Assembling a clamp-less chimney liner

[runderwo]

I bought an el cheapo stainless steel 6 inch flex chimney liner kit that has interconnecting pieces without the clamps found in higher end setups. Rather, the instructions say to use stainless steel rivets or self-tapping screws and hi-temp silicone to attach the liner to the bottom tee and to the top plate.

Unfortunately some important details are omitted which would probably be obvious to a professional installer but not to me.

1. What size of screws should I use?
2. How many screws should I use at each joint to ensure a solid attachment?
3. Can I use automotive hi-temp RTV silicone or is there some specific chimney liner type silicone I should be using?

 

[DAKSY]

I bought an el cheapo stainless steel 6 inch flex chimney liner kit that has interconnecting pieces without the clamps found in higher end setups. Rather, the instructions say to use stainless steel rivets or self-tapping screws and hi-temp silicone to attach the liner to the bottom tee and to the top plate.

Unfortunately some important details are omitted which would probably be obvious to a professional installer but not to me.

1. What size of screws should I use?
2. How many screws should I use at each joint to ensure a solid attachment?
3. Can I use automotive hi-temp RTV silicone or is there some specific chimney liner type silicone I should be using?

1. Get some SS Zip screws with a 1/4" hex head, 1/2 - 3/4 long...
2. 4 minimum
3. Yes, automotive RTV will work

 

[53flyer]

First, I'm no expert but someone else will surely chime in if I'm way off:

1) 1/4-3/8in would be my thought. You don't want them too long because they'll stick out and make cleaning harder.
2) 3-4 evenly spaced should do assuming it's a decently good connection to begin with.
3) No idea

What make/model liner did you go with?

 

[theheatelement]

Generally speaking their will normally be holes in those locations. I wouldn't say it's a cheapo kit, some people prefer to not spend as much so the manufacturers have to offer something so that they won't go elsewhere. I know that we sell both designs and for a reason.

I bought an el cheapo stainless steel 6 inch flex chimney liner kit that has interconnecting pieces without the clamps found in higher end setups. Rather, the instructions say to use stainless steel rivets or self-tapping screws and hi-temp silicone to attach the liner to the bottom tee and to the top plate.

Unfortunately some important details are omitted which would probably be obvious to a professional installer but not to me.

1. What size of screws should I use?
2. How many screws should I use at each joint to ensure a solid attachment?
3. Can I use automotive hi-temp RTV silicone or is there some specific chimney liner type silicone I should be using?

 

[runderwo]

I said it's el cheapo based on what I paid for it, not that the quality is questionable

I did find it odd that there were no pre drilled holes in either the tee or the top plate.

Is there a specific diameter of screw that would be best?

 

[daryl]

SS rivets with SS washer on back side.

 

[joe245]

#10's would be fine. Like someone mentioned just get them long enough to grab both interconnecting sections

 

[runderwo]

The best I could do at Lowes was #8 1/2" SS. Think that'll be good? The bigger ones came in longer lengths, which if it's necessary to get something bigger, I can just hack off part of the protruding end of the screw inside the duct.

 

[joe245]

I think it would be fine just put a extra one in, Just make sure they are long enough to grab both sections

 

[runderwo]

Tried the #8 screws with a 1/8 pilot hole drilled first. The steel tee ended up stripping the threads clean off the screw. Anything else I can try before I move on to rivets?

 

[joe245]

I would go with a bigger pilot hole, and use a regular steel screw (same size a SS) to cut the threads then remove it and replace it with the SS

 

[runderwo]

When you say use a regular steel screw to cut the threads do you mean a typical zinc plated sheet metal screw from the hardware store assortment bins? Are those stronger than the SS?

Also, 1/8 inch is already about 80% of the diameter of a #8 screw. I'm afraid I won't leave enough metal for the screw to grab onto if I go bigger, is that something to be worried about with these?

 

[joe245]

Run, to be honest I don't know how they compare on the Rockwell scale. I think SS may be softer. You can jump up in 64ths or 32nds with the drill bits and if you did go too big you could see about getting #10 or just going to the rivets like suggested. ARe you using SS zip screws or just regular SS screws. Because the zip screws cut their own pilot hole big enough for the size screw your using which means you don't have to pre drill a pilot hole

 

[runderwo]

I got some self tapping #8 zinc screws, drilled a big enough hole, tapped it out, and now the SS screws go in easy. They don't tighten down all the way, if I keep turning them at the end they'll give some resistance and spin. I think it will be good enough though.

 

[runderwo]

I didn't like the way the screws were just spinning, so instead of drilling holes for more screws, I used the self-drilling screws to start the holes. Most of the SS screws tightened up in the new holes, but a couple ended up spinning anyway. So I just put silicone on the threads and over the head of all the "spinners".

Now, I have a masonry chimney, and there is this squarish 5.5 inch "extension" that looks like clay or something similar that extends out from the top of the masonry, which the existing cap is mounted to. It has about 1" walls. Can I set the top plate on top of this, or do I need to get rid of this and set the top plate on the masonry part of the chimney?

 

[runderwo]

I actually found some #10 SS driller screws, so I started using those and went back over the holes where the #8 screws were turning. Those worked much better and got everything nice and tight. The liner is sitting in there now waiting for the silicone to set up. I decided to just leave that extended clay looking part at the top of the chimney alone and set the top plate on top of it.

Unfortunately my helper at the bottom didn't quite get what I meant by the tee needs to be facing straight forward, so the alignment at the top plate doesn't match the tee. I'll undo the screws at the tee and rotate it, then I should be good to go. I'll post a few pics when I'm done.

I had to remove the frontmost bricks on the smoke shelf using a hammer and pry bar, and also had to cut away some of the damper with an angle grinder, basically rendering it useless. The liner came through not above the damper where smoke from the fireplace would normally have been routed, but below it where there used to be bricks.

One thing that went wrong was the insulation broke/popped apart at about the middle of the liner while I was feeding the liner into the chimney, probably because of the severe angle it was at. I hope that it closed the break back up when the liner straightened back out and it therefore won't be a problem.