Old House Question
Old House Question
(OP)
Example Scenario: House is 100+ years old, wood framed, raised floor with crawlspace & pier supported. Engineer A is asked to size a beam for a interior load bearing wall that will be removed for renovations. Engineer A determines loads, sizes beam, and makes modifications to foundation under new beam supports. Engineer A also had a quick look at the structure as a whole and did not see any obvious signs of structural damage or safety concerns.
Engineer B at the city determines that the 100+ year old floor joists, roof rafters, and header beams are not correctly "sized" according to loads from current codes and a free structural software he downloaded online. No work or alterations are planned to be made on these components. Engineer B at the city requests full calculations on these components to determine structural adequacy.
Engineer A runs calculations on these additional components and determines some are adequate but others are inadequate by about 5 to 15%. What would be the best option for Engineer A in this situation?
A) Make an arguments with Engineer B at the city that the new work will not affect the components in question.
B) Ask Engineer B for his calculations to determine any differences from yours.
C)Tell the contractor that he needs to do alot more work and probably lose a client.
D) A & B
E)Do what your told and dont question the authorities :)
Engineer B at the city determines that the 100+ year old floor joists, roof rafters, and header beams are not correctly "sized" according to loads from current codes and a free structural software he downloaded online. No work or alterations are planned to be made on these components. Engineer B at the city requests full calculations on these components to determine structural adequacy.
Engineer A runs calculations on these additional components and determines some are adequate but others are inadequate by about 5 to 15%. What would be the best option for Engineer A in this situation?
A) Make an arguments with Engineer B at the city that the new work will not affect the components in question.
B) Ask Engineer B for his calculations to determine any differences from yours.
C)Tell the contractor that he needs to do alot more work and probably lose a client.
D) A & B
E)Do what your told and dont question the authorities :)






RE: Old House Question
Are you using lumber values from the era it was constructed? That lumber is generally quite a bit stronger than the numbers available now. Especially if you're just using software.
RE: Old House Question
Some say you only have to verify what you change. Some say you have to verify everything if you change anything. Some allow no evaluation if demand/capacity ratio is increased by <X%.
Find the section in your local code that deals with new loads on existing elements. Depending on what that says, pick one of your options.
RE: Old House Question
RE: Old House Question
RE: Old House Question
As Jayrod said, the lumber back then was super strong and most problems are only serviceability related.
RE: Old House Question
Mike McCann, PE, SE (WA)
RE: Old House Question
In my situation, my house is over 150 years old. Small log timber roof rafters and 2 ft (or more) width lumber sheathing (random spacing, random and tapering diameter). I ran the numbers a few years ago and 'by Code', it is about 250% overstressed. I have seen it with 3 ft. of snow. Other than a bit of a sag, it stood the test of time before I ever purchased the house and continues to perform satisfactorily. I am not worried and have no plans to modify anytime soon.
RE: Old House Question
My own house was built in the 1860's. The underside of the roof rafters are still covered with newspapers from the early 1860's, used to cover the gaps in the sarking boards = draught excluders.
By any stretch of the imagination it looks dubious structurally, but it is still here. I'm sure the numbers would say it fell down years ago.
RE: Old House Question
Engineer B is being an arse.
Plus F - Actually read the building code relevant to your area and then tell Engineer B where to find the relevant section which he clearly hasn't bothered to find it.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Old House Question
Engineer B can't just make you do whatever he wants. He has to have justifications for his actions. Is he citing any documents?
Sounds like a level 2 alteration per the International Existing Building Code 2012.
In section 807.3 it states: "The minimum design loads on existing elements of a structure that do not support additional loads as a result of an alternation shall be the loads applicable at the time the building was constructed"
RE: Old House Question
If you'd rather argue about it so as to not set the precedent of having to submit calculations for any whim of the building official, you may have to dig into Florida Existing Building Code, too:
2017 Florida Building Code - Existing Building
The code grants the official broad authority, however
401.2.1 Existing materials.
Materials already in use in a building in compliance with requirements or approvals in
effect at the time of their erection or installation shall be permitted to remain in use
unless determined by the building official to be unsafe
RE: Old House Question
We typically default to a Douglas Fir Use Book published in 1958.
RE: Old House Question
It varies based on lumber type, but in general it is pretty east to justify #1 or Select structural strength from today's code.
The national parks service also has a document and tool for field grading and analyzing historic lumber that I have found useful. If the building official holds you to today's lumber strength, you may be able to field grade the joists to #1 or SS.
https://www.ncptt.nps.gov/blog/a-grading-protocol-...
Both of these routes give you a little more to lean on than just "wood used to be stronger, trust me"
RE: Old House Question
RE: Old House Question
TTFN (ta ta for now)
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RE: Old House Question
RE: Old House Question
Dik
RE: Old House Question
My point really was that the Engineer should not be eating it. If the engineer's contract is with the contractor then the contractor should pay him and get reimbursed accordingly.
RE: Old House Question
J.K! Contractor will get it and probably pass it to the owner.