So, I have been doing research into the use of Insulated Composite Concrete Forms (ICCFs) for small-scale construction, and that has led me to looking at the Rastra ICCF system, as it has been in production for a long time, is relatively well documented, and is versatile enough to answer a variety of building design needs; in particular, Rastra parts can not only be used to build walls, but horizontal assemblies (floors/ceilings/roofs) as well.

However, the published documentation for Rastra ICCFs stops short of providing span charts for their use in horizontal assembly construction. I contacted Rastra's technical support regarding this omission, and they sent me a PDF file that included the following drawing and determination-table (span chart) for Rastra floor systems using Trigon-type reinforcing girders and supplemental reinforcement laid in a bed of Rastra end elements, then finished with a concrete pour:

drawing of Rastra floor using end elements

Rastra floor span table

Most of this is clear enough (although I'm not sure how to get my paws on prefabricated reinforcing girders of the style they used, given that I'm across the pond from them); however, it does not answer one question for me: are the loads given across the top of the posted table inclusive or exclusive of the floor assembly's unit weight (inherent deadload)?


1 Answer 1


The load values in the table is described as the design load with no further qualifiers and that will generally mean the total load including all dead load and live load as well as safety factors.

It would usually be problematic to specify the capacity exclusive of the inherent dead load because multiple load safety factors need to be checked, that is both a set of factors with high safety on live load combined with lower safety on dead load as well as a high safety on dead load combined with a lower safety on live load, so the critical safety factor on the inherent dead load would depend on the size of the live load and non-inherent dead load.

Since you write that you're across the pond from the manufactorer, I'll add just for good measure that since material safety factors etc. vary from country to country, such a table is only valid for the jurisdiction it was intended to be used in.

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    $\begingroup$ Something which also points to this being the sum of inherent dead load and other loads is the fact that at a load of 4, no additional reinforcement is needed. This makes sense if that's taken as an additional load of only 0.5 above the inherent 3.5 (so the minimal reinforcement is only slightly excessive for the inherent load). The opposite case (where the loads are exclusive of the floor weight) would mean the minimal reinforcement is obscenely high for that base case. $\endgroup$
    – Wasabi
    Jan 25, 2020 at 19:49

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