Chimney Flu Repair

Usually in the spring and fall I offer to take a look at my clients roof to make sure things are ready and things do not get neglected. 

Some of the things I look for include looking for cement and brick that are weathering and crumbling. 

Last fall I found the 2 chimney flu tiles on this chimney were crumbling and the client and I decided since the snow was coming soon to do a temporary repair until spring. I used some caulking to hold the tile in place. The 2 problem flu tiles are not functional and purely cosmetic but could pose a hazard if they were to come lose in a wind . The other 2 chimney tiles are functional to the right and do not require repair. This instruction is intended to help guide you through steps to repair your Chimney. I suggest reading thru the full instruction before proceeding. 

The plan is to replace the old chimney flu tile and fill the new one with low cost post hole cement to prevent water from building up in the center in winter months and freezing and damaging it again. 

First be sure to use care and safety working around and on your roof. Make sure your ladder is spaced properly from the house and on solid ground to prevent tips and falls. Suggest wearing protective gloves. Good comfortable shoes are important. Choosing the best time of the year and time of day is key to your success to avoid bad weather and too much sunshine.

If the flu tile just has weather cracks they can be filled with caulking similar to that used to fill cracks in your driveway. This flu tile was held in place over winter with caulk but by spring time it was loose and almost ready to move.

One of the problems especially with a cosmetic flu is they can fill up with snow and water and there is no place to go so the freezing in them over the years can take a toll.  

I decided it would be much easier to mix the cement on the ground in small portions and carry up to the chimney. I put down a painters drop cloth near a water source and used  a small bucket. A new chimney flu tile was purchased with the correct outside and height dimension needed. 

Tools need to remover the old tile: 

• Safety Glasses
• Gloves
• Hammer
• Cold Chisel
• Cement Trowel
• Garden shovel
• Broom or leaf blower

Use the hammer and cold chisel to remove the old flu tile flush to the Chimney Cap. It is not necessary to chisel all the old flue tile away since the height of the new flue tile was measured from the Chimney Cap. Use the Trowel, garden shovel and broom/ leaf blower to remove the debris from the chimney cap.

Test the new flu tile on the chimney cap to make sure it does not rock. 

Ready to mix the cement mortar. Suggest using a cement mortar product to secure the new flu tile in place. I chose to use a product from Rapid Set. 

Mix up enough mortar for one flu tile and put it in place as shown. Set the new flu tile in place visually aligning it over the old surface. 

 Use a gloved hand and trowel to press the mortar tight against the inside and outside of the tile. remove excess mortar from the outside and tamp it into the inside edges. remember the inside of the flu tile will be filled with cement later so it is not important that the inside looks good cosmetically. At this point it is important that the outside mortar edge looks clean and flush as shown in the next photo. 

At this point i chose to install the second flu tile and finish it to this same point. My plan was to stop after the second flu tile was in place I allowed then time to set up so if they were bumped, they would not move. 

Next I suggest using a low cost post hole cement to fill the flu tiles to prevent water from being trapped inside where freezing weather can cause damage. I chose to mix the cement in small batches for several reasons. It took 3 mix batches to fill each flu tile. I used two 50 pound bags of post hole cement. The smaller mix batches were easier and safer to carry up the ladder to the chimney.

Use a short piece of wood to tamp down each batch of cement to remove the air and ensure that the cement fits tightly to the inside of the flu tile. Fill the cement and use a trowel to level the cement slightly higher less than 3/16 of an inch than the top of the flu tile. Once again you are trying to prevent water from puddling. Depending on your skills and the cement, a raised dome could also be shaped on the top of the flu tile. 

Here the progress of the work shows one complete flu tile and a second one partially filled.