Jump to content

Is this rafter detail OK?


MarkH

Recommended Posts

Due to a slight screwup in the design stage the small part of my house requires that the rafters are joined to upstands in order that they tie in with the 40 degree main roof. If anyone could take a look at these photos and tell me if this is ok that'd be much appreciated. My intention beyone what is in the photo is to join each rafter with noggins just above the nail-plate.

 

Incidentally the roof in this section is supported by a (substantial) ridgebeam allowing the rafters to join the wallplate with no collar, we asked for the beam to allow usable headroom in that part - it'll house boiler, sunamp and mvhr.

IMG_20171213_141538.jpg

IMG_20171213_141612.jpg

Link to comment
Share on other sites

Raise the wall plate. If you don't want to lay more blocks, then  a second wall plate above the first wall plate with timber spacers between them.

 

We did this on our garage to raise the roof slightly so it did not cut across a door opening.

 

 

Link to comment
Share on other sites

1 minute ago, Russell griffiths said:

I would say raise the wall plate as well. 

What is going on with those rafters in the second pic?

do you intend bolting them together or something? 

 

They're screwed at the apex but I haven't cut off the surplus yet. 

Link to comment
Share on other sites

20 minutes ago, MarkH said:

 

They're screwed at the apex but I haven't cut off the surplus yet. 

So they are screwed together, do they not have a ridge beam under them? 

This isn’t a detail I have seen before, has this been drawn up like this for you?  

 

Just spotted the big purlin built  into the blockwork. 

Carry on ?

Edited by Russell griffiths
Link to comment
Share on other sites

Some might say I have a bit of OCD so bear with me.

 

Looking again, the REAL problem is that dirt great big steel ridge beam is too far up the roof. It's not in the middle of the small section of roof.

 

Your "fix" is to raise the wall plate on the right hand side. But now when viewed from the gable end it will be obvious the roof is now asymetrical.

 

The proper fix is move the ridge beam. :ph34r: Sorry, I'll get my coat.

Link to comment
Share on other sites

PAD stone is only needed if the load is not supportable on the material as it is, your SE will probably have specified a solution for this (or should have) which may be just brick work or a pad stone - if you have no calculations for the beam's loading on the bricks it would make sense to get it checked, particularly if you are going to move it althoguh it looks about right to my eye, and counting brlocks its 7.5 blocks wide which is 3.75 blocks to the centre and it looks about there to me.

Link to comment
Share on other sites

1 hour ago, MikeSharp01 said:

althoguh it looks about right to my eye, and counting brlocks its 7.5 blocks wide which is 3.75 blocks to the centre and it looks about there to me.

If the beam was in the centre and both sides are the same angle, the front and rear wall plates would be at the same height.

 

I am sure the angles are the same, so that means if the right hand wall plate needs to be higher, then the ridge beam is too far to the right as seen in the picture.

 

Raising the wall plate is no doubt the easiest fix if you can live with it looking odd from the gable end.

 

I accept moving the ridge beam is not trivial.:ph34r:

Link to comment
Share on other sites

On 12/13/2017 at 17:41, ProDave said:

 

Looking again, the REAL problem is that dirt great big steel ridge beam is too far up the roof. It's not in the middle of the small section of roof.

 

 

No, the ridge beam appearing off center is an optical illusion - a few people have fallen for it in real life too. The beam is precisely in the center of the small section of roof and therefore the wall plate on both sides needs to come up the same amount.

 

Padstones - because the walls are dense block on flat no padstone was specified.

 

Purlins not-plumb - they're well oversized from spec so deflection shouldn't be an issue. 

 

 

Link to comment
Share on other sites

  • 3 weeks later...

Hi.You need to raise the plate both sides in masonry ideally and birds mouth the rafter into the ridge correctly. max 1/3rd rafter depth measured at 90deg not the plumb cut. to do this and keep the pitch the same you will need a thicker plate on the steel as its too low if no bird mouth in photo. Dont forget to do the same on the wall plate. you also have no rafter tail so no soffit overhang this may be correct in this case but just check. if you want no soffit raise the wall plate so you get a full seat cut . quicker and easier for you.

 

Link to comment
Share on other sites

23 minutes ago, albert said:

Hi.You need to raise the plate both sides in masonry ideally and birds mouth the rafter into the ridge correctly. max 1/3rd rafter depth measured at 90deg not the plumb cut. to do this and keep the pitch the same you will need a thicker plate on the steel as its too low if no bird mouth in photo. Dont forget to do the same on the wall plate. you also have no rafter tail so no soffit overhang this may be correct in this case but just check. if you want no soffit raise the wall plate so you get a full seat cut . quicker and easier for you.

 

Think the compos gone off now!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...