Concrete Interlock Tile
Redland first introduced concrete interlocking roof tiles in 1919, Marley in 1924. They became more common in the 60's and are the only choice now for many developers.
This is down to costs, Interlocking tiles cover a large area and the labour is less intensive. This gives the builder little incentive to use anything else.
Slate has been used on roofs for hundreds of years. They look good on any roof, and will outlast ANY manufactured product. We have done many re-slates which have been on 3-4 times prior to us re-slating. Most as good now as when they where first laid, often 100 years ago at least.
Up until recent years, all slates on our roofs would have been sourced from UK quarries, many from Wales and Cumbria. These slates will more often than not last hundreds of years.
Almost all re slates which we do are not down to problems with the slates themselves, but more often than not the nails themselves have perished. Also, felt was only introduced around the 1950’s so prior to this the slates where back pointed. This was to prevent ingress of water from driving rain.
Often this has fallen out and when looking in the loft can make many people worry as rain can and does find its way through. If you do get a broken slate, there is no secondary barrier.
Slate & Resin Interlocking Slates
These where first introduced in the mid 1980's by Redland, it was called the Cambrian, and to date, is still used. Sandtoft also manufacture the 'Brit lock'. These are made from crushed slate (high percentage) and resins. This making them extremely strong and resemble a natural slate so well, once on, even a roofing expert will have difficulty to tell them apart.
As they are manufactured, they are all perfectly flat. Also, there are many moulds, so the grain (pattern) varies from one to the next. They are priced similar to mid range natural slates but are far superior. They have stainless steel clips and nails, clip at bottom, nail at top. This making them almost impossible to come loose. They cover slight humps and bumps in roofs due to the excellent fixing method. There is also less weight to consider, as they are half the size of a natural slate. Finally, the labour costs are less, as you can get them on the roof quicker, and as everyone is identical you dont need to check them prior to installing for imperfections.
Clay Plain Tiles (Rosemary)
These have also been used for hundreds of years. In the mid 1920's clay tiles (in this country) where more difficult to source. Mainly down to the post WW1 housing boom in London (This is why the concrete tile was introduced).
There are still many roofs with clay tiles that have survived hundreds of years, but many don’t make the grade. Unlike slate, clay tile life expectancy depends on how they where manufactured. Also, many clay tiles do not fair well in freezing temperatures. As rain, then freezing temperatures can sometimes damage the clay tile.
Nowadays, plain tile roofs (clay or concrete) are mainly found on prestige homes due to material and labour costs.