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Frequently Asked Questions - ARXX
Frequently Asked Questions on Arxx Walls and Foundations
and the installation of the High Performance Wallsystem:
Q: Do I need an engineer to review
my building plans?
A: In 2006, Ontario included ICF construction in Part 9 of
the Building Code. However, due to the high seismic activity
in Eastern Ontario, an engineering review is required for
all above-grade walls.
Q: Does it matter what side is up
when installing the Arxx forms?
A: Arxx forms have a definite top and bottom. All Arxx forms
should be installed so that the diamonds are facing up and
the sockets are directed down.
Q: Does expanded polystyrene (EPS)
present a serious fire hazard?
A: Expanded polystyrene will burn if exposed to a large enough
heat source. There are many products in the home that will
ignite at a lower temperature than EPS. The EPS in an Arxx
forms has a flame retardant additive incorporated during the
manufacturing. EPS will melt when exposed to temperatures
of 300 F to 500 F. If additional heat is applied and an ignition
source persists, the molten styrene may ignite at temperatures
over 600 F. (Note the flash ignition point for fir plywood
products is approx. 500 F).
Q: Is burning EPS toxic.
A: Test reports conducted by the National Research Council
state: "The maximum toxicity index obtained from the
combustion of polystyrene was of the same order as that of
Q: Does EPS "off gas".
A: EPS in the Arxx forms does not and never has contained
any CFC nor HCFC products. The forms are made by a steam process
that utilizes "pentene gas" as a blowing agent.
The type pentene dissipates from the product within 48 hours
of manufacturing. By the time the product is used in construction
there would only be trace amounts left in the EPS.
Q: Are there different types of
A: EPS is listed, basically, under 4 property classifications-
Type 1,2,3, & 4. The characteristics are generally based
on the density. The density of the EPS defines the type. Arxx
forms are Type 2 EPS with a density of 1.5 pounds per cubic
Q: Can I leave Arxx forms exposed
to ultraviolet rays for extended periods of time (1 to 3 months)?
A: Yes, but you will notice a light dusting on the surface
and a discoloration of the forms. This does not indicate any
detrimental effects to the wall forms. We do recommend that
if the exterior finish will not be installed within a 3 month
period the forms be protected from UV rays by installing a
temporary building wrap type material.
Q: Can you vibrate or consolidate
the concrete in ICFs?
A: Arxx recommends consolidation with a pencil vibrator,
quickly in and quickly out.
Q: Do ICFs promote mold growth?
A: EPS is an inert, organic material. It provides no nutritive
value to plants, animals or micro-organisms. It will not rot
and is highly resistant to mildew.
Q: Do I have to finish my basement
walls with drywall?
A: All building codes in Canada and the US state that plastic
insulation (EPS) must be covered by a thermal barrier equivalent
to 15 minutes. This is achieved with ½" gypsum
board or an equivalent. Yes, all interior walls in habital
space must be covered with a minimum of ½" drywall.
Q: Why is the concrete poured in
3 foot (1m) lifts?
A: To alleviate the hydrostatic pressure from the concrete,
the first 3' of concrete is allowed to set for approximately
1 hour before the next 3' is installed. This is achieved by
installing the concrete for 3' all around the perimeter of
the project, then go around again, on top of the previous
pour, for another 3' and so on until you reach to desired
Q: Is there a problem when placing
concrete, dropping concrete from the top of the wall which
may be over 9' ?
A: No. The specification in the America Concrete Institute
(ACI) do not limit the maximum distance concrete can free
fall. Engineering studies and reports have shown that free
fall from up to 35' doesn't reduce concrete quality and there
is no evidence of segregation or weakened concrete.
Q: Can you build your Wallsystem
in cold weather?
A: Yes, the forms actually insulate the concrete and enhance
the curing process. The top of the forms need to be covered
so exposed concrete does not freeze.
Q: When can I backfill the foundation
A: The concrete must cure for a minimum of 7 days and the
foundation wall must be laterally supported, meaning the first
floor is installed. All below grade waterproofing/dampproofing
must be installed.
Q: What are "blow-outs"
A: A "blow-out" is a break in the form, generally
due to the pressure from the concrete during the pour. A pre-
pour review of the wall system, installing additional strapping
and support will prevent blow-outs. In an Arxx form, generally
the size of a blow-out may be 6" wide by 16.75' high.
If a blow-out occurs, the concrete pour moves to another area
on the wall, the hole is patched and the pour resumes.
Q: How do you control voids in the
A: The concrete mix is a high slump that means the concrete
flows easily. The person in charge of the pour should watch
the concrete flow evenly throughout the whole wall to ensure
there are not void pockets. Arxx also recommends vibrating
or consolidation that will enhance the concrete flow.
Q: Can I install a 16' garage door
and/or large windows in a concrete wall?
A: Yes, the Arxx prescriptive code has detailed lintel designs
for large openings up to 16'-4". Larger openings will
require an engineered design.
Q: What do termites do to the foam?
A: EPS is an inorganic material and is not a food source