Victoria cottage - increasing bedroom addition length

[NavyDave]

I'm going to be building my foundation in the next couple weeks and have a quick question about pier spacing for the bedroom addition. I am planning on increasing the length of the bedroom from 14 feet to 16 feet. Would there be an additional pier needed under each side bedroom beam or is the single mid pier sufficient for 16 feet? With 8" sonotubes this should leave a distance of 7' 4" of unsupported beam. Is this ok?

Also if it matters, my bedroom addition will only be a single story and not full plan height as the plans show.

[John Raabe]

I can't really answer engineering questions on the forum. Too many variables. For instance, are you doing a ridge beam through here or trusses? What is the snow load? Those are two big contributors but there can be others. If for instance you replace the ridge beam with trusses or rafters with a rafter tie it doubles the roof load on the side beams. If that is the case you should add the extra pier and cut down the beam spans. Best to have someone check these beams for the new conditions.

[NavyDave]

My plan is to go with the easier to build and less expensive rafters and rafter tie build since i'll be a semi solo builder.  My snow load is estimated to be only 10 PSF which is quite a bit less than average and I have a very solid bedrock footing. I will be double checking with a local builder for piece of mind but will also be adding the extra pier on each side as you suggested.

Also i'm planning on adding a single additional pier in the middle of the main 16' x 28' structure where the double floor joist spans the 16 feet. It just seems like that's where the majority of the weight is (hence the double joist). To me though, piece of mind makes it easier to sleep at night.

[John Raabe]

I think your analysis is good. I also think your addition of a pier in the mid-span of the double joist is a good idea and I will add that on the next update.