Extending siding over basement wall
I’m building into a mild slope, so on one long face my ground level will be about 3. 5 ft above exterior grade. We’ve got a door on that low side and I don’t want to leave exposed concrete running mid-door height. I also don’t want to drop the concrete on that side and have to balloon frame or build a very short knee wall.
I assume this happens often but I can’t find much in terms of detailing to extend my siding down over the concrete.
My thoughts are to do as follows:
– finish my envelope as if I am not extending the siding, i.e. end everything on the concrete wall and do all base treatments in terms of flashings, sealing, etc.
– Provide p/t nailers to the face of concrete wall and apply the siding to the nailers. Essentially the siding at the concrete wall is a little strip of rainscreen. Any bulk water that gets there would be completely free to run out and I’ll hold it off the ground 6″ to 8″
Any problem with doing this? I don’t love how I’m concealing my base from view to spot any future problems (water, bugs, rot, etc) but other than that am I creating any issues?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Hi Nat.
I'd like to see a photo or drawing to get a better picture of what you are describing, but from your post I think what you are proposing is fine.
I assume that you'll be insulating the concrete on the inside, but one thing that you can consider is adding some rigid insulation outside of the concrete. If this helps you get the siding over the concrete out to the plane of the siding of the wood-framed wall above, it comes with a thermal benefit. I did this on a walkout basement situation and it worked great.
Thanks, Brian. Yes, insulating the concrete basement wall on the inside. I'm still up in the air on the overall above grade wall assembly but whichever way it goes the general idea for this would stay the same (dimensions may vary based on wall system/ext insulation etc).
See attached very rough preliminary sketch. It seems like it would be a good idea to terminate and flash the sheathing to concrete wall boundary as I would everywhere else. Then the lower portion is a standalone screen that is detached and in no way affects my typical base sealing/detailing (other than concealing it). You'd see a discontinuity in the sheathing and the upper flashing poking out but better than 3.5ft of concrete wall. Does this make sense? Am I creating any problems for myself with this?
Nat,
It's definitely a good idea to separate the two levels of siding with flashing - if for no other reason than that the chances of the framing above and the concrete wall being exactly co-planar everywhere are pretty slim.
You may want to re-think what flashing you use there. Not providing any ventilation makes the rain-screen gap less effective. I would put a solid flashing over the lower-siding, but 3/4" up I'd put a perforated J flashing over the base of the upper-siding to allow air movement..
Thanks, Malcolm. Good call. I wasn't aware of the perf j-flashing but read about it and get it now.
I'm not sure what that rainscreen gap will be so that will affect the flashing. I am looking at the rolled products such as home slicker vs the furring strips. My test with all these details is if I can imagine diy'ing it and the rolled products feel much dumber (in a good way) and therefore I lean in that direction. The only negative reviews/cons that I've found is relative cost, although I'm imagining you may get some credit on the labor side. Any thoughts on downsides to using a rolled product vs furring strips?
Hi Nat.
I think your details look good and I second Malcolm's concern to make sure that you have good venting at the bottom of the rainscreen.
Nat,
The effectiveness of rain-screens varies by how well they do the functions we include them for. At the bottom of the list would be wrinkled WRBs, then mesh, going up to the top which would be a deep battened cavity vented top and bottom.
How effective you need the rain-screen to be depends on climate, and how reliant the walls are on drying to the outside. In most cases mesh is sufficient.
Thanks, Brian. Yes, I probably have a lot of other things to catch in there as well - I just wanted to make sure the general idea of siding over the concrete wasn't an issue I was missing.