# Forum Home Renovation Roofing  Tiles vs Colourbond?

## piscean

we have an old concrete tile roof which really needs replacing. I think clay tiles are the best option but DH wants to go with colourbond but I'm not totally sold on the colourbond roof idea.  
are there any pros and cons to colourbond? does anyone know the likely life span and are there any structural changes that need to made to convert?  
The things I'm most worried about with the colourbond are leaks and noise from rain etc, are they likelly to be an issue?

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## SilentButDeadly

Archicentre quotes colorbond roofing as typically a smidge cheaper to replace than a tile roof.  But that deponds on the complexity of the roof design. 
Depending on the state of your roof timbers you may need new battens.....up to the pros to decide.  This will influence the cost because it'll take extra time to remove existing battens and replace with new rondo or similar. 
Colourbond roofing should last well over thirty years.  Depends on the quality of the installation in a lot of repsects. 
Leaks won't be an issue as long as the install is done well.  Noise is the same but can also be minimised by insulation - we have an insualted tin roof and can barely hear the rain.

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## dukekamaya

Colorbond weighs around a quarter of the weight of a tiled roof - much less stress on the house frame. You would almost certainly need to batten the roof with 70x35 battens. Depending where you are (due to regulations) you may also have to install anti-con under the Colorboand (mandatory in some states)

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## Cecile

I would go with Colorbond every time, simply due to its clean sleek look and it's a no-maintenance roof once installed.  You definitely need anti-con installed under it, which dampens the sound and gives much needed extra insulation.    The roof on our place is zincalume, installed about 20 years ago, but when checked by a roofing contractor he said it was in such good condition that it had another 25 or more years in it.  We elected not to replace it with new Colorbond, but did have it removed, anti-con installed, and the original roof sheets reinstalled using all new screws.  I don't know if the battens are original (house built 1950 or so) or were replaced when the roof was done but they did not need any attention.

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## piscean

Thanks for the repies and comments dukemaya, cecile and silentbutdeadly, I'm feeling more positive about the colourbond now. Thanks also for the heads up with the battens and anticon, at least I know what we're up for and there won't be any surprises when I get the quotes. cheers!

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## Master Splinter

Some drawbacks of colourbond... 
Has a tendency to look dirtier than tiles after a few years (especially around the ridge).
You can't simply 'push a tile back' to get access to the roofspace or wall cavity, for wiring/installing things.
The kliplock stuff is a right $#@!!*&%!!! to remove if you need to get under it.

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## barney118

Not long finsihed my house with colorbond (there is no u in color) cant beat it, it wont let you down in a hail storm and potentially crack and let in water. any movement in the house it will flex unlike clay.
I had to re batten the house, i used 70x35 MGP12 ( as it spans further than MGP10, less battens) it cost me approx $1000 for new battens, i left the old ones there and just put new ones close too if they clashed. I suppose some time in the future I might need to replace the screws/rubberwashers but they are cheap as chips as a maintenace issue.
A must if DIY is to buy yourself a screwgun (or cordless drill) to screw down to a tourque setting and dont over do the rubber washers.
Yes it is guaranteed to fade (colour) overtime the darker colours more noticeable, and most likely to last a lot longer than specified providing you buy Colorbond (TM), be careful of what you buy BlueScope brands its product otherwise you could be buying colormax, or a cheap import. 
The builders blanket/anticon cost me $1000, on the other hand I suppose from a labour prospective it is also cheaper (quicker to put up)

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## rod1949

If you go with colourbond then consider an E-vent for the ridge to ventilate the roof space.  I have a couple on my roof and they just blend in with the roof line and are not ugly add ons like the wirly things are.  They are made here in Perth, here's the link  Combined Metal Industries - Our Products

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## Stan 101

> I had to re batten the house, i used 70x35 MGP12 ( as it spans further than MGP10, less battens) it cost me approx $1000 for new battens, i left the old ones there and just put new ones close too if they clashed.

  
You did the right thing by leaving the existing battens in place. The roof battens also restrain the rafters / top chords of trusses. It's a key point many never look at. 
The other thing to note if you have trusses, it may not be a simple swap tile for sheet and vice versa. I won't go into it here but forces can reverse in a truss (what is in tension in a tile roof may become compressed in a sheet roof during a storm). Also, you will generally need to improve or at least do a few calcs to see if the existing truss / rafter to frame connection to wall is still adequate. 
Also going from sheet to tile would definately require a better inspection of the lintels and possibly the top plates and studs depending on where the dwelling is.  
Cheers,

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## piscean

splinter, I've never noticed CB looking dirtier but then again most of the CB roofs around here are pretty new so I'll keep an eye out for that. good point about the access too, I think it could get old pretty quickly having to climb through the roofspace everytime DH wants to install something.  
rod, thanks for the link. at the moment we have 3 whirlybirds but I dont mind the way they look but 2 of 3 got damaged in that hail storm in march and will probably get replaced with the new roof so we may go with the roof vents instead next time.  
thanks for the replies everyone. It's sounding a lot more complicated that we thought doing a quick changeover so I'll get quotes on both and see if there's much price difference.  
just one last question, how difficult is it installing stuff on a colorbond roof? e.g. say a flue for a exhaust fan you're putting in etc?

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## Bloss

> The other thing to note if you have trusses, it may not be a simple swap tile for sheet and vice versa. I won't go into it here but forces can reverse in a truss (what is in tension in a tile roof may become compressed in a sheet roof during a storm). Also, you will generally need to improve or at least do a few calcs to see if the existing truss / rafter to frame connection to wall is still adequate.
> Cheers,

  Not an issue if going from tile roof to metal, only if attempting the reverse. Any trussed roof designed to take ceramic or terracotta tiles will be well over-engineered for any metal roof you might put on it. And roof frame design does not rely on the weight of the tiles to counteract wind forces - that is all done by designing fixings bracing etc - between the trusses and onto walls. The forces involved in a tiled roof considerably exceed a metal roof - so when replacing tiles with metal (with battens and fixings to the specs for the sheet concerned) the trusses will be fine.  Different kettle of fish going the other way - and you'd need an engineer to tell you what would be needed.

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## nww1969

I'll stick my head out and go against the trend and go Glazed terracotta anytime.
The new darker glazed tiles look the goods. They finish the house off much nicer and just 
reek quality.   
Colorbond is not completely maintenance free.
I have recently spent a day replacing all the screws on a 15 year old roof due to
the rubber washers perishing and causing some leaks.
And it you live near any type of tree the mold build up can make the roof look dirty.

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## piscean

thanks for the info bloss, very helpful and really reassuring too  :2thumbsup:  
nww1969, that's the type of thing I'm worried about with the colorbond and that sort of job sounds really tedious. at least if you get a leak from a broken tile you just swap it over - easy peasy.  the mould/dirt issue that's been mentioned is a bit of a worry since our house is lower than street level and you see a lot of the roof from the street so if it gets dirty or mouldy it could be really obvious so we wont be able to just ignore it and pretend it's not there  :Biggrin:

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## Stan 101

> Not an issue if going from tile roof to metal, only if attempting the reverse. Any trussed roof designed to take ceramic or terracotta tiles will be well over-engineered for any metal roof you might put on it. And roof frame design does not rely on the weight of the tiles to counteract wind forces - that is all done by designing fixings bracing etc - between the trusses and onto walls. The forces involved in a tiled roof considerably exceed a metal roof - so when replacing tiles with metal (with battens and fixings to the specs for the sheet concerned) the trusses will be fine.  Different kettle of fish going the other way - and you'd need an engineer to tell you what would be needed.

  
With all due respect, Bloss ( Cos I know you know your stuff :2thumbsup: ) 
You got it wrong on this one. When roof truss analysis is done, you design not only for dead load such as the roof material, but for a reversal of loads under a wind uplift event.
When you design roof trusses with a tile roof, especially in non cyclonic regions (n1-n3 generally) the webbing in the roof trusses rarely has a load reversal due to the mass of the tiles. So a web or truss chord that is compression will generally stay in compression and web or truss chord in tension will stay in tension. 
However, when a designing a sheet roof with low mass, the truss is actually designed under gravity and then must be analysed again under uplift. And often the long webs in the truss (usually the ones running from the apex) are most affected. They may stay the same size and go up a grade or jump in size and nailplated joints are also at risk of being under spec due to the reversal of loads. 
Webs in compression under gravity require less 'bite" or less nailplate coverage as the compressive forces help keep the web in place. However, on a tension joint, the timber needs more nailplate to stop the two members from being pulled apart. 
Don't take my word for it, Call Pryda, Multinail or Mitek (the only 3 accreditted nailplate suppliers in Au) and ask to speak to their engineers about this. They will give you a similar reply. 
A structural engineer who does not specialise in roof truss design, probably would make the same assumption you did, assuming the truss to be okay. But have them think through what I've written above, they may be more inclined to agree with me.   
Cheers,

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## Bloss

> With all due respect, Bloss ( Cos I know you know your stuff) 
> You got it wrong on this one.  .  .  
> Cheers,

  On the theory I can't disagree - in practice been there done that with so many roofs I can no longer count. Paid for and got engineers reports and never once was any truss in place previously for tiled roofs needed to be altered to accept metal roofing. 
But - and it's not a trivial 'but' - it was not uncommon for additional tie downs to be required from trusses to wall frames and occasionally some additional diagonal bracing - but across multiple trusses not altering the individual truss design. The reason is that for tile roofs the trusses are closer together (smaller spacing) and most often have larger and heavier members and although different forces are involved (lift is still a factor in tile roofs!) the various differences often cancel out. 
Your point is well made though Stan   :2thumbsup:  - not something that should simply be assumed (I hope I wasn't suggesting that - it's why I have my caveat on each post - just 'cause Bloss says so on this site isn't sufficient reason to not get specific advice on a job).   :Wink:  A major job like altering a roof skin should not be attempted without professional advice. Just because my experience tells me it is unlikely to be a concern hasn't meant that I had simply assumed that and gone ahead - so I got engineering advice on each occasion - so should everyone else contemplating a major structural alteration.

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## Terrian

> Colorbond is not completely maintenance free.
> I have recently spent a day replacing all the screws on a 15 year old roof due to
> the rubber washers perishing and causing some leaks.

  luxury, sheer luxury I tell ya! 
the GLW & I spent a couple of days removing the old roof screws and putting in new ones.
the old ones were slotted head screws covered with a dollop of bitumen sealer, hammer, chisel, vice grips to get them out  :Smilie:

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## dawlew

i would or shoud i say 'wood' agree with bloss, hope i got the name right. 
Anyway, I have done a number of roofs and conversions and have never come across any complications tile to iron except tie downs for the aforementioned uplift factor. 
someone mentioned the ease to replace a tile if broken and gain access if wireing etc. Might I add that a tile roof is so easy to break into. Some years ago a friend locked themselves out of their house, before they could check the car for a spare set I had jumped up on the roof removed a tile found the manhole and met them at their own front door. 
I would go iron over tiles almost anyday, it would be a rare rare occassion i would choose tiles and it would only be for heritage reasons

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## Stan 101

> On the theory I can't disagree - in practice been there done that with so many roofs I can no longer count.

  Just because many houses have made the transformation from tile to sheet  does not make it correct. As mentioned, the only time the change in forces would be noted under a major uplift event.  
The same rationale you use could be applied to the truss to plate connection. A nominal 2 skew nails and a multigrip used for a tile roof would not cause concern to a sheet roof of say a 10 metre span until an uplift event by wind took place.   

> Paid for and got engineers reports and never once was any truss in place previously for tiled roofs needed to be altered to accept metal roofing.

  Bloss, I have no doubt you did your part and got the engineer's cert for the works. I also have no doubt that the engineer simply assumed the structural integrity of the trusses and never gave it any thought whatsoever. 
The reason I make this assumption is due to the time required to manually analyse a single standard roof truss would be prohibitive without the designer software it was originally created with, never mind the whole roof. 
The engineer would need a site inspection and measure positions of all web locations of every truss, would need to measure the size, width and position of every nailplate. Nailplates come in different thicknesses and therefore different shear capacities. They would then need to know the timber grade and size of every member in each truss. The time taken to do this is painstaking.  
Then the analysing of the truss manually has its own concerns. First you need to know the manufacturer of the nailplates and the plates' capacites (not generally available to the public at large. Licence fees are involved) and associated edge distance requirements for hydraulically pressing plates into timber. 
Secondly, the engineer must then manually do the calc on every joint in every different profile truss plus design checks for plate crush, rotation, sheer, bending, compression, overhang deflection and panel deflection. For girders there would then be point loads from other trusses to manually apply to the truss chords. 
The average standard truss usually has about 6 pages of printed A4 showing analysis results. That is software generated so imagine the amount of manual calcs required by the engineer. Now add that to about 20 (give or take) differing truss profiles in a roof. 
The engineer must do manual calc because they would not have access to the three software packages available for design of roof trusses to the relevant Australian standards. There are very few engineers in Australia who specialise in timber truss design and therefore access to the software legally.Without counting them, I'd say less than 25 have that access. Of those who are consulting engineers and have access to the software, I can think of three. 
The next time you consult an engineer for a similar role, just ask out of curiosity, on how he concluded the roof trusses are structurally adequate in their own right. It would be interesting to hear their reply.   

> But - and it's not a trivial 'but' - it was not uncommon for additional tie downs to be required from trusses to wall frames and occasionally some additional diagonal bracing - but across multiple trusses not altering the individual truss design.

  Yes restraint or tie down does change and can change dramatically going from tile to sheet. I'm uncertain as to why the need for additional racking roof bracing, usually by way of steel brace or 'speed' brace as the code does not differentiate between dead loads for residential construction roof racking bracing(up to 16 metre spans.)   

> The reason is that for tile roofs the trusses are closer together (smaller spacing) and most often have larger and heavier members and although different forces are involved (lift is still a factor in tile roofs!) the various differences often cancel out.

  Uplift is definitely a factor in tile roofs. But in no way can I agree with your point that various differences cancel out. It is a misnomer. You are still not thinking about the nailplate connections I briefly touched on in my last post.  
The other big issue could be the bending of the overhang during uplift. The dead load of tile is approximately 50kg/m. The uplift from wind that can be applied to an overhang can be much greater than 50kg/m therefore the top chord of the truss may in fact be of a heavier grade on designed trusses specced for sheet roofs.   

> A major job like altering a roof skin should not be attempted without professional advice. Just because my experience tells me it is unlikely to be a concern hasn't meant that I had simply assumed that and gone ahead - so I got engineering advice on each occasion - so should everyone else contemplating a major structural alteration.

  Excellent points  :2thumbsup:  :2thumbsup:   
Cheers,

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## Bloss

My engineer uses one of them computer thingies - so it is no guessing or assuming or automatic sign offs - his career and business is not worth the risk. Once the engineer tells me its OK it's his insurance company that carries the can if its wrong not mine! 
The program is the same as used by truss manufactures to design the trusses and he is able to run the numbers based on the roofing 'skin' and it tells him that the existing roof is OK or not. Access to that is not as rare as you suggest (well not in the ACT anyway). Nor is the sort of manual work you suggest needed or done. 
There is in fact much less variation in components and design and assembly than you describe - like all assembly line factory products standardisation is the go and few designs will not be done to very high safety margins as in timber truss design the additional cost of doing so is not great relative to design to a minimum. 
Additional things he tells me to do are often 'belts and braces' - as they are easy to do once the original roofing is off. 
In any case the sort of extreme events you contemplate are rare and as there are significant number of roofs changing each year from tile to metal - and often without any engineering advice, just a roofer or chippy getting in and doing it, and there have been no mass of incidents of flying roofs then on a cost benefit basis alone it seems not to be a problem - again the theory is correct, but in practice people just take the risk - and mostly they are right as nothing happens! Of course anyone who as seen damaged roofs from extreme events (and I have) will tell you that the best designed roofs can come off even if built as designed, and too many are simply not built as designed - and you find out often in far less extreme events than the design might withstand. 
But I suspect we are in furious agreement - my last point about getting professional advice is the key.

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## Stan 101

> The program is the same as used by truss manufactures to design the trusses and he is able to run the numbers based on the roofing 'skin' and it tells him that the existing roof is OK or not. Access to that is not as rare as you suggest (well not in the ACT anyway). Nor is the sort of manual work you suggest needed or done.

  So you are saying that without the engineer even knowing what is on site, he can run the comps and make the assumption that it will be fine. Bloss that simply makes no sense at all. I'll continue to bet the engineer you use is not using Mitek, Multinail, or Pryda software and therefore can not do a full analysis on the trusses. But again I'll make the point that even if he were using one of those three pieces of software, how does he even vaguely know what is already on site without even inspecting it or having the fuill original comps? 
You are aware, are you not,  that all three design packages allow individual manipulation of webbing for individual trusses therefore the panel spaces of said trusses may be anywhere from about 1800mm to 3000mm or greater. So without the original job design (only available from the original truss detailer) how does the engineer know what he is dealing with in the first place? 
I just ran the comps on an 10000mm span standard truss with tile roof and N2 windspeed that passes and then reloaded it with a sheet load and guess what... Shock horror! It failed in bending on the centre web area. 
Again, like I said earlier, don't take my word for it, next time you order a set of trusses bring it up with the truss detailer and see what they have to say about it. 
Like you mentioned, though there are not roofs breaking everywhere, but again there were 50 year old houses in North qld clearly not built to current spec that survived cyclone larry, but there were plenty more that got flattened, some using the 1989 code. 
As I have mentioned earlier in this post, the failure would only possibly occur in an extreme wind event. I have seen failures directly occuring to this nature on the gold coast, in Bundaberg, Brisbane and in Northern NSW. The failures were not catastrophic but failure resulted in massive deflection of the bottom chord and therefore ceiling when the underspec webs buckled in compression. We could check this by simulated modelling and the results were consistant with what was on site. 
Bigger failures do happen and yes people do die. The Riverside golf club in SA is testiment to that.  
cheers,

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## Bloss

Last post on this one Stan. 
I have rarely had an engineer do anything for me without coming on site - and taking direct measurements of what they see. The as built structure is what is used as the reference point. The exceptions is if the original truss specs are available - and in the ACT that is generally the case as the local authority isn't bad at record-keeping at least. 
This is all about cost benefit and likely risk - and all buildings are done to a price and an 'acceptable'  level of risk. We simply do not build to withstand extremes - the standards simply try to make a reasonable compromise between performance and cost. And mostly they get it right. For when they get it wrong we have insurance - it is cheaper to insure when the occurrences are low/ infrequent and consequences high. 
Extreme events are uncommon if not rare and we simply do not build normal houses to deal with them. If a house life is 50-60 years or even 100 years we do not spend too much money making them withstand 1:100 year events and even less to withstand a 1:500 year events. Even though we mostly know how to build those structures. 
So I am back to theory vs practice - in this case changing a roof skin from tile to metal. IMO there should be no tile roofs north of Port Macquarie - anywhere cyclonic wins might occur, but there are. They are constructed for the local wind zone and all I suggested is that advice be taken before changing - I think that's reasonable. If the advice turns out to be wrong and the roof blows off - that's why we have insurance. 
I know that people get killed in extreme events - but in this country driving is much more dangerous, falls kill and injure more people than cars let alone the early deaths we cause ourselves by lifestyle habits (eg: over eating & smoking) and we just have to judge risks for ourselves (and we mostly are pretty bad at it! See: http://www8.abs.gov.au/ausstats/abs@...2?opendocument ). My judgement is that this risk (of massive roof damage after changing from tile to metal after advice) is very very low.

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## Stan 101

Bloss, I am talking about relevant australian standards. The only reporting submitted to LGA and certifiers is the reaction or council report. This report simply states the tie down reactions for the supporting members such as walls and beams.  _No information at all is submitted regarding the individual truss internal designs_ for residential housing in Australia. 
This is where I think you are being confused. Here is an example: 
One truss detailer could design a 25 degree roof truss with a 9000mm span, a 760mm overhang and use four internal webs. This will design fine though the deflection levels and the truss members and nail plated joints may be working close to 90-95% capacity. 
However, another truss detailer may create the same external profile of the truss incorporating 5, 6, 7, 8, or 9 webs reducing the internal forces runnng through the individual members and possibly reduce nail plate sizes, web and chords meber sizes and grades. Having four or 9 webs in a truss will have little to no result on the tie down requirement at supports( the extra self weight MAY be noted in dead load) 
This profile of the truss is not released to council and is locked in the database of the truss detailer who created the job. The council report has no information whatsoever on how stressed individual members and joints for trusses are. No certifier or consulting engineer would have a clue how close to capacity the joints or the members are working. Hence my earlier posts on manual computations. Without the source info, they are simply assuming and I fail to recall anywhere in the relevant AS's as to where assumptions are accepted, except for the assumption that a structural fascia is used in all dwellings. But that is a whole new post.  
So I say it again, from what you have mentioned, your engineering is simply making an assumption; and assumption that clearly may or may not satisfy relevant australian standards. This is the fundamental point to my posting. I understand what you are posting but you are completely ignoring the 'next step' to design analysis to confirm the individual trusses will work with the new uplift loads as per AS1649, AS 1684 and the ABCB handbooks.. 
Span tables have not been used for roof trusses in over 30 years. The truss software these days have an incredible ability to design any configuration the truss detailer chooses to use regarding webbing and to transfer load from roof to floor to wall to slab and any other structural members such as steel. This can lead to these other members working as supplementary bracing members in designs that had always been designed as individual sections such as roof, then floor and then wall. 
The outcome of this can/will mean major ramifications to home renovators in future because even the original builder may not be aware of what members will have adverse effects on other members if modified.  
Your judgement on the risk being very low is something I agree with but in this country we build to relevant australian standards. Your judgement does not conform to Australian standards in this case; specifically AS 1649-2001. So where do we draw the line. Where and in what instances to we start to ignore australian standards just because there is a low / minimal risk?  
Do you disregard AS1684 and the timber framing span tables within, too? One is equally as important as the other in this instance. So why accept one AS and not the other?   
Regards,

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