Hi All,
I’m using Garry Katz’s method of laying out the stair stringers for my deck: https://www.thisiscarpentry.com/2010/04/23/solving-porch-problems/
The method basically involves marking the diagonals of each step to avoid cumulative error due to the rounding of the rise to measurable 16ths of an inch.
After laying out a template (wide stairs with PVC decking means I have to cut 10 stringers) and test fitting, I found that the bottom of the stringers was not bearing evenly on my concrete pad. It was resting only on the heel of the stringer (point closest to the deck) and the toe (point furthest) was about 1/16″ too high.
Otherwise, all the riser heights (including bottom and top to the decking) were within a 16th of an inch of where they need to be and the treads were less than a 16th out of level.
All this leads leads me to conclude that this isn’t a mismeasurement issue.
Instead, I think it is another byproduct of the riser height rounding errors (i.e., the stair gauge angle isn’t perfect causign the treads and the heel cut to be slightly out of level).
Is the uneven bearing a problem? If so, what’s the best way to fix it?
Can I safely use shims?
Thanks in advance,
Patrick
Replies
I’d just scribe the concrete angle onto the stringer. 1/16th of an inch off the heel isn’t enough to make too much of a difference. Next time before you make all 10 cut one and hold it up at every stringer location to make sure it’s resting on the concrete properly.
I actually didn't cut any of them yet...only a template made from 1x12 laminated pine.
I was test fitting the template (before cutting any of my 2x12 PT boards) when I noticed the problem.
Thanks for the tip though. I tried it and it worked perfectly. It didn't even mess up my riser heights; because the heel was striking the concrete first, it was lifting the first riser too high and scbribing it brought everything into line.
Thanks again!
-Patrick
Just wondering, did you subtract the tread thickness from the bottom of the stringer?
If not, this would cause that kind of misfit.
Yes I subtracted the tread thickness from the riser.
I supect it's just that the pad is mayve slightly out of level. Might also be rounding error. The true riser heights are a fraction that isn't measurable so the bottom riser gets cut to a measurable height and this could be creating the slight angle different that causes it to bear unevenly.
With the marking the diagonals method, each riser ends up a slightly different height, but all within a 16th of an inch.
Still, primitive's fix worked perfectly so I'm not worried about it anymore.
Next problem is that much of my 2x12 stringer stock has heartwood in it and has developed checks going right through the middle such that the riser/tread triangles are at risk of breaking off.
I'm tempted to fill those cracks with low viscocity epoxy to prevent the triangles from breaking off.
Any suggestions to that problem would also be appreciated!
-Patrick
Good deal on the cuts.
I think the epoxy is probably okay, it will certainly help preserve the wood. I like Abatron for that type of work. Also, I've used screws (long deck or even timber screws) to reinforce those corners. One thing to be aware of is the differential shrinkage if the lumber is overly moist. You may find that over time the outside corners are no longer square. You may need to shim up the front of the treads if this becomes bad enough.
To avoid cumulative error in building stairs, I use blocklayer.com to provide the dimensions, in lieu of using a calculator designed for construction projects. I also recommend Andy Engel's "Building Stairs" book as a great reference for indoor and outdoor stairs...