Repair cracking roof strut

stuart45

I didn't notice the rafters.

revengep8nt14

Section62 said:

revengep8nt14 said:

Cracked web section is the first bit of timber on the left.

It looks like there 6x2 rafters sistered onto the original rafters of the truss - I've never seen anything like that as an original build (the truss should have been specified/designed with a larger section rafter if necessary) which possibly means there was either a problem with the trusses, or else the roof has been modified in some way at a later date.

Can you post a picture of the outside of this section of roof, for context.  Has the house been extended or had solar panels added?  And is the roof original to the house, or has it been re-roofed? (the trusses and membrane look much newer than the brickwork)

Good eye. The house was built on an existing terrace, the brick is the shared wall. Everything else looks solid, I've been through the rest of the structure and this is the only area that's cracked.

Original roof, no solar panels.

WIAWSNB

Age of terrace? And are you 100% sure the roof covering hasn't been changed?

I hadn't noticed these additional rafters either, and they are really unusual. 

Do you know who the builder was? Are they still in existence? 

Do you know if your neighbouring roofs are also like this? 

Could a BCO - under guidance from an SE - have possibly insisted on this at the time of build, say if the builder was changing the roof covering to a heavier type than originally specified for this terrace? 

revengep8nt14

The roof covering hasn't been altered. I've been up and taken some more pics, it seems to me like the pitching has been altered which is the reason for the the extra rafters? Either way it doesn't look great. Looks like it's been fixed with nails to the main rafters.

revengep8nt14

So the extra rafters are not sistering or supporting the main rafters at all? I don't know who the builders were. Property is over 10 years old.

stuart45

They must have measured the roof incorrectly and got trussed rafters that didn't line up with next door's roof, so they have just added more rafters instead of getting new trussed rafters.

revengep8nt14

stuart45 said:

They must have measured the roof incorrectly and got trussed rafters that didn't line up with next door's roof, so they have just added more rafters instead of getting new trussed rafters.

Yes, albeit a bodge job. Nails sticking out everywhere which is not helping the splits in the struts.

Section62

revengep8nt14 said:

So the extra rafters are not sistering or supporting the main rafters at all? I don't know who the builders were. Property is over 10 years old.

Did you get a survey done when you purchased?  Did they go in the loft?

My guess is someone messed up when specifying the trusses, and when they got to installation they found the roof didn't match up with the existing building next door, so had to do a bodge.  Or, much less likely, they had some trusses from another job and thought it was Ok to use them with some modification.

Hopefully they consulted a SE before going ahead, but I have some doubts as putting the additional rafters to the side of the trusses will generate eccentric loading, and the possiblity of introducing forces (including bending) the truss wasn't necessarily designed to take.  If these were firrings on top of the rafter that would be less of a concern.

My own view remains the same, before doing anything I'd want to have a SE take a look and comment on the arrangement and possible defects with the trusses.  This isn't to say the roof is necessarily in imminent danger of collapse, but a surveyor looking in your loft when you come to sell might flag these issues up and cause you problems.

I'd also comment that there appears to be a tapering gap between the end of the two rafters of the truss in your latest pictures.  This could be as it was made, but normally members in compression would be cut so the ends are bearing over their full surface area - i.e. cut 'square', or at the correct angle.  Tapering gaps between members which are supposed to be in contact over their full surface area could be a sign of movement, if not poor workmanship or damage in transit/installation.

Section62

revengep8nt14 said:

stuart45 said:

They must have measured the roof incorrectly and got trussed rafters that didn't line up with next door's roof, so they have just added more rafters instead of getting new trussed rafters.

Yes, albeit a bodge job. Nails sticking out everywhere which is not helping the splits in the struts.

Can you see what happens to the additional rafters at the bottom, where they meet the wall plate?

stuart45

If it was my house, I'd speak to the truss manufacturers. They engineer the trusses to specific factors and could tell you how this set up is likely to affect the loading.