Welsh Slate Window Sills 4
Welsh slate window sills, heads and reveals
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Slate Window Sills

Grey slate and stone ltd specialise in manufacturing made-to-measure slate window sills. Made from 100% natural slate we cut and machine slate to make window sills to your specific sizes, each project will have its own unique aspect with its own profile and specification. 

Our company is dedicated in delivering the product that best suits your project at the best price guaranteed. 

On this page you will find various options that best suits your build including a custom form for you to contact us with your project detail, so we can get a better understanding of your requirements.


Profiled Slate Window Sill

Profiled Window Sill

Profiled slate window sills are manufactured from the highest quality slate. 

This option has a weathering detail that will allow the window to sit on top of the stool, its sloped front and fluted drip will prevent water from entering your home.

Plain Straight Window Sill

Plain Straight Window Sill

Plain straight window sills is a cost effective solution to our profiled option. 

To create the fall required to repel water we advise bedding the window sill on a slope this and the fluted drip will prevent water from entering your home.


Horns or Joggles

This illustration of how the slate sill will look with joggle cut in to the slate window sill. Render is then wrapped around the window sill for extra protection.

This option looks great but is not required by building regulations.

Our Slate

Grey slate and stone ltd manufacture window sills from the finest quality slate. We have three options from our popular Welsh slate to a more cost effective Mont black slate range all have their own appearance and cost.

Welsh Dark Blue Fine Rubbed Slate Window Sills (Cwt Y Bugail Quarry)

Custom made to your sizes available in a honed, fine rubbed and textured split finish.

Welsh slate window sillsWelsh slate window sills cut with joggles ready to be fitted

Mont Black Fine Rubbed Window Sills

Made to measure window sills available in a fine rubbed finish

Mont black fine rubbed slate sillsMade from the finest slate available in long lengths

Profiled or straight

Our slate window sills come in two types: profiled and plain straight option each product is available in thicknesses from 30mm 40mm and 50mm with other thicknesses on request. We recommend adding an overhang on front edge of 50mm this will allow enough overhang to accommodate a drip 6mm groove this will prevent water from returning to your wall.

Sizes & Edge Detail

We specialise in manufacturing slate window sills in various lengths and widths. We can cut with in reason your window sills to your opening sizes, with a choice of edge detail from bevelled, pencil round to half round. 

Fixing & Joints

Our slate should be fixed with a traditional sand and cement mortar bed, we recommend that a slurry mix should be painted on the back prior to fixing this will allow the slate to bond to your wall safely and securely (see slurry mix method).

We recommend that each piece should be fixed with premium silicone like OTTO Seal S70 in either a anthracite or black colour, it’s a natural stone silicone guaranteed not to cause any migratory staining on natural stone with excellent weathering and ageing resistance. Suitable for use outdoors and UV resistant.

Standard Sizes

As well as our made to measure window sills you can now purchase standard slate in regularised lengths and widths, with one long edge fine rubbed and bevelled we have also included a drip groove to the under side of the front edge this is all included in the cost ready to be purchased and delivered.

Contact Us

Quality, price and customer care is very important to us if you would like to discuss your project then please don’t hesitate in contacting us, we are dedicated to helping you with your inquiry. 

Tel: 01766514700 Contact Us


Window Slate Sills

Slate window sills are bespoke made to order. For bespoke made to measure slate window sills we do require window opening sizes, this can be taken off your Architects drawing however we recommend a site measure before we manufacture.

Standard sizes are also available at more cost effective prices.

Please select what type of slate you are interested in
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