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Discussion Starter · #1 ·
Hi,

Am I able to effectively (in terms of a water seal) run a new silicone caulk line and join up with an existing one?

For example, in a shower corner where a vertical meets two horizontals, if I need to replace one of those lines can I leave the other two and "join" the new line at that intersection point?

If not, do I have any other choice, but to remove all the caulking from the shower even if just replacing one line? I'd like to avoid the many hours this will take, if I just need to patch one part of it.

Thanks,
Matt
 

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Discussion Starter · #2 ·
In addition to above dilemma (still appreciate some helpful advice if anyone can), I may need to caulk the interior 4 horizontal wall / floor joins of a shower. There are a few challenging bits to take care of so I expect the job will take 30-45 mins.

How would you recommend I take this on? If I go in one direction, by the time I arrive at the finish (joining the finish to the starting point) how will that intersection of caulk turn out? Or should I work in both direction in smaller sections?
 

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For question 2, read the caulk label. There are some silicones that set up and can be expose to water in 30 minutes. Also dependent on heat, humidity, etc. Ron
 

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Discussion Starter · #4 ·
For question 2, read the caulk label. There are some silicones that set up and can be expose to water in 30 minutes. Also dependent on heat, humidity, etc. Ron
Hi Ron,

My question was related to the laying down and joining of the caulk, not so much the time waiting for it to properly set (which the instructions tell me 3 days before exposing to water).

If I start in one corner of the square shower, and work clockwise, when I get to the finish (and have to "join" the caulk to the starting point) around 30-45 mins after starting, how will I join the caulks together?
 

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To answer your first question - No, I don't think silicone on top of silicone is ever going to stick. Even when you peel off the old silicone, its going to leave a film that new silicone will not stick to. I am figuring cleaning it good will not be fun.
 

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You have to (should) remove all of the caulk, don't try to put silicone over silicone. It will take awhile, but the way I do it is to get a razor scraper like this:

http://www.homedepot.com/catalog/productImages/400/53/539c890e-1db2-46d4-acae-40d0a42816ac_400.jpg

Cut out all of the caulk, get some denatured alcohol and some cotton balls. Put the alcohol on the cotton, and apply to the joints, this will loosen up the residue a bit, then scrape the residue, re apply and do again.

Once clean, tape both sides of the joints with painters tape, apply caulk, smooth the caulk, remove tape, and give a final light pass to smooth the caulk joint. Gets a great result each time even if you are not experienced with caulking.
 

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Discussion Starter · #7 ·
To answer your first question - No, I don't think silicone on top of silicone is ever going to stick. Even when you peel off the old silicone, its going to leave a film that new silicone will not stick to. I am figuring cleaning it good will not be fun.
Agreed, am certainly not going to silicone over the top of existing. But I was trying to avoid replacing good caulk, so my curiosity was more on how best to tackle this.

Eg. I have a vertical caulk line running down the wall joins, meeting the shower pan (that has horizontal caulk lines. I was to just redo those horizontal ones and leave the vertical one as-is. So what happens at the intersection when I put new vertical caulk lines in?
 

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McMelb:

Silicone won't stick well to silicone, and so you have to get ALL of the old silicone off. The way to do that is with a product called "Silicone-Be-Gone" which will be sold in the same aisle where they sell caulks. Basically, you cut off as much silicone caulk as you can by mechanical means, and then apply the Silicone-Be-Gone to the remaining thin film of silicone. The Silicone-Be-Gone won't dissolve the silicone, it'll just make it get soft and swell up so that it can be more effectively removed. Use a green Scotchbrite pad to scrub away the softened swollen silicone film. Clean up the Silicone-Be-Gone with water, towel dry and then use a very fine powder (like portland cement) to check that the silicone is gone completely. Apply the fine powder with a paint brush. Wherever there is still any silicone film, regardless of how thin, the powder will stick to and become embedded in that film. If there's no silicone AT ALL remaining on the surface, the powder will wipe off cleanly. Then just apply more Silicone-Be-Gone to those areas where the powder stuck to.

You can also CLEAN mildewed silicone caulk. I'm a landlord and do that all the time.

Mix bleach with BORAX to make a thick slurry. You can buy 20 Mule Team Borax in any supermarket; it will be in the same aisle as laundry detergents. You make up a thick slurry of bleach and borax and spread that slurry over your mildewed silicone caulk with a teaspoon. Then cover the slurry with any type of cling wrap so that it doesn't dry out. Leave it for a few days like that and when you remove the cling wrap and the slurry, your silicone caulk will be as white as Manitoba snow.

In the above instructions the active ingredient is the bleach, so you can use any powder. I find that Borax works best because it makes the slurry kinda sticky so that it sticks well to vertical surfaces. Also, the whole idea behind using the cling wrap is to prevent the bleach from evaporating. ANY moisture barrier will work. I use a wax paper tape which I buy locally because it's faster, but you can use anything that will prevent the bleach from evaporating. Finally, the moisture in the bleach will be bound up in the Borax so that the slurry will solidify. Remove the solidified slurry with a putty knife. Borax is highly soluble in water, so if there's any remaining solidified slurry, just use a wet paint brush to dissolve it.

Hope this helps.
 

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McMelb:

If you end up removing any silicone, then I would cut through the old silicone cleanly a few inches above the shower pan, and then caulk UP TO the old silicone with new silicone. The two silicones won't stick to one another, but the fact that they butt up to each other will prevent any significant water leaks. You want to make sure that any joint between new silicone and old silicone is in a place where that joint is NOT submerged in water because then you will get water leakage at that joint. Having the joint a few inches above the shower pan will hopefully prevent any water leakage because the joint won't be submerged.
 
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