Framing rafters for velux??

[Sonnypaul]

Hi everyone need a little advise on a job coming up, I do a lot of the interior carpentry I.e doors and stud work but we have a rear extension coming up and there is a pitched roof.

Basically there's 3 things I need clearing up?

1. Next door already have an extension and we have arranged a party wall agreement to build of there wall, so no need to have a footing along the side if that makes sence. We're basically going to be joining on to there roof so all the tiles follow suit. What's the best way to get the pitch of next doors roof.
I don't know if they birdmouthed there timbers and don't know the exact height of there finished blockwork.

2. The client wants 2 veluxs aswell and I have no trouble fitting them but have only installed them on existing roofs, basically what I need to know is have I got to frame the veluxs to suit the tiles or can I just frame them wherever?

3. When I start constructing the roof what's the best way to square the first timber. I'm thinking if it's not square then the veluxs won't be parallel to the tiles.

Just got confused reading this back to myself so hope you guys can understand

Thank u and would appreciate any comments

 

[noseall]

1. Next door already have an extension and we have arranged a party wall agreement to build of there wall, so no need to have a footing along the side if that makes sence. We're basically going to be joining on to there roof so all the tiles follow suit. What's the best way to get the pitch of next doors roof.
I don't know if they birdmouthed there timbers and don't know the exact height of there finished blockwork.

When you get up to roof height, expose their rafters and drop a level (strike a vertical line) and then set a bevel to the line, then take the bevel to a compound saw. If you have the neighbours roof tiles as a finished parameter or datum then your roof timber thickness and subsequent birds-mouth will dictate the wall plate and finished block-work height and not the other way around.

We would likely work out the pitch, decide on the birds-mouth depth, dummy up a rafter complete with b/m along with a short piece of wall plate fixed into the b/m then fit this in place to show where the brickies need to finish.
Funny thing is, I am the bricky also.

2. The client wants 2 veluxs aswell and I have no trouble fitting them but have only installed them on existing roofs, basically what I need to know is have I got to frame the veluxs to suit the tiles or can I just frame them wherever?

You set the Velux according to the tiles not the tiles according to the Velux.

The bottom of the Velux is set 80mm up from the top edge of the final course of tiles, wherever that course may be.

We even go so far as leaving any framing until we have jiggled and shoved the Velux about until we have decent side tile cuts also.

3. When I start constructing the roof what's the best way to square the first timber. I'm thinking if it's not square then the veluxs won't be parallel to the tiles.

You can set the Velux parallel to whatever irrespective of whether the rafters are parallel provided you allow enough room when trimming out. If in doubt use a 1200mm ally builders square (square off the wall plate) to set your first rafter. don't forget, your Velux sits above any rafter level framing and is set on a roofing batten that is 80mm up from the roof tile course and parallel to the roof tiles.

 

[Sonnypaul]

1. Next door already have an extension and we have arranged a party wall agreement to build of there wall, so no need to have a footing along the side if that makes sence. We're basically going to be joining on to there roof so all the tiles follow suit. What's the best way to get the pitch of next doors roof.
I don't know if they birdmouthed there timbers and don't know the exact height of there finished blockwork.

When you get up to roof height, expose their rafters and drop a level (strike a vertical line) and then set a bevel to the line, then take the bevel to a compound saw. If you have the neighbours roof tiles as a finished parameter or datum then your roof timber thickness and subsequent birds-mouth will dictate the wall plate and finished block-work height and not the other way around.

We would likely work out the pitch, decide on the birds-mouth depth, dummy up a rafter complete with b/m along with a short piece of wall plate fixed into the b/m then fit this in place to show where the brickies need to finish.
Funny thing is, I am the bricky also.

2. The client wants 2 veluxs aswell and I have no trouble fitting them but have only installed them on existing roofs, basically what I need to know is have I got to frame the veluxs to suit the tiles or can I just frame them wherever?

You set the Velux according to the tiles not the tiles according to the Velux.

The bottom of the Velux is set 80mm up from the top edge of the final course of tiles, wherever that course may be.

We even go so far as leaving any framing until we have jiggled and shoved the Velux about until we have decent side tile cuts also.

3. When I start constructing the roof what's the best way to square the first timber. I'm thinking if it's not square then the veluxs won't be parallel to the tiles.

You can set the Velux parallel to whatever irrespective of whether the rafters are parallel provided you allow enough room when trimming out. If in doubt use a 1200mm ally builders square (square off the wall plate) to set your first rafter. don't forget, your Velux sits above any rafter level framing and is set on a roofing batten that is 80mm up from the roof tile course and parallel to the roof tiles.

Thank you noseall that was really helpful.

So if i just space my common rafters to suit the velux openings but not fit the trimmers until i start fitting the batterns?

What im trying to gain is to run my veluxs in line with next doors extension.

The working drawings say to fix the top rafters with jiffy hangers off the pole plate but doesnt say how to fix the bottom, i know birdmouthing is the common way of doing it but could i not just strap them or use jiffy hangers like the top?

cheers noseall

 

[noseall]

i know birdmouthing is the common way of doing it but could i not just strap them or use jiffy hangers like the top?

Birdsmouthing is the better way. It secures the rafter seat and locks everything in place including the wall plate itself.

Once you have made a pattern rafter the rest are easy.

Just make sure you try the pattern rafter in various locations along the wall in case there are any bulges or dips in the wall.

 

[Sonnypaul]

i know birdmouthing is the common way of doing it but could i not just strap them or use jiffy hangers like the top?

Birdsmouthing is the better way. It secures the rafter seat and locks everything in place including the wall plate itself.

Once you have made a pattern rafter the rest are easy.

Just make sure you try the pattern rafter in various locations along the wall in case there are any bulges or dips in the wall.

Gotcha!

The wall construction is 215mm block work so will the 4x2 wall plate sit on the outer edge?

Really appreciate the help noseall.

we had another chippie with us for about 10 years and he left last year and i was always inside doing the internal carpentry and he was doing the outside bits like the roofs etc thats why i like to do my research and make sure i dont turn up scratching my head lol.

 

[noseall]

The plate usually sits on the inner 105mm.

Strapping becomes difficult when you locate the plate on the outer 105mm.