Parapets Capping and Windows Sill

Parapet is an extension of wall at top roof, balcony, stairs or a walkway, used as a guard rails. As the parapet function is guard rails, then it hasn’t been less than 80 cm. or it has to install handrail over it. Parapet is covered with capping to protect plaster, stone cladding, curtain wall or any other wall finishing material from water leaking. For same reason windows sill is used for the bottom side. The windows sill and parapets capping could make in different details and from different materials. This post will discuss capping and sill materials, details and recommendations for well installation.

Parapet capping for flower box, made of Palestinian marble, Gaza 2020
Parapet capping for flower box, made of Palestinian marble, Gaza 2020

Design Details

There are several design details for parapet capping and windows sills. There are different designs however they all have the same functions. Here we will introduce some of the parapets capping and windows sill design details.

sill and capping types : straight, round edge, double edge, round double edge, By Zahi Alrayyes 2020
sill and capping types : straight, round edge, double edge, round double edge, By Zahi Alrayyes 2020

Straight: simple but need to chamfer the corners to make the sharp edges safe.
Round edge: for better appearance and for classical style use a round edge capping and sills.
Double: for larger scale use double marble pieces to have thicker sill. This suite residential and commercial modern buildings.
Double round edge: for lavishness or large scale, use double round edges, it has extra cost than previous choices. Typically used for villas and high quality residential buildings.

Double marble emperador meduim sill
Double marble emperador meduim sill, Gaza Alhelou Station 2018

For classic style sills, designers creating several marble edges finishing design, as shown in the following photo. Either straight or round edge details will give a classic style. Round details is more classic however using straight edges with more details will have lower cost and classic style.

Dark Emperador marble stair parapet detailed design classic style, Gaza 2018 by Abu-Qoussay Dbabesh
Dark Emperador marble stair parapet detailed design classic style, Gaza 2018 by Abu-Qoussay Dbabesh

How to Select the Capping and Sill Materials 

Parapet capping and sill material has to have a low water absorption ratio and to resist weathering. So marble, granite, aluminum and concrete are suitable materials to use. 

Marble is a suitable material for parapets capping and windows sill. Select marble with low water absorbing ratio, also order pieces with more length to have fewer connections between marbles, usually it cut into 150 cm length. The connection will be filled with cement or marble adhesive. Marble is cheap, easy to install and to decorate. Marble effecting from weathering, marble veins and pores will enlarge. Tiny veins will allow water to enter through the marble sill and capping. This problem fixed by either filling the pores and veins by cement or marble adhesive.

Marble capping has defect veins and pores from weathering that accrue water leaking, Gaza 2020
Marble capping has defect veins and pores from weathering that accrue water leaking, Gaza 2020

Granite has low water absorption ratio and can resist weathering more than marble. But usually granite colors are dark and light colors have a high price. Also granite doesn’t have many pores that’s perfect with water absorption but cement mortar won’t bond well it. Therefore there are some chemical products we use for granite backside in order to make it rough for better bonding with mortar. This problem appears more after installing fixtures over the granite sill and capping, like handrail. Where opening a hole in granite after installation or even screws will shake the sill and disassemble it from cement mortar. Therefore we recommend to open holes in a method that won’t shake the sill and capping like, water jet.

Double round edge from Rosa Betta marble, Gaza 2020
Double round edge from Rosa Betta marble, Gaza 2020

Mosaic and terrazzo is a white cement material that cast in place. This will give more bonding to the parapet capping and sills. In my view point it looks nice when it has a light large stones like Perlato size 5. Mosaic and terrazzo is cheap comparing to marble and granite. Also it fit stairs and curved parapet. Long length sills requires expansion joint, it’s made from glass as shown in the following photo.

handrail parapet capping from mosaic, by Almamoura Company, Gaza 2020
handrail parapet capping from mosaic, by Almamoura Company, Gaza 2020

Installing Parapets Capping and Windows Sill Recommendations:

  • Install parapets capping and windows sill after the block works, and stone wall cladding and before plastering works. Paint the sills with lime and sand to avoid cement stick to marble during plaster and painting works.
  • Sill size, for width leave a cm or two for plaster works thickness, and leave 3 cm for tiles works. For the outside, leave two more centimeters to have a cantilevered sill. The cantilevered sill will allow water to slide away from the walls to prevent water dripping the wall. Also prevent water dripping by a grove in the bottom surface of the sill or capping. 
  • The capping or sill length has to be straight leveled. For the width make few millimeters slope toward the outside to allow water slide outside instead of leaking.
  • For corners use 45 or diagonal connections, they look nice and will bond together better than any other connection.
Parapets capping corner connections, Gaza 2020
Parapets capping corner connections, Gaza 2020

FAQs

What capping to use for curtain walls?

For curtain walls and aluminum composite panels  facade use aluminum capping. Aluminum capping can be done by a certain profile or customized from ACP. Remember capping and sill function is to prevent water leaking and the material has to prevent weathering, then aluminum is perfect.

Palestinian Stone

Palestinian stone is located at West Bank Mountains. Also it’s called Jerusalem stone and marble, with average annual sales of 600$ million. Commonly it caved in a rough texture to use in building facade cladding and for decor. The Palestinian stones and it unique rough texture is a main character of the Palestinian architecture.

As Palestinian stones are limestone extracting from different mountains. Thus stone types are various according to location. Each stone has it physical specifications, where they vary in absorption ratio, rigidity and strength of bearing, leading to price differences. Most famous stone types are Njassa, Shyoukh, Slayeb, Tafouh, Barezit and many others.

Palestinian stone types

Njassa and Shyoukh are white. However Njassa is more white and has less absorption ratio which will remain white for longer type. In other hand Shyoukh Band 160 found deep inside the mountain, which is similar to Njassa stone specifications. Slayeb is red and yellow stone, its solid with a low absorption ratio. Taffouh is that yellow stone, while Birzeit is varied from yellow to grayish green but it yellow is more hue than Tafouh. There are other types found in Palestine like Beersheba stone in Negev desert. Its light gray color stone in similar tones, this gives architecture seem like it built from one stone building.

Palestinian Stone Extracting

Stone extracted then cut in slabs then to different sizes and thickness to fit the required application. What’s makes Palestinian stone unique in facade cladding, its has a rough face where it shows architecture massive. The well-known two major sizes, the 25 cm height and 12 cm height its come in 3 cm thickness and random widths. Personally I consider 12 cm height is more beauty in scale and details, however 25 cm scale and details appear differently because it requires a different caving techniques. Increase stone thickness could be a solution to have the large size appears in nice details similar to 12 cm stone size.  

Palestinian Stone and Water Absorbing Problems

Palestinian stone as limestone has a high water absorbing ration. Specially that rough Palestinian stone surface is not treated for water absorption. The stone will yellow and convert to black color that have a bad appearance and could easily noticed. There are a few tips to take in consideration to avoid yellowing.

First and most important to fix water leakage problems. Most usual problems happen in slab connection, where problems with indoor plumbing that affect the elevation stone cladding.

Also inverted beams around the building boundaries will prevent water to reach the Palestinian stone. The inverted beam has to be casting with slab to avoid water leakage. Another thing is to avoid installing water supply pipes at floor, and install the pipes in the false ceiling. In the false ceiling the problem will appear immediately, unlike floor installations. The cost of removing the false ceiling to fix the pipes is smaller than removing floor tiles for pipes maintenance.

Second tip is to temporarily connect stone together, use marble adhesive. Some craftsmen use gypsum to temporary connecting, but gypsum is organic material that wouldn’t stay for a long time. Then the place of gypsum mortar will be a gaps to collect water. The marble adhesive is better choice for traditional installing method – the casting -.
Stone types, cut sizes and arrangement have various alternatives, resulting huge methods to build and design of the building facade. Here are some photos of buildings elevation designs that created by Palestinian stone.

Palestinian stone joints

Rough Palestinian stone, use a wide joints that fills with cement grout. The nice width for the rough Palestinian stone is 7 mm. Where craftsmen use grinder to wider the joints. The grinder will straight the joint and give them the same thickness. As the joints between the stone tiles are wide it requires adding sand to cement grout. Sand will make the mixture rigid, rougher also sand will color the mixture. For white stones like Njassa, Shyoukh use white sand like sea shore sand to prevent yellowing the mixture. After filling the cement grout craftsmen use steel brush to clean the joints and after use grinder steel brush to clean the stone surface. For colored Palestinian tones like Beirziet, Slayeb or Tafouh craftsmen add pigments to color the grout. 

Palestinian stone Njassa 25cm height using traditional installing-method
Palestinian stone Njassa 25cm height using traditional installing-method. Gaza 2017

Palestinian Stone Sizes

Stone types, cut sizes and arrangement have various alternatives, resulting huge methods to build and design of the building facade. Here are some photos of buildings elevation designs that created by Palestinian stone.

building using Slayeb stone , Gaza by ORIGIN DESIGN
Palestinian stone by ORIGIN DESIGN
Proposal for Palestinian stone building in Gaza using rough and smooth stone.