Quote:
Originally Posted by RcCalais
There is DIY and many contractors that can install. My input is concerning the width of the stair. Some contractors will install narrow stairs that fit in without modification of the roof truss. This causes problems in getting things through the opening. It is well worth a little extra cost to add a couple of headers to get a larger width.
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Trusses are constructed to specific structural designs that have been approved by Structural Engineers. If you modify your truss you need to submit approved revision plans to the local authorities for their approval and acceptance. If you modify trusses without approval, your house is no longer built to its approved design. If there is a storm with consequent roof damage, etc. your house insurer may decline your claim since you made unapproved structural changes to your house.
If you want to consider any truss modifications, request that the installer/contractor has an approved structural design and has the approval of the local building inspection organization for your specific house. Alternatively, your contractor may have the design as an approved standard covering similar truss designs including all truss and modification connections prepared by a licensed structural engineering company and provided by the stairs company.
It has been 60 years since I studied truss design. Modifying the bottom chord to make a wider opening seems to make it very difficult to maintain the bottom chord's ability to sustain tension loads in normal situation and compression in wind caused uplift unless the attic floor had specific fastener (screws) patterns and sizes as specified by the structural engineer.
If you have questions, talk to the local building inspection organization.