roof trussed rafters bracing question

Hi,
I have recently bought a new house and had a fairly decent survey done. One of the points that was brought up was about the roof bracing internally. The phrase used in the survey was:
The roof structure consists of trussed rafters which appear in satisfactory condition. However, the trusses are only partly braced and this bracing should be brought up to full modern standards.
Can anyone elaborate on what 'full modern standards' means? If its a case of hammering some wood in with nails I will do it myself rather than pay a joiner.
The house was built in 1978 and my neighbour that has lived there since then has never done anything with the roof. The surveryor classed this as medium priority. Then again, replacing the garage light was also medium..
Thanks,
James
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In an earlier contribution to this discussion,

What do your trusses look like? Are they like the one illustrated in http://www.dontim-eng.co.uk/downloads/section1.5.pdf - with an outer triangle made of ceiling joist and two rafters, and internal bracing members forming two V's? If not, which bits are missing?
If you're worried, you'll need to get a structural engineer to calculate what additional supports are needed.
Alternatively, pretend you are building the house now, and get a truss supplier to specify what trusses would be required, and compare this with what you've got. [I have a vague feeling that one or two truss suppliers have on-line design facilities into which you can enter your data - but I can't remember where I saw it - and may even have imagined it!]
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Cheers,
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wrote:

members
James
I hope that by "bracing" they mean bracing and not individual members of each truss.
One truss should comprise a ceiling rafter (horizontal along the bottom), two sloping roof rafters which together with the ceiling rafter form a triangle. Within this triangle there should be probably be (on each side of the apex) a minimum of two other timbers forming a Vee or if the truss spans a long way (big house) maybe a W.
The bracing that I hope they refer to should connect the same points of all the trusses - ie parrallel to the joints in the roof tiles and should be be 4" x 1" timbers nailed to the node points (where the internal members of each truss meet the rafters) of each truss.
Additionally there should be diagonal braces - best described as going from bottom left of the roof to top right (viewed from outside) ending at the gable wall at the apex of the roof to keep all the trusses vertical.
Missing bracing is quite common in '70s housing stock. sometimes it is bad news sometimes it isn't.
The best way to tell if you have a serious problem is to look at each truss individually. If it is "plain" ie it could be laid against a flat surface with no gaps you don't have a problem. If the truss is bending sideways in the middle then you have a problem. This can be spotted without looking at the trusses in the attic. Look at the roof tiles from the outside. A diagonal line up the corners of the tiles should be straight - if it is a noticeable curve only one way then the trussed rafters have buckled due to lack of bracing. Don't worry if you can approximate a straight line with odd tiles each side of it.
This is really hard to describe in words and 1000 times easier in pictures.
I'll look for some links of what bracing should look like
Jon
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I'm told it was normal not to brace them in the 70s. I've never heard of a single case of the roof collapsing as a result, although it wont be as rigid and resilient as it would be if you brace it. Surveyors always want to cover their asses.
NT
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wrote:

I've seen a few personally and heard of many more. Worst I know of was not in a domestic property but a large office building. This was caught before it collapsed but it cost 500k to put right.
The links below give a reasonable idea of the sort of bracing I would expect to see in a normal trussed rafter roof to a house. http://www.wyckham-blackwell.co.uk/trbrace.htm http://www.stalbridge-timber.co.uk/bracing_guide.htm
Jon
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Thanks for all your advice. I have taken some pictures as best I can of the current bracing in the loft. These are at:
http://www.geocities.com/thunder_tank /
My roof has the typical W shaped setup.
The first two show diagonal bracing. The apex of the bracing is in the middle of the roof slope at the top. This is present on both roof sides. Each slope that forms the bracing does not go right to the corner of the loft space, I have tried to show this on the picture with the red arrow. There is probably a 1.5 meter gap between where the brace starts and the end of the roof, on both sides of the brace and both sides of the roof.
The third picture I think shows horizontal bracing, this does not go the full length of the roof space. I would say is covers 75% of the length of the roof.
There does not appear to be any other form of bracing.
Any comments would be appreciated.
I would also like to lay some loft flooring, this will only be in the middle of the 'W' shape. Currently the floor is made up of rough pieces of chipboard, paintings (its true..) and off cuts of wood. Most are nailed to the joists.
I want to pull this up and lay some tongue and groove chipboard. The floor will not be walked on often, I will be storing empty cardboard boxes, a few spare carpet tiles and some christmas decorations up there. There is also a suspended shelf in the loft which used to hold a water tank, the tank has been removed, but the shelf remains. I just have boxes on it now.
I just want to check that no additional strengthening work would be needed to do what I have described above.
Thanks,
James

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