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I’m thinking of making a small shop and thought I could use a free standing woodstove for heat. It’s going to be a simple cmu crawl space and I was going to make the chimney out of them too. My question is, when you put in the flue liner, is it best to fill the space between the cmu and liner solid with mortar or is it better to try and leave air spaces and concentrate on sealing the liner joints? Thanks
William
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William, You should never fill solid with mortar around a flue liner. The liner will expand when heated and crack because it is restricted by the block and then the block will crack and leave an opening right to the outside of the chimney. Either leave an air space or fill with Perlite between the liner and the block or brick. I like to use Perlite because it holds the flues in place as you lay them and insulates them after construction is completed.
*Better yet is to use stainless steel insulated chimney. Run your black pipe to the stainless insulated pipe. Be sure to put a safety where the pipe penetrates any flammable material.Then, most important of all: Clean The Chimney Every Year Or More Frequently If You Burn A Lot Of Soft Wood.
*Fred, Stainless steel insulated instead of flue liner? That's a bit more than I wanted to spend for this small outdoor shop. All I burn is hickory and oak, seasoned, and I still have to clean out my chimney once a year and sometimes twice. It's probably because I keep the air vent almost closed most of the time.You are right to keep it clean. William
*Well it certainly is your choice. But, I have seen lots of chimney fires with cmu and relatively few with the safety pipe. Plus, the damage when there is a fire in the safety pipe is generally restricted to the pipe itself, it must be replaced if subjected to overtemp, above 1200 or 1400 degrees if memory serves.It really isn't that much difference in cost when you consider it is normally a once or twice in a lifetime expense and it is certainly safer.By the way, in case there is a question I'm not talking about a flue liner. I'm talking about black pipe from the stove to stainless safety pipe through the wall and up the outside. I'm not a fan of flue liners for wood stoves unless it is needed for architectural reasons. You certainly don't have that requirement.
*Then what would you recommend for a liner in a masonry chimney? I've always heard that they are never to be unlinedMike
*I take it you have a wood stove and masonry chimney already installed? Or, are you just going to install a new wood stove and chimney and must use masonry?While lots of folks use the stainless safety pipe for oil/gas fired heat plants I see no problem at all with masonry chimneys if that is what you want to do. Use either one of a variety of metal or fired ceramic liners. Or, you could do what was suggested by Mr LaLonde. They don't have the fire hazard that wood stoves have. With them you are more concerned with the hazards of corrosive exhaust.
*I was more looking for some clarification, as I didn't understand what you were saying. Yes, I'm installing a wood fired furnace into an existing unlined brick chimney. I'm planning to line it with the flexible stainless stuff. I've still hired a pro to come look at it and suggest an appropriate course of action.Mike, the idiot DIY guy
*Fred, I Thought you meant to use ins. stainless steel inside cmu instead of clay flue liner. Sorry. Your way would be cheaper and faster but is a metal pipe really safer than a block chimney? And how about when the next hurricaine comes by for a visit? William
*Safer? You bet! One of the biggest hazards to a wood stove installation is creosote accumulation in the chimney. A round stainless safety pipe can be cleaned with the correct size brush in a few minutes. Also, the insulated safety pipe can keep chimney fire overtemps confined within the pipe. Makes the fire sound like a jet engine at full Take Off power and looks like blow torch; but it is all outside. Can't say the same for cmu unless you spend a lot of time and money doing a custom insulation job.As for wind resistance: I have seen these routinely take winds in excess of 100mph in mountain passes and river valleys. So, I think they should do as good a job of handling a hurricane as the rest of the structure.By the way, whatever you choose be sure it is correctly sized for the particular stove you are using. Use the correct size to get the best draft and least creosote.By the way; Mike you are far from an idiot. Anyone who knows their own limits and gets help when beyond them is showing one of the key parts of wisdom.
*FredB, Is there a place in the bottom for all the creasote to collect after you clean out the pipe? The one I've used (cmu) has a little door at the bottom that I use to clean out what falls down when I run my rectangular wire brush down it a couple of times. Pretty simple. Does the metal pipe have a section on the bottom kind of like that or do you have to take out the L joint at the bottom? William
*Well since from your post I take it you haven't built this shop yet why not just take the stack right out the top of the stove and up through the roof? Then the cleanings fall down inside the stove to be removed just like the ash. If you put a horizontal from the stove through the wall that becomes a creosote trap. While you can put a removable bottom on the vertical the horizontal is a cleaning pain, interferes with the draft and in general is a poor idea.From this last question I take it you have never used a wood stove. Maybe I could find you a book or something to help you safely use one?
*FredB Actually I had a free standing stove for 15 years with a brick chimney. That's what got me interested in that form of heat. We just moved into the house I built and I wanted another wood stove but the boss said NO! Apparantly something about the sut and smoke smell,I'm not sure what she's talking about. Anyway, I put in a Heatmor outside woodstove to heat the house and our hot water. Been using for just over a year now and it is great. I got tired of getting wet everytime it rained and I had to fill the woodstove so I built sort of a carport from the house to the stove and it is also a great place to keep the firewood. That is when I encountered Stainless steel insulated pipe for the first time. I had to get the chimney from the stove up thru the ceiling and then out the roof. Soon I will be starting on my workshop and that is where I'll be putting a free standing woodstove( The Boss doesn't go in there).I like your idea about having the pipe all inside.William
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I'm thinking of making a small shop and thought I could use a free standing woodstove for heat. It's going to be a simple cmu crawl space and I was going to make the chimney out of them too. My question is, when you put in the flue liner, is it best to fill the space between the cmu and liner solid with mortar or is it better to try and leave air spaces and concentrate on sealing the liner joints? Thanks
William