Poor Man's Kerdi Fix

[MNTileGuy]

I was in a pinch the other day on a job and went to the nearest Homer and got a tube of Sika construction adhesive. Is this the stuff some of you have been using? At roughly $6 a tube, the price was right. It certainly seemed very similar to k-fix and definitely sticks to skin every bit as well.

[John Bridge]

Sika is good stuff. They make a range of products that come in a tube, though, so take note of the product you've bought.

[Houston Remodeler]

this stuff

[MNTileGuy]

That's the stuff, Paul! I was surprised that white was a little cheaper than the gray too. Needless to say, I went with the white.

I guess I know what I'll be using from here on out.

[Houston Remodeler]

Not only is it cheaper, but its more readily available and usually much fresher than the inventory at the local tile warehouse where its not air conditioned like it is inside home burrito

[jadnashua]

FWIW, Sika Construction Adhesive is a urethane based material, KerdiFix is a silane based material. Sika DOES make a silane based adhesive, but it is about the same price as KerdiFix - Sikaflex®-505 UV is their closest product to KerdiFix, at least when comparing specs.

[Lazarus]

Well, I know it rocks! Paul turned me onto it, lo..those many years ago....

[MNTileGuy]

So what are the pros and cons of silane vs urethane?

[jadnashua]

The Sika Construction adhesive is tack free in 1-2 hours, the KerdiFix, about 10-minutes. KerdiFix cures about 1/8"/24-hours, Sika Construction adhesive takes 2-5 days, depending on conditions (the KerdiFix, since it doesn't have VOC's, is pretty consistent, regardless of the conditions and in fact, will cure underwater just fine - Sika Construction adhesive will fail under water if it hasn't cured first - they call for a minimum of 5-days). The Sika, once opened, is shot in about a day regardless how well you seal it - ever played with Gorilla Glue - moisture starts the cure, even a little bit. KerdiFix has a longer unopened shelf life and is still good for maybe a week on a partially used tube (maybe a bit longer). Sika Construction adhesives has a significant VOC content, KerdiFix has zero (and is 100% solids, so it doesn't shrink). Moisture from the substrate can cause Sika Construction adhesive to bubble up...once cured, KerdiFix is a solid since it has no VOC's, and thus, no voids from where the VOC's evaporated from. Service temperature range on the Sika is max 170F, KerdiFix is 212, and 365 for less than 30-minutes, so could be a factor in a steam shower. Bond strength on KerdiFix is about twice that of Sika Construction adhesive, but the exact amount depends on the actual materials being bonded (either is higher than the shear strength of Kerdi).

IMHO, they are not interchangeable. You get what you pay for. For most things, it may work. No idea long-term bond, but I'd bet KerdiFix (or a similar material) would outlast a urethane based adhesive.

[HS345]

I'll not be using the cheaper stuff anytime soon.

[jadnashua]

Note, as I said in an earlier post, Sika DOES make a silane based adhesive, but it costs about the same as KerdiFix, and doesn't seem to be stocked all that many places, probably because of the cost and the turnover to maintain it within the shelf-life. It tends to get used at RV dealers for a sealant, and you might check there if you can't find KerdiFix and are in a bind.

[MNTileGuy]

Well, there you go trying to burst my bubble, Jim.

Any rebuttal to Jim's remarks, Paul? I'm not trying to bait you into a pi$$ing match, but I do put a lot of weight into your opinion. It also sounds like you've been using this in place of k-fix for some time, so you have a god bit of real world experience with it.

All I can say is I still have hints of it stuck in my fingernails 5 days later. That's pretty tenacious in my book.

[cx]

I would personally not hesitate to use the SikaFlex Construction Sealant as a KerdiFix substitute for any application you conjure up, Brad.

When testing the below pictured pookies (I really need to get that published on the main site) with various sheet waterproofing membranes it was among my favorites.



My opinion; worth price charged.

[Lazarus]

"Tack Free" in 2 hours vs 20 minutes...? So what? Gotta let it set for a couple of days before using it underwater? Uh...yeah.

I've used it over washers on Kerdi-Board, used it for setting fixtures. A little extra drying time is, to me, a non-issue. The fact that it's 1/4 the price of Kerdi Fix is....

[Davy]

I'm not a Kerdi guy so how many tubes do you use in a shower? I'm sure the Sika adhesives are good but if I'm going to install a Kerdi shower, I'll make sure I have a couple tubes of K-fix on hand. I can see if you're in a pinch using the best product you can find but I'm not going to use the Sika just to save a few bucks. If I can't afford the K-fix, I'll go up on my prices so I can use the recommended adhesive. But, that's just me.