Block Off Plate Insulation

[DenD]

After reading all of the posts about block off plates, I've decided to fabricate one this week. Elk's posts have scared me enough to stop burning until the plate is in place. Somehow the dealer/installer convinced me it wasn't necessary to install one, but now I know better.

The plate itself is plate itself will be pretty straight forward - 2-piece 22 gauge steel installed with masonry screws and furnace cement. My question is related to insulation - Craig's instructions don't mention insulation, but I have seen other folks mentioning using Kaowool. What is the consensus regrading insulation? My insert is in an exterior masonry chimney, should I insulate? (I would think so) If so, what is the proper way to insulate? Should the Kaowool be placed on top of the plate or should it be used to wrap the liner and fill the opening through the removed damper area?

I've found Kaowool blankets on (broken link removed) I've also found mineral wool insulation on www.mcmaster.com. Does anyone have advice on the best product to use?

 

[webbie]

I say no need for insulation as long as you seal it well around the edges, etc.

Exception would be if a hot radiant surface of the stove is within a few inches of it....usually not the cast.

 

[Rhone]

If I were you, I'd get the kaowool and use it to insulate the inside of your fireplace before putting in the insert or try to sneak it behind it. Use tapcons to hold it in place, that will make a difference especially with outside chimneys. You'll probably have some left over, I'd put it above the block-off plate just to complete it though I agree with Craig I don't feel it will make much difference there if it's sealed tight on top and bottom. I happen to put 6" of slag wool insulation above my block-off... overkill but I feel better I overkilled than wondering how much difference would it make, and had I only put it there while I had the chance.

 

[DenD]

Thanks for the responses so far.

Now that the bottom of the chimney will be taken care of, my thoughts are turning to the top. Since my installer didn't properly seal the damper area, I have doubts that the top of the chimney was sealed correctly. What is the proper method for sealing the liner at the top? What should I be looking for?

 

[Rhone]

On the top, you should see everything caulked with silicone. Here's a picture of mine, you can see the top plate caulked to the cement chimney cap. The storm collar caulked to the top plate, and the joint where the liner passes through caulked as well. Even the clamp & seams of the storm collar were caulked. You get the hint nothing should be left uncaulked and it should be RTV silicone, hard to tell between regular.

If you find problems, you're in for some work. Silicone can stick to almost anything, but it WILL NOT stick to itself. If you go up there, and some of the seals are blown you need to scrape off all the Silicone and reapply. In this picture, you can see my storm collar seals have blown and aren't sealed anymore to the top plate (you can notice it particularly below the storm collar sticker). I scraped it all off and reapplied. The best way to apply it, is to apply the silicone underneath and push it down so it glues the system together than it is to put everything together and afterward silicone around the joints.

 

[Hogwildz]

On the top, you should see everything caulked with silicone. Here's a picture of mine, you can see the top plate caulked to the cement chimney cap. The storm collar caulked to the top plate, and the joint where the liner passes through caulked as well. Even the clamp & seams of the storm collar were caulked. You get the hint nothing should be left uncaulked and it should be RTV silicone, hard to tell between regular.

If you find problems, you're in for some work. Silicone can stick to almost anything, but it WILL NOT stick to itself. If you go up there, and some of the seals are blown you need to scrape off all the Silicone and reapply. In this picture, you can see my storm collar seals have blown and aren't sealed anymore to the top plate (you can notice it particularly below the storm collar sticker). I scraped it all off and reapplied. The best way to apply it, is to apply the silicone underneath and push it down so it glues the system together than it is to put everything together and afterward silicone around the joints.

Ah silicone, now thats a subject I know quite a bit about from my roofing & siding days. Silicone is really not the best sealant for alot of applications. Or at least normal silicone caulk isn't. Silicone can be applied to itself. The trick is and even in a fresh install of it, you must work it into the surface you are sealing. Just gliding it on or globbing it over does not last long. No matter what the surface, we used to use our finger and work it in, usually in a circular manor. Looks almost like a welding weld when done. If its a striaght line like a corner or such, run yer finger and smear it in one direction along the seam, then reverse and run your finger the 180 degree opposite direction. I found that only good for tight corners or 90 degree seams. I have put silicone over old silicone and it stuck just fine. But I worked it in real good.

Of all the caulks I have used, and I have used many dif kinds. Urethane caulk is by far more superior to any other I have ever used. It never hardens, can be painted, and is reall great at bonding to many surfaces. A couple examples: Masons use it in expansion joints in walls & floors. 1 week after I bought this place, this and 3 or 4 other counties received about 13" of rain in a day & 1/2. Flooding everywhere. I am on the mountain, but when I came the weekend after settlement, I found the basement full of 5' of water. it drained out the semi clogged drain. Didnt know where it got in. Next heavy rain, I go down and hear a waterfall sound. Its a pipe going through the side wall connected to nothing and " silicone sealed around it. Well the silicone didn't hold and the water was pouring in around it. I am talkng about an 1" hole with a hose like stream of water pouring out of it. I grabbed my caulk gun already with an open tube of urethane, pulled the pipe going to nowhere out, and pumped about 5 or 6 pumps worth in the hole. Even with water pouring in, it stopped the leak dead. Never touched it again and never had water there again.
Works great around chimney storm collars also.

Be warned though, this stuff is great, but takes several days to a couple weeks to skim & cure. Depends on the weather, humidity level etc. It never hardens so to say. Its like rubber when cured, firm but not rock hard. I used it to seal the gap between an uneven door plate and the fresh concrete poured earlier last summer, worked like a charm. Like a big ol expansion joint and even had a concrete color. I have bronze for around the windows/siding etc for this house. I love this stuff. It lasts forever also. Try it next time you scrape that silicone off. But clean the siliconed area with solvent once the silicone is removed. Another prob with silicone is it leaves an oil behind on the surface, that nothing other than silicone will stick to again.

Stay away from latex caulk for anything, with the exception of sealing indoor wall cracks at the corners of wall, works good for that, anything else, forget it, it cracks, peels & falls off with the next change in climate.

BTW, that storm collar, shouldn't be sitting on the plate, it should be raised up a few inches. Not trying to be a knowit all, but this stuff I truly have dealt with for many years.

Try the urethane next time, u can get it at HD. Its really excelent sealant. It costs more but lasts 10x as long as silicone.

 

[elkimmeg]

Fellow roofer great advice

 

[Hogwildz]

Fellow roofer great advice

Thanks Elk, feels good to be able to share some knowledge for once, rather then pester all you guys for info. Giving back in my own way.

 

[Rhone]

Boy Hogwildz, that was a very useful post. I'm replacing and caulking windows and I'm glad you went the step to say how it should be done, I've been having a very hard time with the corners of the windows, now I know with the finger one pass down, one pass up. I followed the directions on my liner setup (Heat Fab) which wants the storm collar resting on the top plate, possibly others don't. I did see the instructions say use silicone for the top plate to the cement cap (my guess silicone can handle higher temps than urethane (500F vs. 250F)), but I just realized it doesn't say to caulk the storm collar. Maybe I wasn't supposed to go that far with the caulking.

I love urethane as well. I've been using it to adhere the XPS foam insulation around the exterior of my foundation and then fastening it with tapcons & fender washers. I like how it takes a long time to adhere, you can move the object after you've applied it within 30 minutes with no affect on adhesive strength. Around pipe penetrations and the like, I use urethane foam. I too am not a fan of latex, it shrinks, doesn't adhere as well, I find mold/mildew loves it when used in high moisture areas. Looking into something else now.

 

[Hogwildz]

Boy Hogwildz, that was a very useful post. I'm replacing and caulking windows and I'm glad you went the step to say how it should be done, I've been having a very hard time with the corners of the windows, now I know with the finger one pass down, one pass up. I followed the directions on my liner setup (Heat Fab) which wants the storm collar resting on the top plate, possibly others don't. I did see the instructions say use silicone for the top plate to the cement cap (my guess silicone can handle higher temps than urethane (500F vs. 250F)), but I just realized it doesn't say to caulk the storm collar. Maybe I wasn't supposed to go that far with the caulking.

I love urethane as well. I've been using it to adhere the XPS foam insulation around the exterior of my foundation and then fastening it with tapcons & fender washers. I like how it takes a long time to adhere, you can move the object after you've applied it within 30 minutes with no affect on adhesive strength. Around pipe penetrations and the like, I use urethane foam. I too am not a fan of latex, it shrinks, doesn't adhere as well, I find mold/mildew loves it when used in high moisture areas. Looking into something else now.

The top of the collar around the pipe should be caulked. Thats basically all that keeps rain water from running down the pipe behind the collar. I know it seems like such a small crack, but rain will run down there. I had to point that out to my old neighbor when he complained about his roof leaking. For the most part, shingle roofs don't leak at the shingles often. Its the flashing & penetrations that leak. Alot of homeowners just don't realize this. I would caulk the top of the storm collar, but not the bottom. This way if water does get down around the pipe for any reason, your not sealing a pocked for the water to build up in. if the bottom isn't caulked, the water will just run out and across plate and off top as it should. I would also seal where the pipe comes through the plate if you didn't already. But lose the caulk on the bottom lip of the collar, thats just asking for trouble. Water dam.

When you caulk those window corners, trick of the trade is put a generous amount of spit on your finger your spreading with, its does a few things:
Smooths the caulk real nice, helps keep the caulk from sticking to your finger, therefore the caulk both glides and spreads much easier. I know it sounds gross, tastes even worse, but works great. Comes in handy especially with that sticky urethane caulk. When the caulk starts to stick again, just wipe finger good with rag, add more generous amounts of spit, and glide right on along. LOL Really does work, I do it no other way. I tried water and other liquids, they just didn't work as well.

I also like that urethane is workable for much, much longer than the other caulks. Makes repairing boo boo's easier. When I did the threshold to the front door of old house, the kids kept stepping on it, man I was fit to be tied. repair, repair repair, then laid a small board over it and told them to step over the board LOL.

One more trick I use when caulking and looks are important, is to use masking tape on each side, or the visible side of the caulk bead. This is set at the edge where I want the caulk to end. Say I want a 1/4" bead, I set the tape edge 1/4" from the corner or area I am caulking, then pump the caulk, saliva up finger, spread said caulk, then pull tape off before caulk dries. Wallah, nice clean caulk line. Its tougher to do it with the urethane, it tends to want to stick to tape & area caulked bridging both when you pull the tape off. then that stringer letting go and springing or flopping onto you clean surface, ARGHHH. If you don't go crazy heavy with the caulk, and after you spread, only have a thin layer over the pate edge, it comes off clean and a nice straight line. For windows, you prolly won't need that though. Just don't go mega heavy with the caulk. what you think is a little, when you spread with your finger, can turn out to be alot. I always use just enough that my finger spreads it across both surfaces, in a nice thin bead, not 1/2" of caulk on each side, and isn't "plowing" it into a major blob as I glide my finger along the corner. Thats where it gets sloppy, messy, and the bead looks like hell.

Windows can be a pain in the arse. Good luck.