Roof rafters an inch lower at one end - Advice please?

[hammerswinger]

Hi,
I have just noticed today that the rafters at one end of my lean to extension roof are 26mm lower than at the other end, the roof is 9 meters in length.

Let me explain...

I had the roof timbers on my ground floor extension fitted by a joiner about a month ago, the joiner was recommended by the bricklayers that were putting up the shell of the extension for me, apparently they use this joiner quite a bit to do roofs for them.

I haven't felted or tiled the roof before now as I needed access to the bedroom window so it could be renewed and to remove the bathroom and toilet window and alter the brickwork to make this into one window and I didn't want to be clambering all over the new tiles while doing this.

So today I started to fit the soffit & fascia boards ready to felt & tile the roof, I noticed while trying the fascia board in position that at one end of the roof the fascia was 45mm above the end of the rafter (correct for the eaves tile height), and at the other end it was 70mm above, the fascia was level while the measurements were taken.

The rafters are all at the correct height on the ridge plate on the wall of the house and this is level, the problem with the rafters is at the wall plate of the extension wall. The wall plate is level.

Is my only option to lift and pack the rafter on the wall plate? or could I somehow cut a wedge to fit to the top of the low rafters to get the level correct?


Any advice appreciated, Thanks.

 

[digdilem]

Are you sure it's not been done deliberately? Flat roofs usually have a very small fall so you know where the water's going to come off.

Sorry if that's too obvious but it's not clear from your description if it's falling to somewhere not suitable.

 

[hammerswinger]

Hi,
Sorry, the one detail I left out was to mention that it is a pitched roof.


Thanks.

 

[Mw Roofline]

If you get a stringline along the whole lot, about a foot up the rafter, how does it look level-wise?

 

[hammerswinger]

Hi,
Do you mean with the string line set level or just following the rafters?

The 26mm measurement was taken plumb above the outside brickwork, I used a water level to measure this.


Cheers.

 

[joe-90]

If the ridge plate is level and the wall plate is level - how can the rafters not be level? Is the extension out of square or something?

 

[^woody^]

The walls are not parallel, so the rafter level differs

 

[hammerswinger]

I think the birdsmoth cuts have been done wrong, some deeper than others hence the height difference.

Even if the walls weren't parallel (extension out of square) I would have thought that you should be able to get the rafter heights the same?


Cheers.

 

[joe-90]

hammerswinger, Woody is an experienced and qualified surveyor and I'm sure he's seen this type of thing before.

 

[hammerswinger]

hammerswinger, Woody is an experienced and qualified surveyor and I'm sure he's seen this type of thing before.

Hold on there... what's that all about?

All I'm saying is that even if the walls weren't parallel there must be a way to get the rafters all at the same level, I'm not questioning woody's experience I'm just wanting to understand this.




Cheers.

 

[SurreyRoofingEstimator]

standard thing for the levels to be out surely (considering the amount of jobs we go to with the same issue), we even had one that was out and it had a steel frame!!!

 

[hammerswinger]

Hi,
the roof is a low pitch to start with (Tiles at about 17 degrees) so at the end where the rafters are low this is going to cause the tiles to be at a much lower pitch.

Edit....
Just had a better look while dodging the rain showers, the rafters aren't all at the same height above the wall plate on the extension wall, they get lower as they go along, so it looks like for some reason the birdsmouth joints have been cut deeper as the rafters have went along.


Cheers.

 

[joe-90]

Why don't you ask the joiner then?


BTW, is an inch over 9 metres something you really want to worry about?

 

[hammerswinger]

I'm going to, but I want to be sure about what I'm talking about before I do, so I don't get fobbed off.

He's obviously mucked up & in my experience people don't like to admit this.

I can't see him taking the roof down & starting again can you? so I'm trying to find out if there is an easier solution to the problem.

The inch over 9 meters is a problem as the tiles will loose their pitch.


Cheers.

 

[freddiemercurystwin]

An inch over 9m is not that much tbh and the pitch loss is insignificant. Have you done your stringline yet to see what's out? Have you checked the level of the blockwork/wall plate yet? Have you checked the wall is parallel to the existing yet? Its only really a problem if the soffits/fascia/gutter don't work.