Should Ties Be Removed?
My foundation contractor doesn’t think the ties used to hold up the rebar inside of the forms which are now sticking out of the foundation walls need to be removed and in fact he said that they would be useful for holding rigid insulation in place. The ties are roughly two feet apart and there are three levels of them around the perimeter of the foundation. This is a slab foundation, so the ties will be below grade, along with the insulation.
My gut tells me that it’s a bad idea to use the ties to hold the insulation in place. While it’s a lot more work, It makes more logical sense to knock them off, grind them down (as well as the bumps from the pour) so that the insulation can be glued properly to the walls. Also considering weatherproofing the walls, but that may be overkill.
Anyone out there have similar experience?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
They should all be taken out and cover the wall with waterproofing, otherwise they'll rust and create a pathway to moisture on the inside in the long run. He's just avoiding to do the work.
I agree, you need a smooth wall to install the rigid foam.
The type of forms we use down here, the aluminum tie stubs are square with a hole for the rebar to pass thru and support the forms. I like to use those square stubs as foundation bolt washers.
Armando,
We use a version of those that takes a rectangular bar that we rent for each job. I like that they are easy to break off. I hate how sharp they are before you do that. My knuckles have several deep scars from them.
Armando, what would you recommend as the best method(s) to break them off? I used 2lb short handled sledge and the one I hammered didn't break after going back and forth several times. I'm afraid that the more I hammer them, the more of a bigger hole it will make as it goes back and forth. I've got a grinder with a diamond cutting wheel. It's a lot of cutting to do, but that might be a clean way to do it.
scottwoodward,
Those are odd snap-ties. Usually they have a plastic disc embedded in the form and stick out about 6". They are removed by putting a small pipe over them, bending the tie, and then rotating.
Some of yours seem to have concrete protruding too. Not sure there is any easy way to remove them short of a grinding disc now.
@Scott - There are many types of ties, but I've never seen the type of tie you have, so I can't help you, sorry. Maybe some other person here has used them and can tell you.
Armando,
Up here in seismic-land we use large square anchor bolt washers.
@Malcolm - The foundation guys use a small crowbar with a custom split end and twist them. I have them collected, as those tie ends make the best washer for foundation bolts.
Thanks guys. I think I'll end up cutting them off with the grinder. I thought about using bolt cutters too.
I would make sure to use some liquid flashing in every cut-off tie to prevent rusting, unless your are waterproofing right away.
BTW, if you can't make the foundation guy remove those tie ends, I would deduct your labor out of his bill.
I think the only option for getting those off is a small angle grinder. That's probably part of the reason the contractor doesn't want to take them off -- it's a decent amount of work to do. It needs to be done though. I absolutely agree with Armando that those tie ends will rot out over time, and that will leave a moisture path into the groundation through the damp proofing. One of the major contributors to concrete failure in the commerical world is when enough concrete is chipped off to expose some embedded rebar. Once that steel rebar is exposed to the weather, it starts to rust -- and that rust goes up the rebar into the concrete and starts to fracture the concrete. You eventually have failure of the concrete itself.
If they give you the line about "they'll hold rigid insulation in place", tell them you plan to just use adhesive for that purpose.
Bill
Quick update. Taking matters into my own hands, I purchased a Makita angle grinder, a Rigid diamond metal cutter and two Makita diamond attachments to smooth out the bumpy concrete. Made rather quick work of it. It only took me about three hours to grind off the ties and smooth out the walls. The Rigid diamond metal cutter works very well. I cut half or three quarters of the way through and then a few knocks with a ball peen hammer and the ties came right off. I could do a vertical row of four of them in about a minute or two. The grinder is a great addition to the tool collection and has already paid for itself.
See photos from just a bit ago. Let me know if you guys think it passes muster. In the second photo, you can see a seam I had not yet smoothed out. Good before and after.
Nice work!
Looks great.
1000% better
you are the man ..
Thanks everyone for your help and confirmation. Putting on the liquid flashing tomorrow. Looking forward to getting the insulation on next week. Really hard to find EPS insulation, so I'm going with the newly formulated more eco-friendly Dow XPS Scoreboard.
Happy New Year!
As a counterpoint, I own a house built in 1976 where the ties were never removed. They haven't rusted through. They are a handy spot to hang things like garden hoses.
Interesting that the ones on your foundation haven't rusted through in all those years. What part of the country are you in? Do you suppose the ties from that era were of higher quality steel or some other material? I noticed that the bottom ties on my foundation walls were already completely covered with rust since they've been exposed to rain and snow for the last three weeks. With the weather here in New England, I imagine it would just be a matter of time before those and perhaps all the ties rusted out.
This is the south coast of Rhode Island, a very high corrosion environment.
Here's the pile of tie-ends that I cut off. Some rusted more than others and that's only a few weeks of exposure. Can't imagine they would have held up well if left on.
DCC - I guess you mean the tie-ends to the interior??
Right. The ones to the exterior are buried and I expect they had completely disintegrated long ago. But it's been 45 years and there are no visible issues.
Reinforcing steel always seems to rust pretty quickly. I'm sure it has something to do with the alloy they use, but I've never really looked into it.
Your wall looks lots better.
BTW, XPS is a better choice for below grade insulation that is in contact with the soil compared to EPS, so you're better off with XPS in this application anyway.
Bill
You did the right thing removing the ties.
You noted this entire wall will be below grade? So you are going to backfill against it on the outside (and have already done so on the inside?
Normally I would say definitely waterproof the wall prior to applying insulation, but in my area, a wall like that would either be a crawl space or basement wall. Not sure in the case of a slab. Definitely apply some type of liquid membrane at the locations where you cut off the ties.