Trusses

[23vc]

Hi
I've got my roof trusses arriving next week for my extension, and I'm praying they are correct as I had a right job working out the exact pitch to match my existing roof on the back. But assuming I've not massively messed up and they are ok, I was planning on doing the following but due to being a novice I'd appreciate any advice or pointers
1. Do not put wall plate on yet
2. Expose the battens at top and bottom of existing roof (take dry verge off and maybe extend the top and bottom batten beyond the barge board just temporarily)
3. Offer up a truss to existing gable end, and sit it below a top and bottom batten of the existing roof to ensure it fits, mark the wall plate height
4. Take the truss down and bed the wall plate at the right height
5. Put the trusses up in the recommended way going by the instructions that they'll hopefully come with

The front face of the roof is less critical as it will sit below as the wall is set back

Cheers
John

 

[^woody^]

That's messing about.

Put the plates on and strap them down, before lifting the trusses up.

Unless you got the trusses from IKEA, they don't come with instructions.

 

[23vc]

Cheers. My worry with setting the wall plate first is if things don't line up exactly on the roof that I've got to match then I've got zero possibility of any adjustments
Yeah probably got that wrong about the instructions, not so worried about all the bracing as I know I can work it out, more worried about the pitch being slightly out

 

[^woody^]

Surely you know how high the trusses are, so can work out where the wall plate will be?

 

[23vc]

I do know the height yeah, but I'm just worried (possibly unnecessarily) that even if I got it say half an inch out, it would cock everything up and I'd have to modify the battens or something to make it work.
Don't want one or those roofs you see with a bump

 

[Ian H]

If your wall plate is a meaty one could you notch it if needed where the trusses sit?

Bit like that:

 

[23vc]

I suspect that would be frowned upon... I'd rather get the plate height correct. Anyway yet another new territory, should be fun!

 

[noseall]

Ignore Woody and bed the plate once you have a truss on site. It makes no odds to the plate when it is bedded only that the mortar has cured before you start fixing the trusses. The last thing you want to do is mess about re-bedding a wall plate and the masonry beneath.

 

[^woody^]

I suspect Nosey's Transport are paid daywork and a management fee for every time they move a truss up and down the scaffold.

 

[^woody^]

I'm still at a loss to work how how it is not possible to measure vertically from the bottom of the existing ceiling joists (ie plate height), to the top of the ridge or rafters at their apex, or a simlar measurement from any gable and voilà, there is the truss rise.

Or measure the internal span, and then the rafter angle - which will only ever be one of a few common pitches, and then again behold the truss rise.

Then bed the plate on.

 

[23vc]

OK - I fully appreciate most of this is down to my compete inexperience but this is what's happened so far and any pointers on what I've done wrong from you guys are always appreciated

- First off I measured up, myself, the pitch and ridge height, from outside up on the scaffolding, got the pitch as 32 degrees, and I knew for sure the new wallplate span so I thought I was good
- spoke to truss manufacturer, who was fine until I mentioned I was matching an existing roof, at which point he said I absolutely had to provide all the existing roof measurements, ridge height, span, birdsmouth seat depth etc, in order for it to match
- fair enough I thought so I did all that, but alarm bells were ringing as the measurements I took from inside the loft were giving a steeper pitch (33.5)
- sent them off to him and he sent me back another drawing, saying sign it please
- I did a load more measurements, which consistently pointed towards the existing roof having a shallower 32degree pitch, and due to the fact that the ceiling joists had appeared to sag up to a couple of inches in the middle of the house, and I was measuring the ridge height based on that, seemed to suggest that the method of just measuring the existing roof was not very reliable and was falsely giving a steeper pitch
- phoned truss guy back and asked him to put the pitch back to 32 degrees, at which point he seemed pretty unhappy, informed me that the roof would not match the existing, and told me I was wasting his time. Reluctantly agreed to do it though.
- so now I'm pretty sure I've made the right decision by manually measuring it myself and checking and double checking, and if anything I'd rather they were too shallow a pitch rather than too steep. So fingers crossed I'll be OK.
Not really sure what I should have done differently or why the truss guy thought I was wasting his time, as I'm not that kind of guy and didn't think I was!

 

[^woody^]

Well 32° is a bit non-standard.

 

[23vc]

Hmm. Oh well I'll put this down to experience and I'd rather get it too low a pitch than too high. And to be fair literally every other measurement suggested 32 so I'm still hopeful.

 

[Nige F]

and due to the fact that the ceiling joists had appeared to sag up to a couple of inches in the middle of the house, and I was measuring the ridge height based on that, seemed to suggest that the method of just measuring the existing roof was not very reliable and was falsely giving a steeper pitch
-
Not really sure what I should have done differently or why the truss guy thought I was wasting his time,

The only thing I can suggest (as a total Non - carpenter) is that if the cieling had a visible sag, then a string line across from plate to plate would have been a more accurate start point

 

[23vc]

Agree but massive ceiling binders in the way. As well as the loft being full of the wife's junk