What is Wash Out Pit?
Definition of Wash Out Pit in Construction
The top board at the peak of a roof. The rafters terminate against the ridge board unless the framing is designed to bear rafter against rafter with no ridge board. This type of framing is a specially designed rafter layout and requires precise and experienced erection. The use of a ridge board, eliminates the delicate balancing of a rafter to rafter install and reduces the potential for error or miscalculation. In many large glulam or timber framing the rafter to rafter bearing is accomplished due to the falsework and temporary structures built to support the rafters during erection. The need to precisely position the rafters and balance the load is not necessary if the entire structure is being held up with falsework. The ridge board, once the building is erected is a non structural entity due to the interactions of the rafters, the roof sheathing, etc. The entire assembly acts as a whole, allowing the shifting of weight or forces to be equalized throughout the structure. Ridge boards when used are normally installed by a temporary bracing system, prior to the rafter installation. The ridge board is accurately placed in position and rafters are installed sequentially down the ridge board. In most instances opposing rafters are installed, one on the left side of the structure, then the mating one on the right. In this fashion the balancing of loads and forces is equalized to eliminate shift or bending of the ridge board. The rafters are then fastened to the ridge board with either a specially designed bracket or clip made out of galvanized metal or simply toe nailed in from the side. The forces on the fasteners is minimum due to the opposing loads implied on the ridge beam by the opposing rafters as well as the structural stiffening of the entire structure once the roof sheathing is applied.