joist sistering common practice

Hello everybody,

I have a question in regards to wood joist sistering as a solution to allow removal of wood framing partitions in old buildings: is it common practice to use a same length lumber therefore providing new pocketing for the new joists or just using wall to wall length new joists (without new pocketing)?

Thank you very much in advance.


It’s common practice, or should be, to have someone who knows what he or she is doing do the calculations required to answer your question. Each case is different. It is possible that wall-to-wall sistering is acceptable, but it is equally possible that sistering joists to double the span will be grossly unacceptable. If one 2x8 spans 12 feet, a double 2x8 won’t span 24 feet. The best advice anyone can give is to have the structure designed properly by a qualified design professional.

Your question almost sounds like you are trying to remove a bearing wall and compensating it with sistered joist above.
First all, sistering a full length joist to replace a bearing wall might not be enough, it might possibly require a designed gluelam joist of adequate size to carry the load above.

In most cases, it’s a job for a professional. Look for a licensed contractor, who’s insured and bonded. Get three estimates in writing. And make sure you’re comparing apples to apples. The estimates should cover the same work. Once the job is done, you’ll have a floor that’s long-lasting and solid beneath your feet.

Hope this helps.

Marcel :slight_smile: :smiley:

The May issue of JLC had an article pertaining to this very subject. It should be noted that I offer this as informational only and do not endorse taking on a project of this magnitude by unqualified individuals.

I totally agree.

Remember, as home inspectors our job is, primarily, to take on any of the buyer’s liability.

In such a case, where should the liability lay?

On the guy who got paid to do the work.

If a contractor, just as his “rule of thumb”, does this kind of work, is he qualified to do so, and, more importantly, will he “back up” his work? Structural engineers KNOW the proper way to do this (backed up by calculations and experience) and are insured in case they mess up (and have the liability, therefore).

What happens if this “fix” messes up in 5 years? Who will pay for the mistake? This is the question a home inspector should ALWAYS ask themselves.

Never assume the liability of others.

Hope this helps;

I could not agree more with the above posts. Too many times people think that if they double or sister a board that it can span twice as far. Glue lam’s are a great product for remodeling as they can be installed a lot easier than steel beams, however consulting with an engineer/architect is the best route before moving forward.
Great point Will about the liability…can’t be stressed enough…