Repair cracking roof strut

revengep8nt14

Hi, this roof strut is cracking as pictured. What's the best way to sister supports onto the strut to avoid further cracking?

WIAWSNB

That's a vertical strut, as shown in the pic?

In which case, I'm pretty sure no reinforcement is required. 

But others will advise better. 

Mr.Generous

If worried put a few screws threw it to hold it together, all it needs. 

stuart45

It looks vertical because of how the photo was taken. Looks like one of the web members of a Fink trussed rafter. It will be either in tension or compression, so these parts can crack. Repairs to trussed rafters are above my pay grade.

Section62

Mr.Generous said:

If worried put a few screws threw it to hold it together, all it needs. 

Risky, as the screws could easily cause further splitting.

I agree with stuart45.  I wouldn't do anything DIY to it without asking a qualified SE to rule out anything more sinister.

EssexExile

That crack is called a shake and is nothing to worry about.

35har1old

EssexExile said:

That crack is called a shake and is nothing to worry about.

EssexExile said:

That crack is called a shake and is nothing to worry about.

I agree nothing to worry about

WIAWSNB

stuart45 said:

It looks vertical because of how the photo was taken. Looks like one of the web members of a Fink trussed rafter. It will be either in tension or compression, so these parts can crack. Repairs to trussed rafters are above my pay grade.

Such a 'split' would be of more concern if under a bending force. In comp or tension, timber is immensely strong.
I think it is clearly over-spec'd in any case, at least partly to take into account potential 'flaws' like natural shakes and large knots, as one look at the relatively small size of the fixing plates show. 
I personally wouldn't give that 'crack' a moment's concern, but if in any doubt would check it at regular intervals to see if it develops.
Which it won't do.

stuart45

The timber used for trussed rafters isn't really over-spec'd. They're designed to use the minimum timber sizes to keep the cost down. The connector plates are fixed in the factory and repairs on site using a lump hammer don't work as well. 
People sometimes cut pieces off one or 2 of the webs to make room for something, not realizing that unlike a cut roof, every part of a trussed rafter is really important.
When trussed rafters first came over from the USA, builders didn't realise that over there the roofs were boarded over with plywood which added a lot of strength. Some of the roofs here started getting problems with wind racking, so diagonal bracing was introduced.
Many of the older properties don't have the diagonal bracing, so when a house is sold a surveyor will recommend it's a defect. Originally, surveyors were instructed that properties that had stood the test of time without any issues were OK, but in recent years they tend to flag up any without the bracing.

Section62

35har1old said:

EssexExile said:

That crack is called a shake and is nothing to worry about.

EssexExile said:

That crack is called a shake and is nothing to worry about.

I agree nothing to worry about

If it were just a piece of studwork then I'd agree.  But this was supposed to be graded timber used in a structural element... it shouldn't have shakes.

If it has split under load then that is worthy of asking a SE for advice before attempting a DIY repair.

WIAWSNB

stuart45 said:

The timber used for trussed rafters isn't really over-spec'd. They're designed to use the minimum timber sizes to keep the cost down. The connector plates are fixed in the factory and repairs on site using a lump hammer don't work as well. 
People sometimes cut pieces off one or 2 of the webs to make room for something, not realizing that unlike a cut roof, every part of a trussed rafter is really important.
When trussed rafters first came over from the USA, builders didn't realise that over there the roofs were boarded over with plywood which added a lot of strength. Some of the roofs here started getting problems with wind racking, so diagonal bracing was introduced.
Many of the older properties don't have the diagonal bracing, so when a house is sold a surveyor will recommend it's a defect. Originally, surveyors were instructed that properties that had stood the test of time without any issues were OK, but in recent years they tend to flag up any without the bracing.

By 'over-spec'd' I just mean that the size is chosen to take into account expected irregularities. Yes I know it's graded, but it ain't a homogenous material, so chosen size covers these variations. If it were homo, then it would almost certainly be a smaller profile.

However, if that shake appeared after installation, then it bears a SE visit. 

As a non-betting fellow, I'd happily bet on this outcome, tho'.