roofing question

[jakeh]

I am remodeling an old corncrib/grainary to be my shop. It has wooden shingles and I want to put steel on. I have had some contractors tell me that they would lay purlins on the shingles and screw the steel to them, and have had others say that I need to remove the shingles first. What do you guys think?

 

[rlitman]

I would say that it depends on the condition of the wood, and how many layers you have up there already.

 

[jakeh]

Only one layer of shingles. Some of the roof boards have gotten wet, the 2x4 rafters all look good.

 

[Falcon67]

We've had a couple of houses with wood shingles under comp and every time we've taken it down to the purlins under the wood. I would expect the shingles to continue to deteriorate over time and if they do, you'll start to lose the support under the steel. That would be my fear, FWIW.

 

[rlitman]

We've had a couple of houses with wood shingles under comp and every time we've taken it down to the purlins under the wood. I would expect the shingles to continue to deteriorate over time and if they do, you'll start to lose the support under the steel. That would be my fear, FWIW.

If the shingles are under the steel, they'll be dry, so why would you expect them to deteriorate?

If they're already rotted, and not safe to walk on, then by all means, pull the shake down. The purlins underneath should already be adequate for hanging the steel, so you won't need new purlins (except any bad ones you need to replace). That may be enough time saved to make the demo worthwhile.

As for support under the steel, remember that the steel isn't being nailed to the shingles. It is being nailed to purlins that need to be nailed through to the rafters anyway.

 

[Falcon67]

I would expect them to deteriorate because they've already been in the weather for X years and they don't last forever. Which may well be off base. But for sure they would need to find the underlying purlins and strike lines across the roof, otherwise they are likely to miss the meat of the roof structure.

 

[bad_idea]

I say go up there one Saturday and yank the old stuff down and dispose of it, then have the roofers come in. Why take the chance of the old stuff causing you issues over saving yourself a day's labor? Please keep in mind I have no experience in the issue at hand, just expressing my general opinion. If it isn't too much of a hassle for me or a expense, I like to go the extra step to insure a quality product.

 

[Leaflessshadetree]

I'd remove the shingles to get ventilation under the steel. You don't want to trap moisture between the shingles and steel.

 

[jakeh]

Thanks for the replies. I had kind of decided to pull the shingles off, but it will be more than a Saturday job. It's a 12 12 pitch, so I'd need toe kicks to stay on the roof, and I'm an old fart with sore knees, and don't look forward to crawling around up there. Like bad idea says, why take the chance.

 

[rburke65]

What does your gut say? There ya go......now go and do it.

 

[bczygan]

Always remove the existing roof to install a new one. If for no other reason that to avoid the excess weight of material that is doing nothing for you..

 

[Stuart in MN]

I'd see how much the roofing company will charge to strip the old shingles. My 1913 house had the original wood shingles, with one layer of composite shingle over them, when I had the house re-roofed around 1990 (that was around 40 years lifespan for each layer, which wasn't too bad.) Anyway, the roofing company stripped it down to the bare boards and started fresh, and it took them no time at all to do the job (and I have a big house with steep roofs.) The point is, they'll probably have your roof stripped clean and the new metal roof done in a day; if you consider how much time and effort you'll have to put into doing it yourself, it's probably money well spent to have them do it all.

 

[TractorJeff]

Removing wood shingles takes more than a day.
Been there, Done that!
You need to be sure every piece of rusted old nails is removed!
I was **** about that and only had one that I missed, I felt a bump in the steel, pushed on it with my hand and poked a hole through the sheet!
I drove a roofing screw into the offender to prevent leakage.

 

[Tweeker]

Remove shingles for all the obvious reasons. Bummer I know.

 

[volleyball]

If it is shingled correctly, you will have boards with gaps. If the boards are thick enough, they can be your purlins. If it is plywood, then no.
I would remove the wood, not because of rot, as it will hold up a hundred years under a metal roof but more as a way to get the metal to lay flat.
As with most metal roofing jobs, I suggest some high density foam boards underneath. It will give you a flat surface and insulation. Actually you could leave the wood shingles, lay foam board on top, purlins on top of that screwed to the rafters and then metal on top of that. The cost of the foam will be saved by the cost of shake removal.

 

[Stuart in MN]

Removing wood shingles takes more than a day.

If you're doing it by yourself, yes. If a roofing company does it, they basically send an army up on your roof and the work goes fast.

 

[CraigStu]

just have the roofers remove the shingles. I know you have seen roof crews at work. They walk around up there like they were born there. I am also an old guy w/ sore knees and I think there are jobs I just shouldn't tackle any more.

 

[G McKay]

At first I thought you were talking about wood shingles on the side as siding. But I guess that you are talking about the roof. So, If it were me, then yes, I would probably remove the wood roof shingles. They'll make a nice bonfire for the kids. Or you might sell them as firewood?

 

[yeldogt]

Around me they put that heavy corrugated metal over cedar shakes all the time -- I think it is the standard barn roof fix. They lay down horizontal strips and shim the panels.

If it is a cedar roof -- when you take off the cedar you will not have any deck. The cedar roof becomes your roof deck.


The narrow panels that look like standing seam require a bit more care -- but I have seen them do this also.

They put metal roofs over asphalt shingles.

The old part of my barn is plywood with 3 tab shingles - the roof is a bit wavy. Every metal guy said to leave the old roof and shim on top -- or rip it all off and put new plywood down .. and still have to shim it since the old rafters will not be flat and true enough for a standing seam.

 

[CoyoteKyle]

I used to be a roofer. +1 on removing. If not they will cause problems in the long run. Plus those silverfish alien bugs love those cedar shakes and probably already infested.