Minimum gap between roof truss and 2-storey wall.

[epsilonGreedy]

I have a small single story roof that abuts to the main two storey part of the house. The ridge runs out at a right angle.

 

I assume it would be bad practice to position the final truss tight and side-on to the two storey wall? What sort of gap is recommended? The roof cover is slate hence the finishing of the abutment will be traditional lead soakers and flashing. 

[nod]

Normally jam an off cut of 3x2

leaving a 50 mill gap If you butt it up tight You May have trouble plumbing the truss

[nod]

  On 20/10/2020 at 17:49, nod said:

Normally jam an off cut of 3x2

leaving a 50 mill gap If you butt it up tight You May have trouble plumbing the truss

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[epsilonGreedy]

@nod The picture helps a lot.

 

Is that a metal strap spanning across the first two trusses then fixed to the blocks?

[Gus Potter]

I think epislon is having a look at how the wall is tied in at ceiling level so is asking a good question.

 

Take, if you can a photo of the whole length of the ceiling where it meets the wall from both above and below. Take some close up ones of any steel straps, any fixings and some panoramic ones so the likes of epilon can see the whole roof structure.

[nod]

  On 21/10/2020 at 21:34, epsilonGreedy said:

@nod The picture helps a lot.

 

Is that a metal strap spanning across the first two trusses then fixed to the blocks?

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It is a wall plate strap 1500 in length Spanning three trusses 

the l hooked into the cavity Then built in 

Four on either pitch

8 in total 

[nod]

  On 21/10/2020 at 21:48, nod said:

It is a wall plate strap 1500 in length Spanning three trusses 

the l hooked into the cavity Then built in 

Four on either pitch

8 in total 

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  On 21/10/2020 at 21:45, Gus Potter said:

I think epislon is having a look at how the wall is tied in at ceiling level so is asking a good question.

 

Take, if you can a photo of the whole length of the ceiling where it meets the wall from both above and below. Take some close up ones of any steel straps, any fixings and some panoramic ones so the likes of epilon can see the whole roof structure.

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Only a garage Which I built ours and nest doors with a cavity wall before we started the main house 

I kept things pretty plumb But keeping the trusses off the wall gave me a little wiggle room 

Hope this helps 

 

[Gus Potter]

Good photos Nod.

 

You can see from Nod's photos how the metal straps & noggings (dwangs in Scotland) are installed so that when the wind sucks out the gable wall the load is resisted by the trusses, roof structure acting together. The roof acts like a deep beam and this holds the gable wall in place. There is easy to find guidance on this from say the NHBC details online.

 

The same rules apply at ceiling level unless the wall has been designed on the basis of floor to ridge height. I think Epsilon has spotted this.

 

Good example Nod of a job well done.

 

You can see from Nod's photos how the diagonal wind bracing has been carefully cut where it meets the blockwork. By doing this Nod has ensured that the end distance for the nails has been maintained..in other words if a nail is too close to the end or edge of a timber it is no good.

 

You can also see how Nod has placed the bracing close to the node points of the trusses as per good practice etc.

[Oz07]

On the job I'm on they're fitting timber spandrel panels and face fixing the strap to the inside of the panels. The inspector comes round and pulls them up for not putting enough fixings in the length of the strap but somehow missing the point that even if there's a million fixings in the strap it's only relying on 2 or 3 screws into the studs on the spamdrel panel. These screws are also relying on the friction from the thread ie not in shear. Its rough as a badgers arse. 

[epsilonGreedy]

  On 21/10/2020 at 22:26, Gus Potter said:

You can see from Nod's photos how the metal straps & noggings (dwangs in Scotland) are installed so that when the wind sucks out the gable wall the load is resisted by the trusses, roof structure acting together. The roof acts like a deep beam and this holds the gable wall in place.

 

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The more I get into self build I appreciate how much mutual support there is between each section of a house. In my case the upper storey is not a gable, it is the main two storey part of the house, so perhaps the house wall braces the the small section of roof on the 3.8m x 2.6m single storey roof. The hip end should help as well.

 

My conclusion from this thread is that there is little wood to masonry connection or support at the roof abutment apart from a few 3x2 jams mentioned in the first reply. The bracing across the trusses particularly the diagonals provides the lateral truss stability plus the hip end. The metal straps in my case will be screwed into the main wall and probably won't add much unless some fancy technique is used to attach the strap end to the blockwork.

[epsilonGreedy]

  On 21/10/2020 at 22:26, Gus Potter said:

You can see from Nod's photos how the diagonal wind bracing has been carefully cut where it meets the blockwork. By doing this Nod has ensured that the end distance for the nails has been maintained..in other words if a nail is too close to the end or edge of a timber it is no good.

 

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I just want to check I understand this advice. Looking at the photos the diagonal is cut just beyond the truss fixing point so the nail is not running through the bitter end of the wood where it is prone to splintering?

[Oz07]

Build your straps into the cavity at top of ceiling chord height. The straps are made to resist bending straight. 

[Oz07]

This is what I mean. They're getting signed off so it must pass but personally I think it's crap. Other sites they make you hook over the panel. Also pictured the dorner framing rough as a badgers arse I had to go alter a bit for the roofers today I couldn't put my name to work like this. 750k house n all.