Installing a Metal Roof on a Building

I have a 20 x 40 shop building for my tractors. It currently has the original roof which is 2x6 rafters, some 1" x 12" boards for sheeting and then old cedar shakes. I am planning to install ribbed steel panels over the top. I was going to line the roof every 3 -4" with 2x4s for nailer boards for the tin. I was planning to nail/screw the 2x4s to the roof rafters and then screw the tin in the flats into the 2x4s. I am looking for some input on the ridge cap and the eaves. Should I use just standard steel ridge cap with the form enclosure strips for the gaps between the ribs? Or is the there a better option? Right now the eaves are just the ends of the rafters with no fascia board. Do I need a fascia board and some metal trim installed there or not? How far should I hang the tin sheets past the existing cedar shingles? Planning to do this weekend and want to do it right and not spend a ton of money (I know those two don"t go together!) Any advice, tips is greatly appreciated.

If the 1x12 are in good shape why add the 2x4.

All the older buildings on this farm had cedar shinges with 1x under them.In 1950's the shingles were covered with tin and it's still there today with no new perlins.

Hang the steel about 1/2 inch below the end of the shingles. Put rake and corner trim on the ends. Just screw the down side to the rafter.

Foam closers under the ridge cap keep rain from blowing under the cap and are sufficant.

Gary

i would definitely remove the cedar shakes. they are a serious fire hazard.

Ain't burned in the last 60 years, why would they burn with metal over them.

The rafters are in great shape (building was built in the 1960s) and they look new still. The cedar shakes have some small holes and has been leaking so I thought the 1x12s might be questionable. Definitely planning to use rake and corner on the end walls but I have seem some guys use it installed first at the eaves and then tin over top?

Our son put steel roofing on his shop with the rubber washered screws. After about 20 years the rubber washers have dried up & now he has leaks around the screws.

Vern

The washers are maid out of neoprene now don't know how long they last.Twenty-five years ago I put a dab of caulking on each screw on a roof of leaking around the screws and the roof is still holding.

I've done several metal roofs. I would not use 2x4's, the wood is too soft and the screws will not hold well. Use 1x4's. Much tougher wood.

I assume you meant to put your purlins on a 3 to 4 FOOT spacing, not 3 to 4 INCHES. (ytmag sometimes changes single quotes to double quotes.)

FBH, that makes no sense. Post frame buildings normally use 2x4s for girts and purlins. You're saying that 2x4s are OK for girts, but not purlins? That a 1-1/2 inch long screw drilled into 3/4 inches of pine is stronger than the same screw drilled into an inch and a half of pine? Unless your one inch lumber is made of much better stuff than your two inch, thicker is always better. Now if you are comparing 1 inch Douglas fir with 2 inch white pine, that's another thing, but you didn't say that. My experience has been that the quality of one inch lumber is usually pretty poor.

Let's not forget that a 1x4 can support very little weight, meaning that you're depending on the original roofing (if any) to support your snow load.

Could the fact that 1x4s are cheaper than 2x4s have factored into your thinking?

You are on the right track. I had it done and they put the 2x4's on 2' centers. I would maybe use a vented ridge cap and cover the eves and gable ends to keep driven rain and bugs out.

North side of my barn was done in 1975 with nails on the ribs,no leaks.I see screws in the flats now and expect there will be leaks if the washers fail.

I did the same job on my barn back in the spring. I left the old shingles on it going over them with 2x4's every 2 foot OC. If you go 3-4' the live load factor won't be enough to support snow and ice loads. Go to the roofing company website for installation directions and what they recommend for purlin spacing.

If you use screws like I did, they go in the "valley" or flat of the panel (opposite nails which go on the ridges). I also chaulked the overlap between panels.

bob

Did you ever notice how fast things get off track here. Ia Gary's got it right. Been contracting for 25 yrs and grew up as a farm kid. There's more than one way to skin a cat. If you are over laying your purlins there is really no need to go 2x4 if your existing substraight is good. Space those at 2' centers or less if you like. More will promote kinking of the tin even as you are working on it. It was never clear as to what snow load, if any you have. A facia board is an easy add depending on what you want, but not necesary. You mentioned rake trim above and your facia could be as simple as that in itself. Caulking the lap joints is a good idea. Steel ridge with closer strips is probably your best option. As far as fasteners, screws are probably the most common but there are good r/s neo nails on the market. I've had suppliers figure short screws all around. Make sure you're comfortable with the fastener length. Generally the tin hangs over the facia by 2"-3". More will lead to kinking when those February icicles come 'round.

Thanks for all the advice. I have the metal panels already, they are used but in very good shape. The holes are already in the flat, so I am going to use screws. The old screw holes are like 30" apart, so that will be the spacing I use for the purlins. I thought if I add the 2x4s for purlins, it would give me an easier install and I also have something to put my foot against every 30 inches (roofing is not my favorite - the roof is not super steep - but its not a 4/12 garage roof either).

Gary has it we put steel over wood shingles 20-30 years ago, still there with no problems. Use the foam strips under the ridge cap. If you choose under the bottom to keep wasps and such out of the ribs. We use the screws on the ridge tops with 21/2 inch screws. The cheapest steel I have found is at Custom Metal Sales in Greenfield IN Can get colors to 24 gage. Rainbow is there cheapest. It is not what it sounds like. I will let them explain that. Can get lengths out to more than 40ft.
I just got 17,000 SQ Ft for $1525.00 including the trim for ridge and roof ends with flashing for the wall to roof. No I don"t have any vested interest in the company.

Mark B - This is getting complicated, but here's been my erxperience;
Barn, trusses on 4' centers; I've used SPF No. 2+ / SPF No. 3 2x4 lumber, spaced on 2' centers going up the rake. The spacing works well, however I've had to be very careful setting the screw-gun clutch so I don't strip out the screws. The wood is soft.
Older House, leaving existing roof on; I've used 1x4 #2 & BTR KD white pine, on 2' centers going up the rake, because the wood is harder, and the screws do not stripo out. It has always worked well. The 1x4 is OK becuase it is resting on the shingles.
Barn Shed; I've used 2x4 TREATED #1 KD-19-HT SPIB pine, on 2' spacing going up the rake, becuase t will get some condensation ovewr the years, and I dont' want it to rot away. The wood is hard enough the screws hold well. I'm glad I did this.
Sorry for any confusion, I assumed the sort of wood we use around here is like taht all over; my mistake.

Just recently got a lumber quote from the lumber yard for a new house project. Looking at the materials list, a 14 ft. 2x4 spf costs $3.84 and a 14 ft. 1x4 spf number 2 pine cost 4.71. Why would you want to mess with 1x4's trying to attach them over a shingled roof when 2x4's are cheaper and easier to work with? On the old hip roof barns we used to retin, we always used 2x4's and ring shank pole barn nails to attach them to the roof trusses. We never had a roof blow off. Some one mentioned going with treated 2x4's. You have to use galvanized nails and screws with the new treated stuff or the nails can corrode off because of a chemical reaction to the treating now used.

FBH, thanks for the clarification.

Better hope the holes on each sheet are in the same line as the next sheet or hitting those 2x4's may be a problem. With that said it might be easier to hit those 1x12's.

Hitting the rafter when you fasten down the 2x4s will be a challenge as well.

Gary

I guess everyone has a opinion, but here goes for me. I have been doing metal roofs since 1964, and have yet to have one come loose.

We use 2 x 4s, 2 ft on center starting at the bottom, and the last run can be up to thirty inches. We always use 2 x 6 on top and bottom.. The bottom has to have a 2 x 6 if you ever plan on usung over the roof hangers for eve spouts. Otherwise the top hole on the hanger never gets into a board.

One inch limber is usualy made for starting fires, and cost more than a two inch lumber. Placing the lumber just under the lap on any shingle helps keep it from tipping up, and then your tin will wrinkle if the screws are tightened on the metal because the lumber does not lay flat on the roof.

We have never tried to hit the rafters, two guys tack each end with a pasload nailer, and another third man comes and nails them down. The ground crew must hury to keep lumber tipped up fast enough. You are limited to usualy three and a half inches with a nail gun. The time spent trying to hit a rafter is usualy a problem anyway.

We screw 2 inch screws on the lap, and then one just behind the lap for a saftey screw. The bottom gets a screw on every rib, and one on each side of the rib because that is where the wind usualy plays with steel.

If a man has a problem hitting a 4 inch board, he best get off the roof. We always use a pasload nail gun (finish nailer) without any nails to punch holes in the tin, unless we are using Menards steel, or any other cheap steel with a low tencil strength.

Steel nowdays is poor quality, and you must walk on the two by fours, otherwise you can ding up the panels of steel. If it is a low pitch roof, or real long sheets, use the rope calk on the side lap. The reason is because any time it rains hard enough to make the water run off 1/2 inch deep, it will run sideways through your side lap.

We at one time used calk for this, but found out that some calk is corrosive to the metal.

As said, everyone has a opinion, but if you choose a panel that the top side lap.........stops as it heads towards the roof...NOT towards the roof, then a little bit sideways......this is good. Otherwise you can look into the seams. Ever notice the seams in some roofs...standing out for attention? If the lap is towards the roof, you can not see it. On a new building, this is not so important, because the surface is pretty even, and straight.

Most ridge cap is 14 inch, and we have yet to find a perfect closure strip, usualy they get brittle, and the wind moves them around a bit after several years.

Place one side of the roof on, then install the ridge cap, never try to straddle the roof with both sides having slippery steel on it.

Yes the wind will blow the second you prepare to start roofing.......just a fact of life.


We have been lucky, but I have tried to fix others problems with a leaky roof. Most often it is a human error, and 90% of the time it is because the screw was not shot in perfectly straight.


Placing steel roofing on a building usualy impresses the customer because it goes on fast with a experianced crew. So go slow, otherwise your neighbors, and friends will want you to help them on week ends.....you know! It will be fun to do it on the weekends for your friends.