Stress calcs. for the intellectually challenged

I acquired an ordinary national certificate in mechanical engineering some 40+ years ago, unused since.

Can some kind person direct me to a source for understandable formulae for working out approximate purlin loading on a simple pitched roof? I assume the existing trusses will be adequate.

I am replacing a time expired corrugated steel roof and am considering using composite roof panels which are much heavier:-)

The original building is Victorian/agricultural but I can't see any evidence of an earlier slate covering and the truss/purlin spacing is only suitable for rigid sheeting.

Having just glanced at a chapter on theory of structures (Mitchell, building construction) I fear I may be heading for deep water:-)

regards

Reply to
Tim Lamb
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Best advice if it's just for information, not for building control, is to get the demo version of Superbeam (its free). I worked out my roof design using that, and put it on plans for building control. They then demanded some structuiral calculations for which I had to pay 80 quid, which showed that my design was OK (which I knew). The calcs by a qualified structural engineer took up about 15 pages and gave me a nasty flash-back to A-level physics. Simon.

Reply to
sm_jamieson

Why not just replace the "corrugated iron" sheets? Last for ages, cheap, easy to put up.

Reply to
Chris Bacon

Would have almost been cheaper[1] to cough up for Superbeam so you could have printed them off yourself!

[1] well not quite, but at least you would have a nice bit of software to play with after ;-)
Reply to
John Rumm

Yes. These have lasted around 60 years. I suspect they were good quality at the time.

Unfortunately moist air condenses on the underside of cold steel sheet. This is particularly apparent when such buildings house cattle on deep litter and there is a frost.

Anyone repairing or modifying traditional farm buildings has to consider future alternative uses. My intention is to convert what was a milking shed with standings for 12 cows to house the farm woodwork shop. Gluing at less than 10 centigrade is a problem and I may need to put in some heat.

The proposed panels have 80mm of insulation and weigh 11.75kg/m2.

regards

Reply to
Tim Lamb

In message , sm snipped-for-privacy@hotmail.com writes

OK ta. I'll have a look this evening. If the building ever comes up for a change of use, I will have to sort this out properly.

regards

Reply to
Tim Lamb

Seems like a fine opportunity for combined roofing and solar heating panels, depending on your orientation. Good luck with the calcs.

Reply to
Mike Halmarack

A friend has a garage with a flat roof. He wants to put a pitched roof on. The roof is merely for looks as the flat roof is waterproof. The garage roof will not be big at all as the garge can just about fit a Cavalier car. Would Building Control need to be notified and would they require stress calcs for such a simple small roof? A cut roof using 2x4s would be well strong, and I can't see the need for calcs in this instance as rule of thumb is more than good enough.

Reply to
Doctor Drivel

How much is Superbeam?

Reply to
Doctor Drivel

£149+VAT

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waiting for Tony to do us the uk.d-i-y special discount version though! ;-)

Reply to
John Rumm

I'm am forever being told that we sell it too cheap so everyone is getting the discount price!

Reply to
Tony Bryer

Yes, this is when it can really be cost effective. Panels and roof covering are one and the same thing. How much hot air could it produce during winter? at what cost? How much more is this than plain roofing cost?

NT

Reply to
meow2222

To be honest, I agree! ;-)

(I would not have been suprised if it came with a price tag in the £300 to £600 range)

Reply to
John Rumm

Thanks! Knowing what to charge is hugely problematic with something that has a minimal marginal cost per extra unit supplied. I have no doubt that the vast majority of those who have bought it and use it regularly would

*now* feel that it is worth more, but keeping the price lower encourages the less certain to take a chance - £149 is not nothing but it's not a disaster if it doesn't work out. And, more importantly, we haven't left much of a price hole for someone else to come in and fill - a few have tried over the years but never lasted.
Reply to
Tony Bryer

In message , Mike Halmarack writes

Thanks.

East/West so OK but...

With a largish river 20m away I'm more inclined to a heat pump.

I don't know if o/p temperatures would be high enough for under floor heating but I will bear it in mind for any future change of use.

regards

Reply to
Tim Lamb

Current estimate for a roof 4.5m x 13.5m (in plan) around £1500 using

*seconds*. A lot of the cost is in the fixings, ridge, gap closers, barge boards etc.

I have no idea what the cost would be if half were in solar panels. Presumably I would still need a conventional heat source as a back up?

regards

Reply to
Tim Lamb

I suppose if it was too cheap, people accustomed to paying £xxx for Autocad etc would not take it seriously.

Owain

Reply to
Owain

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Tony Bryer saying something like:

Superbeam and Superheat are really excellent items. The demo versions will do me for just now, but if I start needing them seriously I'll have no hesitation in paying for them.

Reply to
Grimly Curmudgeon

A water sourced heat pump extracting from a moving stream or river is by far the best system.

Reply to
Doctor Drivel

Lay the iron over 1/2" Sterling board. This works well. Then again, you're adding weight...

Reply to
Chris Bacon

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