Cleaning and maintaining rain gutters may be one of the most ignored tasks for home owners. We will only drag out the ladder when the gutters are overflowing; water leaking into the basement or there are so many maple seeds growing growing our homes look like a Chia Pet. You do not need me to remind you that cleaning the gutters twice a year is a must. The spring cleaning, after the seeds and helicopters come down, is the most important. Many seeds float and quickly make their way to the depths where it will become clogged in no time. In the fall the weather can change fast and the cold and wet is miserable and dangerous for ladder climbing. I have been in the gutter repair and maintenance business for more than five years and I can tell you late spring cleaning is critical to yearly gutter maintenance.
But you're saying that you clean the gutters twice yearly and the dang things are still hanging off the house with water pooling far away from the downspout giving mosquitoes a perfect breeding pond for their eggs. What is happening is the nails are pulling out of the house and need to be hammered back in. This is a simple and effective way to extend the working life of your gutters indefinitely. The next time you're at the hardware store get a hammer belt hook. This small thick leather devise with a heavy wire loop and slots for your belt is a safe way to carry a claw hammer up and down the ladder. As you move along cleaning the gutter, hammer the nails back in but do not crush the gutter. You should be able to reach three nails but be careful to never reach out to far. A good rule of thumb is to always keep your shoulders within the width of the ladder.
A few solid hits should tighten the nail but what if the nail remains loose? A properly installed nail must penetrate the end of the truss, rafter or ceiling joist. The fascia, nailed to the ends of the trusses, is less than an inch thick and inch inch gutter nails will split the plank then the nail will come loose if done incorrectly. Finding the truss ends is nearly impossible if the fascia has been covered with aluminum or vinyl siding because you can not see the nails used to fix the fascia in place and trying to measure for the truss ends, even if you're 1/16 of an inch off, by the third truss you'll be missing the solid wood necessary to hold the nail.
So you have a gutter that has been ignored for years and you can not tighten the gutter nail. I have cleaned and repaired thousands and thousands of feet of gutters and the hidden hanger with an integral self-drilling screw is the answer. You can get these hangers at the big-box home store but a better bet is to go to a siding and gutter supply house. It is worth the trip as you'll be amazed at the selection and variety of gutter products and tools. This type of hidden hanger uses a inch inch hex-head drive and easily is screwed through the back of the gutter and into the fascia. The screw is at an angle to increase holding power and because it drills its own hole, it is far superior to nails. The smaller diameter self-drilling screw will not split the plank and if you do not hit the truss end will still hold for many years. The problem with the hidden hanger is you'll need clearance to hook it under the upper outside edge of the gutter and then swing it over to clip over the edge of the back of the gutter. If the roof overhang is too great you can not make the swing without prying up the shingles. If the gutter is hanging away from the roof edge put the hangers in place along the offending length, then push up the gutter as best you can, then drive the screws in. Leave the old nails in place to fill the holes.
Another product is gutter screws that replace the gutter nail. These work well if the old nail was in the truss but pulled out anyway. The screws come with a tube to fit inside the gutter and are slightly larger in diameter. The screw is also longer to bite into solid wood. The preferred screw will have a square drive which is supplied in the box. To install a gutter screw you'll have to first pull out the old nail with a pair of locking pliers like Vice-Grips. Then simply drive the screw into the old hole, through the tube and into the wood.
Remember to be careful on ladders and wear over-the-ankle lace-up boots. You'll also need a good battery powered drill / driver, hammer with a belt hook and locking pliers. Keeping those nails tight will extend the life and usefulness of your gutters for years.