Precision Board HDU high density urethane is used very effectively to make dimensional signage. Its long exterior life and ease of use makes it an ideal material. However, like all new state-of-the-art products there are certain precautions and considerations that must be taken to achieve the most they have to offer. This information will address the precautions and considerations for mounting and strengthening high density urethane signage.
Precision Board HDU high density urethane is comprised of millions of tiny cells. These cells are created during the chemical foaming reaction process and, for the most part, are separate from each other. This condition creates a closed cell structure which does not allow anything to absorb into it and results in long life expectancy.
Due to the cellular nature, high density urethane must be treated differently than wood. Unlike wood, Precision Board HDU has no grain, it cuts easier, sandblasts and routs faster and smoother, plus carves quicker with less effort and wear on the carver. This cell structure, however, requires special consideration when mounting and attaching the sign.
Following are some of the more common mounting conditions and recommendations:
Signs mounted directly to the building wall.
Flat mounting directly to the wall is best accomplished using studs as hangers. The first step is to put the studs into the wall. Concrete nails work well in masonry walls as do galvanized nails into wood walls. After the studs have been installed the sign should be leveled and pushed back onto the studs with enough force to cause a small locating indent at each stud. Be careful not to damage the sign. Using these indents for proper hole location, drill a hole about 2 times larger in diameter than the stud. Depth of hole to be about 1/4″ deeper than attachment. Fill the holes with silicone caulking and slide the sign over the studs. Verify sign is still square, support as necessary, and let cure overnight before disturbing. Leaving the heads on the studs allows the silicone to grip the sign and keep it from being pulled off the wall during high winds. The silicone maintains a strong yet flexible attachment that allows for any wall movement. This type of installation also keeps from having to drill and repair attachment holes through the sign face.
Do not attach a weight bearing screw or bolt directly into high density urethane. Because urethane has a cellular structure and doesn’t have grain, any weight bearing screw or bolt must have extra support around the threads. Hanging signs are typically hung from eye bolts that are either screwed directly into the sign or that are welded onto the supporting steel framework that is screwed into the periphery of the sign. Attaching eye bolts or weight bearing screws into urethane should be done by drilling a hole about 2 times larger in diameter than the shank of the screw and about 1/4″ deeper than length. Fill this hole with a structural 2 part epoxy, such as EP-76 and insert the eye almost flush with the surface. Excess epoxy can be smoothed around the eye with any suitable tool dipped in mineral spirits. The epoxy holds the threads of the fastener and greatly increases the holding surface around the inside of the hole. This makes the fastener able to take much more load and eliminates the loosening effects caused by expansion and contraction of the fastener.
Strengthening wide expanses of high density urethane
Because urethane does not have grain, it also has less beam strength than wood. Wide, unsupported, expanses need to take this into consideration. This situation can be addressed in several ways depending on the design of the sign and the unsupported expanses.
Three possibilities are:
1. Add a metal band around the periphery of the sign and attach it as mentioned above.
2. Add a metal extrusion in the shape of a T along the entire bottom edge of the sign. A slot is cut up into the bottom side of the sign that is a 1/4″ wider and deeper than the leg of the T. This slot is then filled with a strong, hard, two part epoxy, like EP-76, and the T inserted into it. The excess epoxy squeezed out of the slot welds the other two legs of the T to the bottom edge of the sign adding rigidity without any visual impact.
3. Bond urethane sheets to a center sheet of exterior grade plywood, Dibond or equivalent. Make sure that the bonding adhesive is waterproof (i.e. PB Bond 240 or PB Fast Set). Call us for bonding tips.