Position of hip rafter

[Sonnypaul]

Evening all,

I'll try make this my last post for now as I've asked a lot of questions this weekend

We're planning on building a porch with a hipped roof.

The porch will be 1200 out and 3000 across.

We shall be using plain tiles and was wondering should I pitch it at 35 degrees or should I Mimick the house which I think is 38 degrees.

Other question is how do I measure where the hip rafter goes on the house wall, would I measure 1200 across the wall plate to create a 90 degree angle? And put the commons inside of this line?

Hope this makes some kind of sense ..

Thank you everyone

 

[stevethejoiner]

Do some scale drawings. 35 and 38 degrees sounds close, but from across the road, the porch may look odd if pitched differently to the main roof. It may look great, but you will see this on a drawing.

 

[Sonnypaul]

Thank you for that Steve, and thanks for your comment on bedding hip tiles, very helpful mate

 

[noseall]

The hip rafter would sit in the crook created by the last two full (90 degree opposite elevation) commons.

However, on a lean-to you will have the last full common and the wall at 90 degrees to this common. The hip sits in the crook created by the last full common and the wall.

You can use your common pattern rafter on the opposite elevation (i.e. the elevation that is abutting the house wall) to determine the 'going' of the hip. Just drop the birdsmouth into the wall plate and lower into position until the plumb cut reads plumb on the level or when the peak of the plumb cut is level with his mates on the opposite elevation.

In the image below it shows where the position of the first full common (in green), on the return elevation, would be sitting should this be a regular hip roof and not a lean-to.

Hippy

• noseall
• 14 Sep 2015

 

[noseall]

Don't forget to mention your pitch when ordering your bonnets. Not such a big issue with bonnets as opposed to arris hips, but just mention it all the same.

 

[Sonnypaul]

That's brilliant noseall, thank you for the drawing!

Our porch will be a lean to hip roof,

Would I still need that green common rafter against the wall?


Yeh using bonnets not the arris ones,

I'm going with 38 degrees coz that's what the house is

 

[Sonnypaul]

How does this look noseall, have I done this right..

 

[noseall]

How does this look noseall, have I done this right..

No.
The hip must travel all the way to the wall.
The wall itself is serving as the edge of what would be the position of the opposing rafter, so the hip must be central to this. As in my drawing.
The rafter that you are showing abutting the house wall will effectively be a jack rafter with a compound cut on it. This will abut the hip.

Hippy

• noseall
• 14 Sep 2015

 

[noseall]

Would I still need that green common rafter against the wall?

The green rafter is just superimposed. It shows you the position of what would be the opposing elevation common, if you were building a standard hip roof. The dotted line in the second drawing is also the superimposed position of what would be the opposing full common.

Instead of a rafter, you have the house wall. The hip must bisect this junction to be in true plane.

What you will fit against the wall and up to the hip is a jack rafter with a compound cut on the end.

 

[Sonnypaul]

Yes!! Gotcha now, it makes sense now you say that, have to keep it 90 degrees.

Noseall one more question if you wouldn't mind answering for me,

Why do some porch roofs have a little ridge? Maybe like 500mm or so, is it easy to work out if a porch will need a ridge?

Thank you mate.

P.s . I've booked a roof construction course at the BTC in Waddon, down the road from me but my dad and I are doing our porch first hence the reason I'm poking your brains

 

[noseall]

If it is a lean-to hip (and I'm reading the job right), then there will be no ridge. Given the dimensions of a 1.2m out, 3m across and 1.2m return, you will end up with a pair of 1.2m hip ends with a 600mm flat bit between.

 

[noseall]

Have a look at this thread you might find it useful.

 

[Sonnypaul]

Yeh there is no ridge on mine but I'm just saying when I see other porches with a ridge, what dimensions would a porch be to have a ridge?

And also


That 600mm wall plate in-between will only take 1 common because the other 2 commons will be on the wall? That's right isint it.

 

[noseall]

Yeh there is no ridge on mine but I'm just saying when I see other porches with a ridge, what dimensions would a porch be to have a ridge?

Not sure what you mean?

That 600mm wall plate in-between will only take 1 common because the other 2 commons will be on the wall? That's right isint it.

Have I read your job right with my first ..er.."drawing"? If so, you will end up with a pair of commons each at the point where the hip meets the wall. Span tolerances may also mean a third, i.e. one in the middle.

The link to an earlier post I sent you above, should be helpful. The images show the pitching plate (pole plate) at the rafter ends (where a ridge board would nornally be) and not beneath the rafter. This moves the plane of the roof forwards by 50mm. This changes the design of his roof slightly in that the hip rafter now butts up to the crook created by the two opposing end commons.

I prefer to have the pitching plate beneath the rafters so that the rafter ends are touching the wall. It also helps where roof height and upstairs window sills etc are prohibitive.

 

[Sonnypaul]

Evening noseall, yeh I understand everything you said,

What I meant is, if I decided to have a pole plate under the commons will it sit under the commons only and not the hip? Because the hip goes straight to the wall.

So basically I'll have my pole plate under 3 commons