Apr 11, 2011 3:35 pm
I am an owner builder building an extension in double brick ; I completed raising the walls and till now never used any tradesmen; I recently employed a carpenter placing a couple of hip roofs as extension to my home. One of the roofs frame is done. However the new roof top ridge where it intersects the existing roof is offset by a few centimeters , which makes the valleys appear as narrowing as the eye goes up . Also the roof plate is not square. When confronted and asked to undo and reassemble, the carpenter alleges that the defects are within tolerances of the BCA ; I have difficulty to determine how to demonstrate the contrary , particularly , if the roof members are cut all correctly and sized, the BCA would not be able to legislate when it comes to poor workmanship or when the result is unsightedly. What is the way forward for me to get the carpenter to fix?
Re: roof carpentry problems2
Apr 11, 2011 6:29 pm
regards the valleys when the roofer comes to tile/colourbond it all they have to do is keep the valleys straight.the valley the carpenter puts in is after all only a layboard.
if the wall plates are out of square as long as the facia line is cut equal distance then you wont notice anything once its covered.
Re: roof carpentry problems3
Apr 13, 2011 11:23 am
Now, yes, I agree this is one way to "hide" the problems
Note that because the plate is not "squared", the ceiling joists are at an angle and the rafters are also slightly angled instead to being 90 degrees to the side of the plate
There is another problem too; the carpenter was supposed to match eaves of the existing house, but because of lack of planning ( he did not position the plate correctly on the wall and did not cut birdsmouth deep enough), the eaves are between 50 mm to 90 mm larger than the original . His proposal is now to cut down the wall by a few centimeters to get the eaves to join without redoing the roof... I find this deeply disturbing as a solution...
Any suggestions welcome
Re: roof carpentry problems5
Apr 14, 2011 2:03 am
Hi jln. I've got a couple of questions.
Firstly I don't quite understand what you mean by the plate not being squared.
When you build double brick the roof is dictated by the brick work. The 90mm plate sits on 90mm brickwork (typically) so there is no way to "square" anything. If the brickwork isn't square then the wall plates wont be square.
The eave size is also dictated by the brickwork. You can make small changes by adjusting the birdsmouth depth but you are still limited.
Can you post a picture so we can understand what it is you are talking about. It's a little hard to follow exactly how the new roof is incorrect.
It's worth remembering that renovations can be very hard to match up. The existing roof may be out and the new roof correct.
As Darrell mentioned roofies are often not the most careful of tradies, but once the roof cover is on you'd never know.
Accessible Carpentry & Cabinets
Re: roof carpentry problems6
Apr 14, 2011 4:49 pm
hello All, Chippy,
Ok. This is the classic case of an extension being built and abutting against an existing hip roof. See pics at my blog ; One plate is essentially perpendicular to the plate of the existing roof; While I have to admit the walls are not perfectly parallel or at right angle ( may be an error of 20 mm over a length of 5.5 meters), there is nothing in the wall that caused a variation of about 37 mm between 2 parallel length of the plates. The walls are 110 mm width , the roof plate is 90 mm wide so there is space to play with the plate to square. The difference of length between parallel plates means that because the joists have been spaced from the end , they are a bit cross. So the joists and the rafters are all a bit angled to the plates they sit on which may be the cause of the displacement of the main ridge where it intersects with the existing hip roof.
The size of the eaves is dictated by : 1/ the position of the roof plate on the wall. The wall is 110mm and the plate is 90 mm so there is a bit of movement we can control the plate to be closer to the inside.2/ The depth of the birdsmouth ; this can be up to 1/3 of the rafters thickness , in such a way that for every cm of extra depth generates about twice the narrowing of the eaves . (Angle of the roof is 26,62 degrees). The current birdsmouth varies from 15 mm to 25 mm while it could have gone to 30 mm . The eaves currently are not all equal in size, which indicate some other problem that I have difficulty to pinpoint . I would like to know what could cause the eaves in one point to be 650 mm where it is between 610 and 620 mm elsewhere; the size they should actually be is 570 mm from the bare external wall.
I also do not like the idea of cutting my wall for "fixing" poor planning ... Looks like that is to save him time?
I placed pics at the following URL http://buildingmyextension.blogspot.com ... cross.html
Ah yes, another thing; the existing house is about 55 years old and the guys who built it knew what they were doing and they had very few tools; their work was fine ; the only issue I found with their work is that the bellcast is a bit low ; surely if they could do it, it should be possible for a new carpenter to do at least the same ....
Thanks for any suggestions
Re: roof carpentry problems7
Apr 15, 2011 6:12 am
if the brickwork isnt square then no matter if the wall plate was fitted square your eaves would still be out,the brickwork has to be good tom start.
you cannot adjust the depths of birdsmouths,you cut 1 pattern jack rafter and use that for all cuts otherwise the roof would run out and have humps and dips in it.i have cut a tapering roof where all the birdsmouths reduced along the roof gradually but is a very time consuming thing to do as each rafter has to be measured and cut individually.
without seeing the job 1st habd its very hard to see where he went wrong but if its wrong from the start then theres no way to fix it other than to pull it down and start again.
cutting walls isnt an option thats just pure madness on his behalf
Re: roof carpentry problems8
Apr 15, 2011 10:42 am
While I agree that if the brickwork is not perfect the eaves will not be perfect, the variations on the eaves could no be more than 20 mm at a maximum, certainly not 90 mm . But a square plate would certainly ensure that the roof is correctly mounted.
As for the birdsmouth , I have suggested that all of them be cut as deep as is authorized by the code , that is 1/3rd for all of the rafters; If not all of them the same depth , you would not get a plane surface to nail the roofing battens.
I am glad to hear that cutting down the wall is madness as it will not fix the issue of the roof being skewed
All this is simply a waste of my time. I was supposed to hang the gutters and lay the roof battens and tile it as soon as the frame was placed .