Applied Research -  Field Tests -  Above Ground Exposure

Lap Joint Exposure

Test Method: AWPA E16-98

The lap joint exposure test simulates the use of wood and wood based materials in exterior construction that may be exposed to the weather, but does not contact the ground. Some examples include decking, railings, and wall sheathing. Lap joint specimens are exposed horizontally in above-ground racks and inspected at specified intervals for decay and insect damage. Here (right side) is shown a lap-joint exposure rack full of specimens.
LAP JOINT INSPECTION Lap joint specimens consist of two overlapping parts joined together with a nylon bolt-spring-nut assembly to accommodate thickness swell. For inspection of the overlapping joint the two halves are pulled apart (see photo on the left).


Depletion Rate

Test Method: MTU Test Method

Depletion rate testing evaluates the persistence of the wood preservative in severe above-ground moisture exposures. Depletion rate specimens are positioned horizontally to maximize the severity of the test. At specified intervals a number of specimens are removed from the field and analyzed for preservative content to determine the rate of preservative depletion.


Termite Exposure Field Test

Test Method: MTU Test Method

The MTU Termite Exposure Test Site located near Honolulu, Hawaii USA provides a severe challenge because of its very high Coptotermes formosanus population. The termite exposure test evaluates the susceptibility of the treated wood, or wood composite to termite attack under conditions that may be damp, but where some protection from the weather is provided. Sill plates, framing, timbers and interior beams are examples of common construction areas under these conditions. Wood, or wood composite specimens are arranged on a low acrylic grid platform so that they are in contact with aspen feeder stakes, which in turn contact aspen bait stakes. The aspen bait stakes go through the acrylic grid to rest on a plywood base, which rests on the ground. The plywood acts as an additional food source to draw termites to the area. The specimens are examined and rated for termite damage at specified time intervals. The arranged termite specimens are covered with a treated wooden box to protect them from the weather. View a detailed drawing of a termite box.

Siding Exposure

Test Method: MTU Test

The siding exposure test evaluates decay, insect and weather resistance of coated composite panels under the most severe above-ground conditions. Siding specimens are mounted unto an exposure rack, which is positioned either vertically, or at a 45 angle to the ground. A 45-angle siding exposure rack is shown here. Maximum weathering is achieved using this orientation.
90 SIDING EXPOSURE RACK Here (left side) is shown a siding exposure rack set up at a 90 angle to the ground (vertical). This simulates siding exposure as typically oriented. As siding specimens are removed from the rack due to decay, or for analysis they are replaced with plain plywood.