What are acceptable tolerances for framing?
I’m building a house for the very first time and as a rank beginner, I’ve made mistakes; currently make mistakes; and will make more mistakes in the future. I’ve been able to fix quite a few of them as I go, but not all of them.
What I’d like to know is just what tolerances I should be shooting for. Knowing that can help me determine when I need to go to extremes to rectify past mistakes and when I can just let it go.
For instance, I’m going to be building a hip roof with rafters. But the four bearing walls are not perfectly square. In each case, the opposite walls are some amount out of parallel. At what point does that become a problem?
Similarly, the top of the walls are not perfectly level. What amount of variance is a problem and what is “good enough”?
Thoughts?
Replies
We target for as close as possible, but I’ve always been told 1/4” when I started. In my contracts I do include allowed tolerances, but it changes from job to job. There are a lot of tricks to building straight, square and etc. There are a lot of framers that assume foundations are square and level. In the days of laser levels etc foundations are being built more true, but forms move and walls are often off. While I do not recommend building out of square etc., you might be alright (depends on how far off you are). Main areas of concern are kitchen and baths. If the walls are out of square too much the cabinets will not install correctly. Also, with a hip roof you will not be able to calculate rafter lengths and will need to use the measure method as calculations only work when square. Walls not being parallel is a big issue for rafters. Depending upon how far off you are you may need to measure every common rafters individually. While this is not really the proper way to build, you can get a structure up that is safe and to the eye appears straight. On remodel projects I often encounter existing walls that are way off and it’s not feasible to move the walls or build new. We can almost always get it looking right to the eye. It all really depends on how far off you are.
A bit of advice if you are a beginner. Do not assume you will be able to figure out how perform a task as you are doing it. Research first and learn how to before you do it. Also, if you are in over your head do not continue to make mistakes. I always feel terrible when I tell DIY customers that I have to rip out all their work. It’s a big hit to the budget and to their pride. If you get to a point where you are unsure of something stop and figure it out before moving to the next step. I’m not trying to discourage you or take the wind out of your sails, just be cautious of making big mistakes. Being on this forum is an indication you are well aware of that already. Good on you for building your own castle with your own hands. Good luck.
Thanks for the thoughtful response!
Yeah, I do obsessively read articles and watch videos on home building. It's almost cliche to say that there's no substitute for experience, though, and I certainly see a vast difference between my theoretical knowledge and my practical abilities. I will often know the mechanics on something (like how to plumb up a wall) but completely miss a fundamental aspect that is simply not worth mentioning to the pros (like WHEN to plumb the wall). That last example is a good one. In all of the many many articles and videos I encountered on framing walls, precisely one of them (by YouTube's "Essential Craftsman") has ever directly addressed the importance of plumbing up the walls immediately before and after raising them and not delaying until later. I can go back and see that literally every video on framing shows them doing just that... but it's never mentioned but rather just assumed and so I completely missed that. I just assumed I would do it all at the same time "later", not realizing how I would lock myself in and make it impossible to do without resorting to a sawzall and a reframing!
My concern isn't really centered on any interior dimensions, though. I'm installing a "service cavity" around the inside of the exterior wall and that will allow me to get pretty plumb and square just by shimming and planing where necessary.
It's the exterior walls that are concerning because the roof is upcoming and knowing how close or far I am from acceptable will suggest what kind of issues I might run into when building the rafters.
As-is, I'm off by 1/4" in the North-South dimension and a strong 1/2" in the East-West dimension. I might be able to plane off a bit of the rim board in the former case and will have to look more closely on what is off in the latter. I don't YET know how variable my wall height is, just that it's visibly variable. The electric hand plane might help in that case, too.
1/4” and 1/2” + is not bad. You’ll be able to gang cut your rafters and they’ll fit. For your rafter span use the median measurement between shortest and longest measurements. This way you are only off 1/4” (+/-) at worst locations. If you are installing trusses just line them up on your longest wall and make sure the wall is straight. You should have a wall brace about every 8 to 10’ to keep the walls straight. Place braces directly on areas that you can tell need pushed or pulled to be straight. Can take braces down once the roof is sheathed.
I would not plane the top plates down, but would add lumber to bring low heights up. Or you could consider shimming up the rafters and ceiling joists individually if you discover only a few are off. Placing a 4’ level on top of a 30’ long wall will not provide you with a true level assessment. Get a laser or builders level (or even a water level) to check to see if corners are level with one another. If you are w/in 1”, you’ll be fine. If you get above that, you may encounter a few problems. Tack a block on top of each corner and string a line (pull tight as you can) between the blocks. Use the string to see how far off you are. Can even measure off of the string to determine size of shims you will need if you only have a few low spots.
Thank you! This is all excellent advice.
That's excellent advice above. All I can add is to consider why a tolerance matters. For example, top plates being out of parallel will affect your roof framing, whether it's rafters or trusses. You can fudge a lot, but it takes more time and may affect things you aren't thinking about yet, such as the width of your soffits. Plumb (in both directions) framing makes hanging doors and windows easier. Stacking your framing helps your HVAC sub and plumber not to hate you. And so on.
Yeah, that's essentially why I was asking. I am still maybe 90% likely to do the roof (and literally everything else) myself but as a thought experiment, I considered hiring out a crew just to do the roof, since it would be MUCH faster and likely much better done. But at what level would they just look at what I had and refuse to even bid, since the tolerances were too bad and it would cause them too much extra work to work around?
And even not including sub-contractors, knowing how much wiggle room I have can inform me to know how much extra work I'm piling on myself in the future!
This is the question you will spend a long time reviewing every time you build something, like revisiting how a game went, what mistakes were costly, what just worked out in the flow, and what you can do next time. I've worked with guys who wanted to build houses like furniture, but I renovated and lived in a house that was almost two hundred years old. When that was built there was no such thing as uniform material,so renovation meant lots of extra cutting and shaping and eyeballing.
As one of my teachers said, aim for perfect and you'll be close enough.
Plus or minus a small Delta