“How to Perform Roof Inspections” Course

This open, public forum thread is dedicated exclusively for those students currently enrolled in InterNACHI’s free, online How to Perform Roof Inspections Course.

In this thread, students may:

  • review other students’ essays and images;
  • post their own essays and images;
  • ask questions and make comments; and
  • join in the conversation with other students.

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I actually just finished the video version of performing roof inspections. I was not clear on sheathing installation. Is it ok to install sheathing over barn boards and not have the ends meet at a rafter to be fastened just randomly nailing to the boards themselves?
Thanks, Bob

Just my opinion;

Because barns were built with less than exact measurements, finding 16", or 24", or even 32" centers across the entire roof, could be difficult. If the underlying boards present a fairly flat plane, and are in sound condition, then screwing the plywood to them shouldn’t be a problem.

However, that begs the question. If the underlying boards are sound, why the plywood? Are you about to put on a new roof material, that requires plywood underlayment, such as shingles?

If so, then look at the framing of the barn roof. It probably had steel over the boards, which were attached to some kind of rough-sawn truss. The new shingle roof will weigh considerably more. On the other hand, if the barn is old and is out of square due to wind from over the years, a layer of plywood on the roof could give the whole structure new found rigidity. Set up some instruments and assess the whole structure for level and squareness. Straighten it up and then re-enforce the roof. Re-fasten the sheathing boards to either the old/new rafters and re-sheath the roof with plywood. Then install whatever roof covering you were intending on using. Think about the fact that the structure is now more top heavy than before. Additional lateral bracing in the walls is likely required.

Lastly, I’m not Dknudson, I’m a student of his using his login and password. I have about 30 years experience as a general contractor in Canada, the US, and Central America.

Regarding bricks;
Years ago I conversed with a brick layer in Canada. (Freezing climate). He pointed out some houses that had crystals of ice stuck to the bricks. He said this was because some types of bricks have a top and bottom. Some bricks are cut to size, and the saw blade leaves tiny striations that can either face down, to drain (correct placement) or up, in which case they collect rainwater, rather than shed it. Then, if perverse weather conditions occur, the water freezes and prematurely damages the bricks.
In your section on chimneys and bricks, you talk about ‘spalling’. I think that this is the case, sometimes.
The solution obviously, is for the brick layer, to carefully choose which way is up/down, on each brick. Almost always, the bricks come on a pallet properly oriented. So, when getting them up to the scaffold, use a system that maintains that orientation.

I’m not actually dknudson, but a student using his login ID to study the course material.

Robert Pollock


I see a lot of chimney flashing that is just glued to the vertical surface with roofer’s caulk. Is this ever an acceptable practice, or is this always a defect that should be noted?

Roofing Inspection Course is next.

Getting ready to get started on the “How to perform roof inspections” course!
Moving right along!

For roof inspections, we have an amazing tool. Check out the SpectoScope at http://www.inspectoroutlet.com/spectoscope.aspx

starting course



Ready to begin this course. Electrical took longer that I expected with family matters taking time. Up and away. Lee

Ready to begin

Doing my revised course curriculum, in a progression corresponding with the Res SOP. Time to begin!

Starting course now.

Another one in the bag…

An informative course.

Just getting into this course, and am very pleased by the amount of information given.
I have a question though, regarding roof ridge and rafter pressures. Quiz #3 states that ridge and rafters are under compression, and seems to me that the proper answer to the statement should be that they are under deflection. What am I missing here?:shock:

Hi, Ken.

You’re correct. The quiz question has been changed. And I’ll be adding some content to the course in the next few weeks about conventional roof framing, trusses, compression, tension and loads.

Thanks for the question.