What is the cost difference between trusses for asphalt shingles and trusses for concrete tiles?

Q: I am working on a research project at BCIT and was hoping you could provide me a ball park costing number for roofs going from asphalt shingles to concrete tiles. Costs increases in both the material and time to design per square foot or meter would be ideal.

A: This is a great question that I bet a lot of people would like to see an answer to. Because of the difference in weight of the various roofing materials, there is definitely a difference in truss cost as well.

There are a couple of factors that increase the cost of the trusses and the first one is mainly the additional dead load. With the extra loading the distance between webs (panels) must be decreased and the size of the connector plates increases too. Lumber species and grades all go up too. These all add to the cost. Another item to consider is long term deflection of the panels in the truss. Though a 2×4 top chord is capable of supporting the additional dead load imposed by the concrete tiles, the effect of this heavy roofing material can tend to bow the top chords down between web joints over time – long term deflection. A solution is to shorten up the panel lengths or perhaps go to a 2×6 top chord. Both methods have an effect on cost and design time.

Depending on the clear span of the trusses, the snow load, the roof slope and the truss configuration, the additional weight may have little effect or it may significantly increase the truss price.

So, with all that said and assuming that you are talking about concrete tiles – which may add as much as 15 pounds per square foot to the roof – I would say from past experience that on an average, a concrete tile roof could cost as much as 15% more than a conventional shingle roof.

I hope this answers your question but should you require more information or answers to other questions, please feel free to contact me.

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