Flashing around chimney

toshy321

Anybody know any useful guides for flashing around plastered chimney using tiles any info appreciated

AckwelFoley

Well,parts of it is done prior to plastering, but i assume its a repair job?

I'll be honest, and i dont mean to be rude, but if it something you dont know how to do, you shoudnt do it.

It is one of those things thats not as easy a job to do as you might think, and the folding of the lead on the corners and the fitting of the apron is crucial to do correctly - done incorrectly it will split in time

Putting in the apron and the one at the back is tricky if you're not used to doing it.

toshy321

It's not a repair job, have to flash around chimney on my extension have seen it done a couple of times and would be reasonably confident doing it myself just wouldn't mind some kind of a guide to refresh my memory can't find any useful links through google.

brendankelly

Snyper is right. It is a tricky job that has to be done properly and expensive if done wrongly. The first thing you do is figure out where your plastering bell cast is going to be and then cut a track with an con saw about an inch and a half above where your bell cast is going to be. Then you cut a 6 inch strip of lead about 6 inches longer than the chimney face and bend your lead to fit into the groove. You do this for the 4 sides of the chimney. This lead (the apron) should be secured with lead wedges but everyone uses nails squeezed into the groove with the lead. You then nail on the plaster stop bead. The nails securing the plaster bead will be above the lead and the bottom of the bead should be down about an inch and a half on the apron. Next you plaster the chimney. Make sure the lead on the corners are lapping the right way. Start at the front and fold it into the chimney. Next the sides so the side one is over the front one. then the back. There should be about 3 inches of a lap each way.
Next put on your tiles to the chimney. Then get at least 18 inch lead and cut it 12 inches at least longer than the front of the chimney. You lift up the apron (starting at the back) all around the chimney. You then fold the lead to fit under the apron and stretch it by hitting it with a mallet (never a hammer) until it fits tightly on the tiles and around the corners of the chimney. ( tricky bit of work). Next you cut from your 18 inch roll a bit one inch longer than your tile. you then put on the next row of tiles and leave the lead on top of the tile after folding it. Let as much as you can up under the apron and tap the inch extra over the top/back of the tile. Repeat this process each side for each line of tiles until you come to the back of the chimney. Next you put in extra slating lats at the back of the chimney and cut another strip from your 18 inch roll again at least a foot longer than the chimney. you then fold this under the apron. You have the side aprons already rapped around the chimney. You then bend up about an inch on each end of the lead, Again you tap this into position with your mallet until it fits snugly in place. Then finish your tiling. You then trim the lead so it will look neat.

Please note that it has been 30 years since I flashed a chimney and to be honest I am just testing my memory. Snyper is more experienced I suspect and I hope he will correct me If I have forgotten any thing or if the man I server my time to (RIP) was wrong.

Carlow52

OP:
I recently saw the following being done on a new chimney.

The chimney had been plastered without any provision for the plastering bell cap.

The house owner went and bought a flashing kit for a velux window that matched his roof tiles. It cost 50 euro

Being aluminum it was easy to cut: the top and bottom pieces had to be cut as they were too wide for the chimney but he overlapped them by the width of the chimney and sealed the overlap with a shot of silicone

The side pieces worked fine, they just slid into place.

Fitting the roof tiles was a doddle and then the flashing up-stand was taped to the chimney with a top quality UV resistant weatherproof tape.

Two layers were used so as the underneath layer is protected by the top layer.

The next best alternative he was offered was zinc flashing kit from a well known chimnye supplier for 350 euro plus VAT

Just a thought

AckwelFoley

Just to note, you need to look for 4lb lead - its the grade or thickness, you can get heavier, but its generally only used in the valley of a roof.

Also, patination oil can be brushed onto the lead after its fitted. It prevents the lead running and staining the roof tiles or slates. Smalles amount you can buy is 500ml and will set you back about 10 euro.

The mallet brendan refers to is a lead mallet, not what you would consider an ordinary mallet. If you use a hammer you will leave hammer marks on the lead, but more importantly excessive hammering the lead thins it, and as i said can cause it to crack, and generally at a chimney, where ever the lead is bent is where its crucial not to have a tear in the lead!

toshy321

Thanks lads great help and appreciated I'll attack it myself now as I said before I have seen it done once or twice before but just wanted a bit of a refresher thanks again.