Thread: What can happen with roof over.

People ask about roofing over an existing board deck where the truss are not evenly spaced.
Roof had plywood installed over old boards. Rather than tear down to truss they attached to the deck boards. As a result the nailing has pulled up and the plywood ends have curled up. Not to mention that the roof shingles are puckered up. This was a case of hit and run roofing.

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No offense, but how can you be sure it wasn't unavoidable wind damage?

I see plywood or OSB over shiplap quite often, but it doesn't automatically cause failure like that.

I dont see any attic vents, if there are not any that could cause it

Originally Posted by MARVIN TOWNSEN

I dont see any attic vents, if there are not any that could cause it

There could be soffit and gable vents ...

wood shingles are torn off everyday and plywood put over the skip sheathing the wood shingles used to be nailed to. Now, if they did not break the plywood on the skip sheathing or poorly nailed it to the sheathing or loosened many a 1x ripping the shingles off and did not secure it nailed/screwed properly before putting the plywood on .... in other words just did a screwed up job then it will look like your roof in the end.

Done right there are never problems.

Never really thought about it but it seems like you would run the new plywood parallel to the original rafters in this application with the ends of the plywood breaking on the strips run perpendicular to the rafters.

Looks like that failing chimney chase will shortly take care of the rest of the undamaged roof covering.

Originally Posted by Bob Wisnewski

Looks like that failing chimney chase will shortly take care of the rest of the undamaged roof covering.

??? I must be missing something. What is it you see with the chimney Bob?

Nick,

From what I can make out from the photo, looks likes there are some missing bricks???

On the right-hand side? If that's the area, it looks like the straps that are securing the antannae to the chimney. Kind of hard to tell with the size of the pic but you might be right with some being a bit deteriorated behind the straps. The top one looks to be the most suspect.

Yes Nick, that is the area I was looking at. Sorry Garry, I know this was not the subject of your post.
Bob

There was a lot of things wrong with the roof.
Purpose of post is to just show a plywood roof over and why not to do it.
There are times that you may get away with it but still is a bad idea/practice.
General info, house 100 + yrs, no ventilation except for two windows, attic had finished ceiling.

Originally Posted by Garry Sorrells

There was a lot of things wrong with the roof.
Purpose of post is to just show a plywood roof over and why not to do it.
There are times that you may get away with it but still is a bad idea/practice.
General info, house 100 + yrs, no ventilation except for two windows, attic had finished ceiling.

I would argue that is the reason why you should do it properly

i see stains coming from chimney chase and somethnig strapped to chimney--not suppose to be.

chas

Originally Posted by Garry Sorrells

There was a lot of things wrong with the roof.
Purpose of post is to just show a plywood roof over and why not to do it.
There are times that you may get away with it but still is a bad idea/practice.
General info, house 100 + yrs, no ventilation except for two windows, attic had finished ceiling.

Instead of the rafters being X apart from one another you has the 1x closely spaced. If the 1Xs are nailed down well the plywood will be secured far greater than the entire 8 foot length of the sides touching only several 2x. As far as the ends the are very secure as well due to the close spacing of the 1X

Don't see how you can go wrong if all is secured properly. I think it actually tightens that roof up a whole lot more. It is similar to 1x3 strapping nailed to ceiling joists and then the drywall nailed to it. I believe the entire home tightens up more when done so.

Not a bad practice at all

Other than doing something wrong as in any installation of anything, If done right I just do not see why there would be any concern. Yours was simply done wrong or other problems arrose aftert the installation as is possible with any installation of anything.

Originally Posted by Ted Menelly

Instead of the rafters being X apart from one another you has the 1x closely spaced. If the 1Xs are nailed down well the plywood will be secured far greater than the entire 8 foot length of the sides touching only several 2x. As far as the ends the are very secure as well due to the close spacing of the 1X

Don't see how you can go wrong if all is secured properly. I think it actually tightens that roof up a whole lot more. It is similar to 1x3 strapping nailed to ceiling joists and then the drywall nailed to it. I believe the entire home tightens up more when done so.

Not a bad practice at all

Other than doing something wrong as in any installation of anything, If done right I just do not see why there would be any concern. Yours was simply done wrong or other problems arrose aftert the installation as is possible with any installation of anything.

I agree whole heartedly. I have a feeling improper venting played pretty big role also

It's my understanding that inadequate spacing between sheets of plywood can cause the plywood to buckle and that inadequate roof deck ventilation aggravates the condition.