Of course, our roof truss design calculator doesn’t provide a guaranteed calculation or price. This will be done with steel joints and a bridge, added to support the weight of the entire truss. As well, running an attic air duct system can be very difficult, if the roof trusses were not designed for that application. Our truss calculator computes the best dimensional method to connect the pieces of the truss. Roof Truss - Design 1 - 24' span, 2-web, with plywood gussets (Figure 1) Figure 1 - Roof truss - 24' span, 2-web, with plywood gussets Detailed information for a 2-web roof truss with a 24' span with plywood gussets. The primary disadvantage of roof trusses is that the attic space is not easily usable for storage or potential living space. As well, running an attic air duct system can be very difficult, if the roof trusses were not designed for that application. The primary disadvantage of roof trusses is that the attic space is not easily usable for storage or potential living space. The information provided here is not intended to replace truss drawings. A pitch truss with a sloping (or non-sloping) vertical interior ceiling detail. Connector plates are generally 16 gauge to 20 gauge depending on truss design requirements. Used on larger trusses and for creating a pitched ceiling or an extra vertical space. Secondly, roof trusses can span very large distances without the need for any center support. Our roof truss calculator can be used to aid you in the purchase of your trusses by determining the quantity of trusses and lineal feet required. The first is that they are factory built making them far less labor intensive than forming and installing a roof support system on site. There are two primary advantages of roof trusses.