Box profile roofing thread

[tonyshouse]

Yes, we put them 75 mm up under the ridge piece and secure them in place with roof mastic, supplies with sheets if you ask for them, also usefulat the bottomif single ply or stepped sheets.

[Rattyjohn]

25 minutes ago, ProDave said:

Thanks for the picture. so you cut one of the verge angles like that I take it?

 

Yes, the overlapping one is cut. As @tonyshouse says, the foam fillers were supplied with the sheeting and fit under the ridge covers and also at the eaves. A couple of cans of spray paint of the correct RAL colour were also supplied to coat any cut edges and also for future touching in if needed.   

[Roger440]

On 06/11/2016 at 17:15, ProDave said:

Joining them is not the issue. Waste is. My roof is 3.6 metres long, so a 3M length and a 1M length would do nicely. Having to buy two 3M lengths is just "wrong" I can see me designing my wood shed to be a pitched roof 2M long JUST to use up the offcut.
 

 

That would drive me nuts. My garage had them all delivered cut to length, so no joins. Longest was 6.5m if i recall.

[Crofter]

Another question:

 

How high up the roof should I put the first battens? My guess is that they should be around the edge of the ridge cap?

[ProDave]

That is something I have to work out.  The builders already fitted mine, 600mm apart, and about 200mm up from the bottom edge and similar down from the ridge.  If the ridge ones are to far down for the fixing bolts of the ridge piece to screw into, I will have to move them or add another one.
 

[Crofter]

Just off the phone to the people at www.steelroofsheets.co.uk and they were very helpful indeed.

Battens should be 50-100mm from edge of sheet, the greater the unsupported overhang the more at risk it is from wind lift.

I said that at the eaves due to how the detailing works I cannot get a battens closer than about 150mm, he said that would probably not be a problem so long as it's not too exposed. I think that whilst my site obviously is very exposed, the steep pitch of the roof and the close presence of the guttering, with just a narrow 25mm gap from the fascia to the sheeting, will all greatly reduce the force of wind getting into that gap.

 

Also, usually people fix the ridge cap with stitch screws (i.e. metal to metal, so need for a batten to line up).

[Crofter]

Does anybody know anything about using sealant on a metal roof? On the Accord website there is an an option to have them supply butyl tape but there wan't any advice on why it might be necessary. They don't suggest where to use it but from the suggested quantity it appears to be enough to seal all the overlap joints.

I wouldn't have thought that this was necessary, but wondering if anybody else could comment?

It'd be just one more fiddly job to do and I'm tempted to dispense with it, especially given my relatively steep roof pitch which should help runoff.

[tonyshouse]

We always seal the long joins on insulated sheets, there can be airtightness issues if you don't and sealing on the warm side of the sheets is important to stop pumping of interstitial condensation onto the cold parts which can then appear to be roof leaks.

[Crofter]

Thanks for that- it's quite a different application though; my roofing is above a ventilated and drained cavity.

[tonyshouse]

It is possible for water to track across an overlap join so good to use the sealing strips

[ProDave]

Well the prices are in.

 

Steel Roof sheets.co.uk  quoted £405 including VAT but not carriage with "phone for delivery price" and when I told them where I was they said delivery would be about £500 and they would get a quote for that if I really wanted.  Er no thank you.

 

Planwell were £516 including VAT and delivery.

 

Then I tried the two local merchants.

 

Travis Perkins were £342 including VAT and delivery, and Jewsons were £329 including VAT and delivery.

 

so Jewsons have the order.

 

The lesson there seems to be forget the specialist and just go to a builders merchant.

 

[Crofter]

My best quote so far has been from Excel, who @Rattyjohn used, but I haven't asked them about delivery yet. 

 

@ProDave Did you bother with the anti condensation lining at all?

[ProDave]

No. I didn't bother with the anti condensation lining.

 

The only bit that may be "bothered" about a few drips of condensation is the timber purlins that it screws to, so these will be treated with preservative, and then a layer of DPM stapled to the top, so any drips will just run off the DPM and should never wet the wood.
 

[ProDave]

Well my roof sheets arrived on Friday, and today we got most of it up. the main sheets of roofing on both sides and the main length of ridge piece.

 

Tomorrows job will be cut and fit the verge cloaks, and cut and fit the second, smaller section of ridge capping.

 

No photos yet as it was just about dark (before 4PM) when we finished today.

 

just one observation, I encountered man's worst invention today. Plastic headed screws.  Yes all the screws that were supplied to fix it down have plastic heads. Just about okay if screwing into a lovely soft bit of wood, but hit the slightest hard bit and the head strips, leaving me to finish tightening it with a pair of mole grips.  Perhaps that's one thing to look out for, is avoid plastic headed screws.

 

 

[Crofter]

Are these screws of which you speak an alternative to the type where you use a separate plastic cap to cover the head?

[ProDave]

Yes. The "plastic cover" is moulded onto the screw head and not removable

 

If I had known there was even a choice, I would have specified proper screws with a metal head, and a separate cover.  I will photograph them and post a picture tomorrow.
 

[joe90]

When I fitted steel sheets onto my garage roof I was advised against the anti condensation "flock" lining as it's only any good in open structures like barns that can dry the lining with a large airflow , instead I used a roofing membrane to carry any excess condensation away to the gutter. I had metal screws with plastic covers, far better in my opinion as they were tough enough to drive through the roofing sheet without drilling, just a centre punch to create a pinhole.

[Ferdinand]

When I did mine I ran a bead of silicon along the understand of the overhang at the bottom a couple of inches back to make sure that any water trying to run back up there dripped off.

 

Fedinand

[Crofter]

6 minutes ago, joe90 said:

When I fitted steel sheets onto my garage roof I was advised against the anti condensation "flock" lining as it's only any good in open structures like barns that can dry the lining with a large airflow , instead I used a roofing membrane to carry any excess condensation away to the gutter. I had metal screws with plastic covers, far better in my opinion as they were tough enough to drive through the roofing sheet without drilling, just a centre punch to create a pinhole.

 

Thanks- so that's a vote against anti condensation lining, then.

When you say you used a membrane, would you not need one anyway under the roof, regardless of final covering?

[joe90]

Hi Crofter, no it was just a garage/workshop but I didn't want condensation dropping on my tools ?

[ProDave]

Finished it today:

 

 

 

And here are those plastic headed screws:

 

 

[joe90]

Yes I used some like that a few years ago and was not impressed at all, dead easy to strip the head. Nice looking roof ?. Interesting to see the fixings in the raised profile, my garage roof is fixed in the flat section ( yes counter intuitive) but I confirmed with the supplier it was the right way to do it.

Edited December 6, 2016 by joe90

[Crofter]

I was under the impression that on box profile, you fix on the flats (easier to get a nice positive fixing?) whereas on corrugated, like me, the fixings go on top of the section. I assume that with a curved section you wouldn't be able to get a good enough seal if it was in the dip.

I have seen little hollow tubes that you use with Onduline, the fixings go through these after going through the roofing, and this lets you drive the screw in tight without it deflecting the roofing material. Perhaps Dave used something like that?

[Cpd]

I was told that when fixing corrugated sheets if they are above a certian pitch then you fix them in the bottom of the valleys as you can screw it down good and tight without distorting the tins profile, however on low pitched roofs i was told to put the fixings on top and be carfull to not over tighten the screws..... I have done both methods and there is no sighns of leakage after many years.      

[ProDave]

Well I just went by the fact they sent me two packets of screws.  Short ones for screwing metal to metal for the ridge and verge pieces. And long ones that were long enough to screw through the ridges and still have plenty to bite into the purlins.

 

This is narrow profile ridges and tightened to the point you just see the metal start to deflect.  To me it's obvious that little water runs down the ridges so that's the best place to fix. If you drill the valleys then it's obvious a lot more water will run there and it's so much more important that any fixing screw seals 100%. Again being relatively wide valley sections, you might argue if fixing through the valley you would need two screws in each valley section, one at each side.

 

I also pondered whether to screw into every ridge piece or every other ridge piece. I counted the number of screws they sent and there was just enough to screw into every ridge (I had just ONE of the long screws left over)