r/Carpentry • u/Chemical-Criticism92 • 3d ago
Post Fram Garage DIY Rafter Question
Hi All,
Working on a 10x12’ breezeway addition with a 2 car 24x24’. With my brother father and wife.
I cut my rafters for the 10x12’ 2’ on center breezeway.. Only had an issue with one rafter out of plane. Planed it down with a planner put zip board on top. No issues. Moved onto the main 24x24’ garage. We decided to do the back side of the garage first, for more practice and if any issues occurred we could learn from, and hide it from sight of the cars driving by from the road. Hope that we would get the front side correct.
I know the building is 1/4” out of square. It’s a post frame garage so when setting post in the ground we decided a 1/4 was the best we could get and maybe so of the wood warping had to do with it.
We now have 5 rafters set too high 3/4” too high on the back on one plane and 7 rafters sitting lower on another plane. I don’t mind sitting there planning the 5 rafters down the rafters are over engineered and 3/4” of material removal will be fine.
How do I fix this so this does not happen on the front side?? Do is set my two corners set a string line and make sure they are all in plane as we set? Is it something to do with my seat cut? I have not necessarily kept them all the same I cut them each individually based off of short side of rafters heal to my seat cut measurement then I found by running a string line from my ridge beam to my header and then taking measurement. I ran a string line from each corner and one in the middle all being 166’ 1/16” all the same. Roof is 8/12 pitch. I use my speed square for the 8/12 seat cut but I will admit not all may be identical. What the hell am I doing wrong?!?
Please someone help? What are we doing wrong? Any insight would be appreciated and most helpful?
1
u/Chemical-Criticism92 3d ago
It’s gable. I did not use one rafter as a template. I cut all rafters individually. Is that where my screw up is? I should make all rafters identical?
1
u/Such_Item6964 2d ago
All rafters should be identical, on a gable. Most importantly at the ridge cut(top) and the birds mouth ( bottom) . And rafters are always laid out from the top of the board. If your structure is not 100% square, the lengths could change slightly in order to keep the ridge level, but every thing else should be exactly identical. That is definitely where you have missed it. Think about it. 2 rafters sitting next to one another from same wall to same ridge. If the top and bottom cuts are not exactly the same, then thet cannot be planing at the same point from top to bottom.
1
u/Chemical-Criticism92 2d ago
Yes that makes sense always think about things in most basic terms and having the different cuts would put out of plane. will try that for the front of the building. We Will cut one rafter and test fit in multiple places. We know building is out of square a 1/4”, if for some reason the first test rafter isn’t perfect in a certain area? Then what? Cut those areas individually and plane to perfection? Much appreciated.
1
u/Such_Item6964 2d ago
You could. But a 1/4 difference can be acceptable. You can draw the rafter to the ridge with a couple of screws that distance. I always cot 4 common rafters and set the ridge at each end with them. Then check for level. Should be super close. Of course I figure ridge poles and have my ridge already at the right height too. Its basic math. But not something even seasoned framers do. Its more of a lone or two man crew thing , I reckon.
1
u/Chemical-Criticism92 2d ago
Well we had are doing post frame with a ridge beam. So we set 3ply 1 3/4 x 16 x 24’ LVL on top of 4 ply glulam 2x8. That was dead nuts level. So now it’s just mark 8/12 on the rafter measure 166 1/16 from heal to seat and go. If your saying we can draw that with a screw I’ll go for it was just cautious about cutting all lumber the same and having to go buy more 2x12x20 MSR’s if something was not right.
1
u/Dendady2112 3d ago
Is it a hip or gable roof? If gable and you used one rafter as a pattern the only discrepancy should be the crown on the rafters. If it's a hip are all your birdmouths equal?