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sill plate level tolerance

Last Post 23 Jan 2007 09:56 AM by tmsu. 5 Replies.

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gregj

Basic Member

Posts:326

17 Jan 2007 06:27 PM
I understand that it is critical that the sill plate be as level as possible when using SIPs. But at some point one needs to say "done". So how level should the sill plate be in order to have the SIP installation go smoothly?

mmacgowa

Basic Member

Posts:166

19 Jan 2007 06:58 AM
There are a few factors to consider. First is the type of roof. Are you using sticks, SIPs, or trusses? Sticks have the most forgivness but they are cut with from a pattern so they don't have much forgivness either. Next, how complicated is your roof? a flat roof or one with simple gables is goint to be more forgiving then a complicated hip roof with a lot of ridges and valleys. Roofing has less of an effect, but all error will ultimately transfer to the end of the job. Just do the best you can. Keeping the top square is most important. What you end up with is your tolerance, but I would try to get it down to a quarter inch or less if possible.

gregj

Basic Member

Posts:326

19 Jan 2007 01:14 PM
I should have worded my question differently. I meant the sill plate on the foundation wall upon which the floor joists will be set. Or, in the case of the garage, upon which the SIP walls will be set. (Also called a mud plate or mud sill by some.) I'm trying to find out how level the floor deck and garage mud sill need to be to have a pleasant installation experience with the SIP wall panels. I'd rather spend whatever time is needed to level the floor and mud sill than deal with the aggravation of poor fitting SIP walls due to unlevel floor. So how much deviation across say every 20 ft would result in me saying "wow, that was easy" when I install the SIP walls? And how much deviation would result in me saying "that floor was level enough but I wouldn't want it any worse"? And how much would have me saying "never again"? Or maybe the better question is how level do you insist on before you will put on SIP wall panels?

SRS22

New Member

Posts:9

19 Jan 2007 02:23 PM
Having a level sill plate is very important. The tolerance for panels in a 20' run is probably around 1/4". Doesn't leave much room for error does it? A dip in foundation is much easier to overcome than a rise, and doorways will also aid in absorbing foundation inconsistencies. It would also depend on whether you stand/set small or large sections of panel at a time. We preassemble our walls, so an accurate foundation is very important to us. Our foundations are also panelized. That has given us a much more consistent (level) foundation compared to what we get out of poured in place foundations.

vbihomes.com

mmacgowa

Basic Member

Posts:166

20 Jan 2007 08:02 AM
Walls can be adjusted at the spline to stop a stair stepping effect from a sill that is not level. Walls are normally put together as tightly as possible but some factories suggest a gap fro shrinking/swelling effects. But if you are not perpendicular to the foundation, you will start stairstepping. It isn't a big deal if you end up long or short on a run. You add material to the end plate or trim the end to fix wall issues. The issue as I was trying to state before is that everything transfers to the roof, where all of your issues become realized!

tmsu

New Member

Posts:76

23 Jan 2007 09:56 AM
Posted By mmacgowa on 01/20/2007 8:02 AM Walls can be adjusted at the spline to stop a stair stepping effect from a sill that is not level. Walls are normally put together as tightly as possible but some factories suggest a gap fro shrinking/swelling effects. But if you are not perpendicular to the foundation, you will start stairstepping. It isn't a big deal if you end up long or short on a run. You add material to the end plate or trim the end to fix wall issues. The issue as I was trying to state before is that everything transfers to the roof, where all of your issues become realized! Mac is right about the "transference". I found out the bad way with my SIP build. I was pretty level at the sill, however, a header (16') long bumped up one side by about 1/4". I did some "shaving" and called it "close enough". The second floor on that side was now about 3/4". After trying to "shave" some more, I went with close enough again. By the time I put the trusses up (hip roof), I had almost 1.5" of height difference. Fortunately for me, my metal roof guy did a great job "making it work". I am obviously NOT a carpenter and learned a valuable lesson. If I had a do over, I would have taken the time to make sure it was level (or with a 1/16" anyway).