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- Frequently Asked Questions about the Cotswold Stone Roof -
Who produces the materials?
Manufactured in the UK by a division of Aggregate Industries Ltd and marketed under the Bradstone brand.
Aggregate Industries, founded in 1858, has over 60 operations in the UK, employing over 3500. Aggregate Industries Ltd is a member of the Holcim Group, which operates in 70 countries, employing over 72,000 with a revenue of 26.7 billion.
Fun Fact: If you combine all the Clay, Concrete, and Slate manufacturers in North America into one company, it would be smaller by size and revenue than Aggregate.
What are the stones made from?
All Conservation and Old Quarried Stones are made from concrete. Concrete is the perfect material to work from when casting materials of this size and finish. It allows us a high level of detail, the various extra large sizes we require, and can produce a colour range closer to that of natural stone. Mixing and production are all done in-house and are computer controlled to insure the highest level of quality.
20 years is impressive, but how do I know how long it will last?
Testing against a standard. The material is produced to the highest level for the UK and European use. Those standards alone would be sufficient, but we test here in the USA at an ASTM lab certified for the US standards. The expected life of the material is 65-75 years, depending on location.
How long does it take to order a roof?
Most roofs will be produced in 12-14 weeks. Larger projects will take longer but will be produced so that material can arrive on-site and installation can begin.
How long does shipping take?
Depending on the port and how busy the ships are, it can take up to 2 months for materials to travel from the UK factory to the job site. We take care of all freight and importation procedures. Those costs are built into every quote.
I’ve never worked with this type of roof do you offer training?
We do one better. We provide a booklet for each project which outlines the technical details for each section of the roof. It covers the installation exposure for each course, graduations, special stones, snow retention, and any other detail found in that section.
How does Cotswold Stone compare to slate?
The two materials are very similar and will feel immediately familiar to anyone with slating experience. While there is no time-consuming grading and sorting with a Cotswold Stone Roof, it has eave course stones, defined graduation, and a short top course. The materials can be installed directly on the roof deck or using horizontal battens.
Can the stones be used in earthquake or fire zones?
Absolutely. The materials are non-combustible and thick enough that they will dramatically reduce the radiated heat from a fire protecting the structure.
Why are some roofs installed on battens?
Battens or the horizontal wood lath are used to support the stones off the roof deck. This can be done to stop the roof from radiating heat in hot climates directly to the house by providing an air gap. To allow the roof to move under the weight of ice and snow in high alpine conditions. It can also be done to increase the efficiency of the installation as some of the stones have nibs that can hold the tile in place by resting on the batten.
My client would like a custom roof.
Each custom request will be reviewed upon request. Call or email for further information.
What does a roof like this weigh?
The information here is the basic weight of the stones. It does not include any of the materials that are required for installation. All weights are based on 1SQ = 100SQFT
Conservation Cotswold ( 2400lbs per SQ )
Old Quarried ( 1850-2200lbs per SQ )
What is "graduation"?
Graduation is a term used to describe the transition of sizes of stones as they progress up the roof. With most graduated roofs, you will have three or four lengths of stones, the largest at the eave ( bottom ) of the roof and the smallest at the top. Each length of stone will have 6-8 different widths of stone to create a random look as they are laid.
What is efflorescence?
Efflorescence occurs naturally in almost every stone, from slate to blue stone. Sometimes called "weathering," it also can occur in concrete-based materials.
When moisture from rain, condensation, or dew penetrates the pores of the stone and carries calcium hydroxide, which is formed in concrete during the hydration process of the cement, to the outer surface of the concrete, the water then evaporates, leaving a white film, on the surface.
The efflorescence, while at times unsightly, is superficial and in no way a defect or affects the quality, functional properties, or structural integrity of the concrete. As with any natural process, we recommend that it be left to run its course. Over time the calcium hydroxide will be depleted, and the natural effects of weather on the roof will remove the marks.
I live in the UK. Can you help me?
Being based in North America, we don't work with UK and European clients. We're happy to refer you directly to the people we source our materials.
Feel free to reach out to us with your material needs, and we'll get you in touch with the people who can help.