The Engineering of How Gutters Work?

The Engineering of How Gutters Work


We seem them every day and probably never stop to think about gutters. Why do we need to fit gutters to our houses? why not just let the rain fall straight off the roof onto the ground below?

The engineering of how gutters work is a complex topic and great amounts of thought are given to angles of the roof and dimensions of the gutter to provide optimum drainage. Houses generally need gutters for a variety of reasons which we will explore in this article`. They have been around since the Roman times and will be around for the foreseeable future.

History of Gutters


The Romans brought systems for managing rainwater when they invaded Britain. After the fall of the Roman Empire that technology was once again lost by the population of Britain, until it was reintroduced by the Normans.

In 1240 King Henry wanted the insides and outsides of the Tower of London “whitened”as was the custom of the day. He subsequently asked for the towers lead guttering to be extended, so that rainwater would not spoil the walls.


In the time of the Saxons buildings were erected with large roofs that overhung the walls, so that water would fall onto the ground, well clear of the houses. Pretty much the same method as was used in thatched cottages. The Saxons were a germanic people that settled in the South-East of England and spread outwards across the rest of England. On large buildings like cathedrals the architects used lead parapet gutter that fed into large Gargoyles. When the monasteries were dissolved, this had a side effect of leaving lots of lead to be recycled into secular building use. Poorer people used wooden gutters or wooden gutters lined with lead.

The Industrial Revolution

When they built the innovative Crystal Palace, the wooden beams that spanned the space between roof girders had a deep channel cut into the top to serve as a gutter. These were called Paxton Gutters, named after the architect, Joseph Paxton.

With the industrial revolution there came better ways of casting iron and the railways allowed these heavy cast iron gutters to be transported to building sites. The new cities built at the time had to be made compact and this increased the need for gutters that channeled the rainwater In 1849 proposed a sewerage system for London with houses having gutter connected to downpipes which fed the rainwater into the sewers. By the 1870s all buildings were built with gutters and downpipes.

Various materials were used for the construction of these rainwater disposal systems.

Types of Materials used in Construction

Cast iron

Cast iron systems first appeared in the latter part of the 18th century as an alternative to the previous lead systems.Using cast iron made mass production possible They were a better solution than the previous wood gutters with lead linings. They were much easier to install and became the standard solution. Where historic buildings are being restored they still sometimes use Cast iron, but often these days they will substitute aluminium that is made to the same design.


Today, in the Uk most guttering now made using PVC. This material was first introduced in specialist systems in the 1930s and use grew rapidly till by the 1950s it was becoming common. By 1970 some 60% of all rainwater systems were constructed of PVC.

PVC is simple to instal, lightweight, and has a predicted lifespan of 60 years. The primary disadvantage is its expansion. PVC will expand 7.2mm within its end stops if temperatures of −5 C to 25 C occur. A general rule is that a 4″gutter with a 2.7″downpipe will drain a 600 sq ft roof.

Stainless Steel

Higher quality stainless steel systems have been introduced with superior looks, greater durability, amd resistance to corrosion.

Seamless Gutters

Seamless gutters are manufactured on site by specialist staff. They can be made to suit individual building configurations with a roll forming machine. It typically has a lifespan of 30 years,


Another alternative in the UK is zinc covered mild steel. This is corrosive resistant.

Concrete Gutters

Concrete Gutters (aka Finlock gutters) were common in the 1950s and 1960s. They can be fitted to a variety of building types. They mainly were used at times when other materials were in short supply. They are not an ideal solution and problems abound.

How Much Water Can You Collect From Your Roof?

The roof of a modest house can collect large amounts of water when it rains. This water has to go somewhere and it can either be allowed to cause damage or can be used constructively. This is one of the purposes of guttering.

There are many uses that you can put the water you collect to. It can be used for watering the garden and for cleaning. With the right kind of filtering equipment it can even be used fro a drinking water supply. You roof is the perfect water collector surface.

The formula that you can use for calculating how much water you can gather from your roof is

Gallons collected per inch of rainfall ≈ 0.62 • total collecting area of roof in square feet

So for a house with 1,000 sq ft of space, you retrieve 0.62 x 1,000 = 620 gallons of water each time that you get one inch of rain. With two inches of rain you can collect 1,240 gallons of FREE water.

Rainwater and the Foundations of Your House

Now we will look at the other side of the equation. We have seen how much valuable water you can collect free when it rains, but what happens if you are not collecting it and you have no guttering system?

If you have inadequate ways of driving water away from your property then your garden can sometimes turn into a swamp every time it rains. All the water we mentioned in the last section not only doesn’t get used but instead it is just dumped onto your garden. This water can do a lot of damage to the foundations of your home. Maybe you will not see a problem for a year or two, maybe not five years, but at some stage damage will appear, and this can be very expensive to fix.

If your have a system of gutters and downpipes channeling this water then this problem can be avoided and your garden will no longer be a muddy swamp. You need to think out where this water is going to go.

Options for diverting rainwater from your roof

Sewerage System

The most obvious solution is to connect up your downpipes to the same system that takes away your waste water from inside the house. The water is then taken well away from your house and eventually will make its way through the sewerage system into the ocean.

Rain Barrels

If you want to take advantage of this free water supply that rainwater provides, then you need a system of channeling the downpipes into your water storage barrels. A Barrel to store the water will cost around $50 and you will need to create some sort of filter to stop debris flowing into the barrel. A simple system will just have one barrel with a tap at the bottom, so you can get the water out of the barrel. You also need to buy or make the filtering system.

What happens if you have more rain that your requirements for water to irrigate the garden? If you find the barrel is overflowing then you have options. You can either connect up a second (a subsequent) barrels so the first will overflow into the second and so on. You may instead choose to link the overflow pipe to an underground pipe that takes the excess water outside of your property to the gutter in the road outside.

Should you want to use the water for drinking the system becomes much more complex in order to maintain the purity and purify the water.

Dry Well

Another solution is to link up the downspouts to a pipe that feeds the excess water from the roof into a dry well. This is a dry bottomless barrel that is surrounded by gravel and other porous material so that water that flows into the well filters away through the gravel back into the soil. This should be placed well away from the house ideally down hill.

Rainwater Harvesting Systems

Rainwater Barrels, Rainwater tanks, Water Butts, are containers for storing water that has been harvested from roofs via gutters and downpipes.. This is sometimes called a rainwater harvesting system. As we have seen earlier, just one inch of rain can produce 640 gallons of water to be harvested for a 1000 sq ft roof area.

Having such a system allows the water collected to be used for activities that do not require drinking water quality. This is done for environmental reasons or sometimes to reduce costs of water purchased from your water supplier.

In some parts of the world water is collected during the rainy season for subsequent use in the more arid seasons of the year.

This may be a solution for providing drinking water, with proper filtration and maintenance, but I will not go in to this in this article. It is a more specialist topic. We will concentrate on storing water that is not for human consumption.

Water Tanks

Water tanks connected up to gutters and downpipes can be a very efficient way of managing water on your property. First off the tanks should be constructed from an opaque material so that “algae blooms”are not encouraged. Materials could include Polyethylene, Concrete, Galvanized Steel, as well as fiberglass and stainless steel. These materials are both rust and chemical resistant. virtually all steel rainwater tanks are equipped with a plastic lining to prolong the working life of the tank.

Typically tanks are covered and include screened inlets which stop insects, debris, animals, and and bird droppings.

Reasons to install Gutters

If your home does not already have gutters, you may think about cutting corners and not installing them. This is a big mistake as various things will happen:

Siding damage

No gutters means that water will drain straight off your roof and down the side of the house. Ultimately it will start to pool around the foundations of the hose and cause potential damage., This will mean that the debris filled water from your roof will pour down and leave debris on places it touches enroute. If your house has sidings they will get stained, dirty, and if wooden, be subject to rot.


Once again I refer to the vast amount of water that your roof can attract. Hundreds of gallons of water pouring straight off your roof like a waterfall. This will generate a lot of pressure on the foundations and will carve its way through flower beds and other garden features. If your house has a basement then it may well get flooded or at the very least attract mould.


Houses built on slopes will see the waterfall of water flooding onto the soil start to carry it away every time it rains. Gradually eroding the soil and dropping the ground level, with consequent impact on the foundations.

Final Thoughts on Guttering

We have seen that gutters Salem Oregon, the attached downpipes and the facilities for carrying off the water are all part of an integrated system that is put in place to protect your home, securing the integrity of the foundations and stopping your garden turning into a muddy swamp every time it rains.

Water is a powerful force as we can see from the Grand Canyon, which was carved from water over 6 million years, The daily flow of water from a house without gutters can do significant damage if no action is taken. By not having gutter, you are also losing the oportunity to harvest rainwater, a resource that is going to be particularly valuable in the future.