One of them circled around the house, I have no clue how it did that but if that's on the ground level I'd assume it could be further above. I have some window well covers that are blowing off. I could put that savings in the market, an extra mortgage payment etc If I can get more power generated and lower my electric bill that would be great. So far it's pretty cool (no pun intended). I don't live in a historical district and frankly I don't get much for sun actually in the house. My main cringe would be defacing its roof with panels.Įh. Collar ties are used to connect opposing rafters in order to resist the ridge uplift cased by wind loads. A 1900s house is much more likely to be over engineered than a new one and capable of handling the additional load. As for the weight of a solar panel? it is minimal compared to wind loads and snow loads. If they are solid, the form will resist most anything.Ĭreating a truss or cripple that halves the rafter length, loadwise, is quite good, but generally adds to the load on any central load bearing wall, unless properly designed. The key to strength in any triangle is the strength of the junctions at the apexes. Since the triangle is stable, the effective length of the rafter(s) is only the distance from the birds mouth to the collar tie, making a rafter of small dimensions have the strength of one that is much more robust. Downward load at the apex of the roof would transfer equally to both bottom corners of the triangle. The failure point would be the section of the rafter outside of the triangular shape. Pressure on the collar tie going sideways will want to push the entire rafter and tie, and the rafter on the other side of the "roof." Pressure downward at that point will pull at the tie, trying to make it longer, which then will then instead pull the junction at the other end of the tie inward, which is resisted by the rafter on the other side of the roof. Imagine a roof section made of toothpicks glued together, and then a finger pressing in various ways against the construction. Primarily, a collar tie works as a response to wind load.Ī collar tie DOES create a limited resistance to downward loads. Deflection of one side of a triangle is minimized, and since a side cannot change in length, it creates a stable form. A chord is a geometric term, or one used in music to denote relationships between notes.Ī collar tie creates a triangle. Your best bet would be to get all of the specifications/weight on the panels and then have a engineer review the existing conditions to determine if additional framing work will be necessary.Ĭhord, not cord. If it is necessary to strengthen the rafters, you would need to add to the ceiling joists and then add cords or a cord at center span of each rafter which would dramatically shorten the span of the existing rafters adding to their strength. Collar ties do add to the resistance of the rafters and walls laterally (to spread) as mentioned above, so they basically are not necessary since the ceiling joists provide the same function.
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