. It can be used to retest a sample that may be in question.  It reduces some of the measuring and sampling variables that are inherent with other methods.

 

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