If your slate roof has a rusted and leaking box or center or parapet wall gutter, what do you do.
Because of the volume of rainwater these gutters have to cope with, when they leak you can always be sure that it’s going to be a big one – if not the first time, it will happen sooner rather than later. So when you do suspect that your gutter is beginning to leak, it’s wise not to ignore it and get it sorted pretty quickly.
Many of Melbourne’s Victorian and Edwardian era period homes are well over 100 years old now. Surprisingly there are still many of these homes still with their original untouched slate roofs and original guttering. The last two or three years we have seen an increase in the number of these gutters that we have been replacing. Most recently a tapering parapet wall gutter on a Victorian terrace home in North Melbourne built in 1874. Not a bad innings for an original gutter if you ask us. The long life of this gutter may be explained by fact that someone over the years had kept it painted up and prevented the rust from getting a foothold on it. In the end though the rust had got started and eventually wore a hole right through and caused much damage. When these gutters do rust through you can sometimes cut out the affected area and repair it with a small section of gutter married in to the original. In our experience though there will be other sections that will also rust through and leak in the near future. So you need to look at the condition of the whole gutter and decide whether it’s worth trying to repair… or better to replace the entire length.
So how do you replace your rusted, leaking box or center or parapet wall gutters
In all honesty it’s something…what do they say… ” simple but not easy “. That probably sums it up pretty good.
Lets assume that you want to replace a tapering center gutter…sometimes [ incorrectly ] just called a box gutter… that’s five meters long, running down the middle of your Victorian period home. There can be other areas where these gutters are installed but most commonly they’re directly above your central hallway.
If you’ve decided to replace the entire gutter here’s the steps that we follow that may help you.
- Get the measurements of the original gutter – At the widest end of the gutter, where it begins to run up the slope of the roof, measure the width across the base. Lets assume that it’s 300 mm. At the other end where it begins to fold down, measure across the gutter. Lets say this is 150mm. At the end that’s 300 allow another 300 mm to go up the roof under the slate tiles. At the end that’s 150 add what ever length is required for the gutter to reach the spout or sometimes rainhead. Lets say that it’s 100 mm from the end to the spout. Allow 250 mm or whatever is required at the sides to get up under the slates by at least 75 mm. So in total you need a gutter made up that’s 5.4 m long. Take those measurements along to a plumbing supplies shop, tell them what it’s for and also the approximate pitch of the roof. They should get the gutter folded a little shallower than the pitch so as to allow it to sit tightly on the gutter boards. When you get the replacement gutter at home, re-check the measurements to make sure it will fit
- Remove the bottom 2-3 rows of slate that are closest to the gutter – Make sure you choose a day when there is no rain forecast. Starting at the highest row of slates that you’ve determined need to come out to remove the gutter ; use a slate puller or a long metal saw blade to cut the nails holding the slates in their positions. Work your way right around the roof removing this course. This first row of slates you’re removing will be the hardest to remove. The courses below it will be easily removed with a claw hammer as the nail heads are now exposed. Where the two valley irons come down onto the gutter, gently fold them up just enough to be out of the way. At the other end, remove the nails or screws holding the hip capping and simply remove them until the new gutter is in. When all these slates are off, the entire gutter is exposed.
- Remove the old gutter – Now its simply a matter of lifting out the old gutter… you may find a few nails holding it down but more often than not it will be just sitting there.
- Install the new center gutter – Before taking the new gutter up on the roof do the following. At the widest end, cut in along the fold line for 300 mm. This is the amount you previously determined to go up the roof under the valley irons and slates. At the other end, again cut along the fold lines for 100 mm. This is for the gutter to be folded down into the spout. Carry the gutter up and put it in position. The end you cut to fold up the roof under the valleys will fold over each other. Lift the metal on each side and put plenty of silicone under each flap. Now, making sure the gutter is firmly in position, rivet the joins together with stainless steel rivets spaced 20 mm apart. Make sure the silicone is covering the whole join adequately to ensure a water tight joint. At the other end, when the metal is folded down and into the gutter fold down the sides onto the slates at the end of the roof.There will be gaps where the end is folded down that need to be fitted with gussets, siliconed and riveted also.
- Re-install the roof slates – Fold down the valley irons back to their original position. Starting at the lowest course, relay the slates back to where they were. They don’t have to go back to the exact same spot although the valley and hip cuts will. When you get to the last course [ the one that you removed first ] you’ll maybe need to wiggle and jiggle them a bit so as to get them right up into their correct spot under the slates that haven’t been removed. Before putting the last course of slates back on, you’ll need some way of holding them in position as the nail holes won’t be exposed. There are two ways commonly done here…. You can nail a narrow metal strip to the exposed batten so as when the slate is slid into position it’s long enough to be folded back up the roof over the slate and thus holding it in position. The other way that is sometimes done is to simply put a big dob of silicone on the slate below and then slide the slate into its position. When the silicone sets, the slate should not be able to be slid out again. We actually use another method to put these slates back in, but for the D.I.Y. person this is sufficient. Re fix the hip capping and you’re all done.
Replacing box gutters, valley gutters and tapering gutters on slate roofs is something that can be done by a competent homeowner…. it can be simple but not easy. There are a few other things that often need to be considered. If the slates on your roof are just an average quality you may need to have a ready supply of the same size slate to allow for breakages. Also, it’s a good idea to make sure the job gets done in one day. It would not be a good idea to leave it exposed overnight… the weather in Melbourne can change quickly and it can be difficult to tarp these areas properly.