how to measure joist spacing in attic w/o access

[mrobinson]

want to measure joist spacing in attic but there is no access what is the best way to approach?

[Steven Hockstein]

The best approach is to make an opening in a closet ceiling somewhere to see the framing. Add a removable cover. Access is a good thing (and required by code). It makes it a lot easier if you ever have a problem and need to get into the space.

[Marc]

If you can see some nail heads on the soffit panels, measure the distance between them along the long dimension of the panels. It usually agrees with the rafter spacing, since the lookouts (the 2X4 members that the soffit panels are nailed into) are parallel to the rafters and are generally secured to the rafter tails.

Marc

[Garry Sorrells]

What is wrong with a "stud finder" ?? Simple and effective.

Then there is the question of why the spacing is being questioned. [:-magnify

Unless the ceiling is layed up plaster or plaster over board a $10 stud finder will do the job.

Then you could take a strong magnet and find out where it will will hold to ceiling, that is a nail/screw. I have a gismo that is a magnet in a plastic box that does basically the same thing, magnet points to metal though its about 45 years old but it works (simple and stupid--KISS). PS- No batteries required and will work in the dark.

Then there is the thump the ceiling and the higher pitch is the stud. Drive a nail to verify then repeat and measure....

[John Kogel]

If you can borrow an IR camera, that works well for finding joists. But you got good answers above.

[mlparham]

Why does a stud finder always beep when I hold it to my chest? I am to humble to believe that I am as sturdy as a stud.

[Garry Sorrells]

Why does a stud finder always beep when I hold it to my chest? I am to humble to believe that I am as sturdy as a stud.

It recognizes something as dumb/dense as a 2x4. [:-monkeyd

Maybe different if you had held it somewhere else...[:-censore

[kurt]

HA! Maybe Morgan is anatomically discombobulated....

[Tom Raymond]

Just dense.

Sorry Morgan. That was just too easy.