Oversheeting a corrugated cement fibre flat roof with steel

The garage roof was cracked and leaking but before replacing it, I fortunately discovered thin steel sheets which go over the top. They're available in Big 6 which is what I needed, 0.7mm thick, vinyl coated on the top and painted on the underneath. Using these saves a lot of effort and the cost of a skip.
I dunno how the pro's do it but this is what I did to minimise the need for another pair of hands and the time spent up on the roof.

First draw your roof.

This is a scrap plan done in Excel.

To the North is another garage 14.75" away

To the East is reasonable access from grade apart from the bottom corner

To the South is a garden with all sorts of obstacles including a trellis going further south, a tall clump of bamboo, a pond, various junk and more junk.

To the West is a workshop, roof is about 18" lower than the garage so ideal for supporting a board for access.

The sheets come in 10' lengths. I could've bought them in more friendly sizes to match the oddly spaced purlins but at quite a cost penalty so I didn't. This works with 7 sheets, 1 being cut into 1/3rds which are the yellows.

Incidentally, the 1/3rds weighed 7.1kg so the full sheet weighs 23.5kg including a bit for the kerfs.

I used an angle grinder for the cuts and a powerfile for the cleanup but if I did it again I'd buy an air powered nibbler. Quicker, no cleanup and no busted discs.

Next think about how to lift the sheets.

1st thought

Push sheet up ladder and let it tip over

Probably ok if you're tall and don't mind being under the sheet during the lift, but any mistake like a trip and it can slide back and take off bits that you'd probably sooner keep. Think on.

Then I discovered the combination ladder

It's pretty versatile with stabilisers

that can be offset to get closer to an obstruction like a wall

or you can add a wedge if the ground is sloping. Hopefully it's obvious that the Stanley knife was used for the purpose of illustration; if not, I'd recommend you stop reading.

but I digress

I'm interested in using one of the hinges as a hinge.

3rd thought

Lift and support by prop clamped in workmate

then hop up onto 2nd workmate and slide the sheet onto the roof from the side.

So here it is, imagine a sheet on the top, also imagine the door painted whilst you're at it.

Hereinafter, this shall be called the front for reference purposes.

Incidentally, the vertical strut and the beam it’s supporting are repurposed ladder stiles. I needed another ladder about 2m long for the job so I cut down my extension ladder – seemed a shame but it hasn’t been used as a double in 25 years so rather than buy something new I angle ground it.

The rungs of the offcut were cut off which resulted in two useful lengths that were used to replace the original wooden bits, much stronger and stiffer.

Detail of the anti-slideback device on the original wooden setup, it's hinged so the sheet slides over then it flicks back and the sheet is lowered onto it before lifting.

How to move the sheet once it's on the roof?

A trolley

made from 2 -  2"x1"s, 2 - 2" plastic pipes, 1 - broom handle and a few holes. It's 5' long as I hoped that the sheet would land just past the pipe at the back once it toppled over. Grade access at that side is restricted by a fence which runs on an angle from the corner of the building so the sheet had to be positioned more to the centre of the roof then slid sideways into position

It worked

This is after lifting and pulling it over into position. The plastic pipes are so effective that the sheet runs back down the roof gradient by itself and needs jamming or a brick to prevent it falling off.
The Mole grip indicated the edge of the trolley so I knew where the sheet needed to be aimed, the ladder's used as a duckboard so I could pull out the rollers.
I bolted a castor to one of the stiles which helped moving it along the roof.

Next up was the 1/3rd sheet which I did from a side ladder.

Next was to be the back sheet. The trolley wouldn't survive the journey without falling apart and I needed a rope to pull it from the back end so

this shows a pipe roller at the back with the rope going all the way to the front and a bit further.
Detail.

The rope goes through the pipe and is secured to the G cramps with clove hitches.
After lifting, the rope is thrown to the back of the garage and the sheet pulled into place. No video I'm afraid but it worked well, in fact, the last two sheets took an hour from ground to final position.

Have you spotted the mistake?

Yes, I should've worked across the width first then moved backwards but I realised in time and got away with it as the first three sheets were fixed only at the left edge and the middle one was short.

Safety

• Do it wrong and you can hurt yourself
• Do it very wrong and you can die
• However you lift the sheets don't stand under them
• Don't work if it's windy
• Don't do it unless you're very diy experienced and skint

PPE:

• Shoes not sandals
• Bins - eye protection when grinding
• Ear defenders
• Proper work strides with knee pads in leg pockets just at knee height, a gift from the gods when crawling along a horizontal ladder. Don't use strap on pads, there is no comparison.
• Gloves when handling the sheets

Cleaning the old stuff

I may have gone a bit overboard but I scraped off the moss and crumbly bits with a shavehook followed by vacuuming. If any detritus is detached during the lift/ positioning then it will probably fall into the valleys and rather spoil the profile of the sheeting. You'll only get one chance.

Fixings

The existing roof was fixed with hook bolts which were all the rage at the time. The supplier couldn't supply them and advised that they weren't used much anymore. He suggested Baz fixings which are self drilling, thread cutting screws with a waterseal.
Well I'd never heard of them and didn't really fancy drilling the purlins but a quick search found a video clicky which was very impressive showing a quick operation from the top only whereas hook bolts needs someone inside the garage. Anyway, I was hooked, or hookless, depending on your viewpoint.
So I had a practice with a piece of scrap rsa similar to the steel purlins on the garage. To be honest, I lost the will to live during the drilling as it took so long then my girly drill didn't have enough puff to cut the thread.

Actually, it's pretty good, 430W but no gearbox so it failed.

Plan B
Pilot drill first with the girly then use a mans drill for the threading.

I've had this for years, it's brilliant, 750W, two speed gearbox, soft start, variable rate hammer.

Bingo, that's the way to do it.
So I bought two nice new cobalt tipped bits. One did four holes before it blued, the other did the rest. Not sure if it was variation in quality or whether I drilled a couple without enough lubricant, the cement fibre is pretty abrasive so maybe it was that.
Talking of lubricant, I used this stuff

 and it's very good.

Top tip - don't bother with a centre punch, run the drill slowly backwards for a few rotations, it'll make a little crater through the vinyl and slightly into the steel. Then spray crater and bit with lubricant, change to forwards and go. The bits are a little short and need minimum chuck engagement, even so they couldn't get all the way through the purlin but the Baz screw eventually penetrated it.
There's something called a Bosch Multipurpose Drill Bit which looks like a better bet than the cobalt jobbers.
Which reminds me of my set of ASBO drills that I'd forgotten.

It's slightly longer which would've penetrated the purlin, I'm a bit cross about the memory lapse.

Update: It wouldn't have mattered, the ASBO and  Bosch Multipurpose Drill Bits aren't sharp enough and skate all over the place so you need to use a steel  cutting drill first. Ideally use the steel cutter to penetrate the, err, steel then a masonry drilll to go through the cement fibre then the first to go through the purlin then the third drill to drive the Baz screw in. It's bad enough with two drills and their cables up there let alone a third.

Something old, something new

Self drilling, self threading Baz screw is of plated steel, the washer is stainless and the plastic cap goes on the top. The wings cut a clearance hole to allow for thermal expansion Graeme ;-).

Supplier

Tinman Steels Ltd of Tamworth. A smashing company to deal with, fair price, good delivery and very helpful over the 'phone and email.

Crikey, how did they know this?

A bit more on ASBO drills

The tips are welded in rather than brazed like a masonry bit so there's no braze to melt and the tips won't fall out. I bought these from ASBO in Teddington years ago, the chap there demonstrated them by drilling through a file at high speed with it all glowing red. They're not much cop on wood as the timber is torn out rather than cut but they're great on concrete and will go straight through any rebar.

Sadly they seem to have packed up.

A bit more on the combination ladder

Absolute bargain at £36 and a few coppers at the local Homebase. It also has steel sheets to turn it into a platform.

Anyone want to buy it, one careful owner, limited use, only a few holes in a couple of the treads?

Leak test

It's hardly a monsoon but it's good to look at the cracks in the old roof and see nothing dripping through

Wow, according to word there are 1648 words, did anyone get this far ;-)

Front fixings

It's a concrete lintel that I don't want to drill. Can't buy hook bolts locally so I modified the u-bolts used to support the roller earlier. Originally from a satellite dish mount, they're well galvanised, now waiting for the paint to dry.

Top seal digitally tooled with spit.

Penultimate task

Infill below the old sheets to the lintel. It was originally done in some black gunge which perished, polystyrene eaves fillers are avaible locally but not in Big 6 so I bandsawed them out of 3/8" ply.

Last task

is to mastic the joints and add further bolting to clamp the front of the blues to the yellows and the front of the yellows to the pinks because of the odd purlin spacing.

Being tight, I wanted to use up the Baz screws so I reused the anti-slideback device.to make 'nuts' to go underneath.

Eagle eyes will spot the rust from the staple that went through the label