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

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.

How to buy aluminum sliding windows

Secrets to buy aluminum sliding/gliding windows. Aluminum opening systems made to fit different building designs, therefore the alternatives are wide, there are many choices and cases. Different products may look similar, but quality could totally different according to system specification. This article discuss aluminum sliding systems’ specification in FAQs type to get understanding of aluminum sliding system and how to check quality.

sliding windows , Gaza 2018
sliding windows , Gaza 2018

How to select Aluminum Sliding Window?

Why using aluminum for openings?

The aluminum material is formed into profiles to complete aluminum systems for openings. Aluminum does not affected from natural factors like sun and humidity, therefore aluminum systems customized to prevent water and wind leakage. Another benefit to choose aluminum because it easy to customize and install aluminum opening, compared to wood, steel.The beauty of the aluminum appears in its straightness profiles and the wide variety of paint options either by color or texture.

What is aluminum material types?

Aluminum is alloy contain several materials, the difference of material percentage and manufacturer process result several aluminum types. Alloy systems are classified by a number system (ANSI) or by names indicating their main alloying constituents (DIN and ISO). Selecting the right alloy type for a given application entails considerations of its tensile strength, density, formability, weldability, and corrosion resistance. You can test a sample in lab to ensure the quality of aluminum alloy.

Aluminum is waterproof?

Yes Aluminum is waterproof, but the aluminum sliding windows is not aluminum only. Window contain other materials like glass, sealers. Installing methods is an important issue, selecting the right aluminum profiles,the place of holes and accessories are taken into consideration.  
Read “Aluminum Windows Water Leakage Problems” article for more information

Aluminum profile can accrue water leakage?

Yes, Since sliding window has a roller and rail at the bottom means there is an empty place, that allow water to enter indoors. This requires a small holes toward outdoor to allow water to slide away. Wind direction may not allow collected water to slide away, therefore it requires accessories that allow water to slide out. In the case of heavy rain, small openings can not get water out at the required speed, which may leak rain inside. As a solution for that aluminum companies develop a lower profile that have container underneath the rollers rail to accommodate the largest amount of water away from the roller rail.
Another thing to take into consideration that low thickness of aluminum can affected from heavy wind. Aluminum will bend and become hard to open and close, and it may accrue water leakage.sliding windows rails, Gaza 2016

ًWhat to fill between aluminum and wall?

Filling between the aluminum and wall require a material to fill and prevent water, wind and insects. Filler by auks sealers, divided into three main types: Acrylic, Silicone and Polyether.
Acrylic use as indoor filler, moisture affected it and it will collect bacteria. In other hand Silicone is indoor filler, but it’s an antibacterial product, which is transparent and can be customized to any color. The problem facing silicon is to connect with wall where it’s designed to indoor usage only. Polyethers products like SikaFlex made in Switzerland, it’s made for outdoor usage, it can resist the natural factors affect the filler. 

What type of sliding window roller?

First of all, rollers run over rails, these rails are available in plastic easy to break, therefore aluminum rails is better. There are several rollers types, single or double roller, and depend on how many K.G. it designed to load. Important aspect to understand for window panel, the ratio between height and width. Narrow panels will not open easily because it’s accrue bending moment during opening.

What are window panels types?

Basicly the aluminum profile depend on the thickness of the glass. Normally we use 6 mm and for large opening 8 mm. Notice that glass has high heat transfer coefficient, as a solution we use double panel glass. A two layers of glass and air in the middle, the static air has a low heat transfer coefficient. To improve this technology there is triple glass, made of three layers of glass and static air between them. For more information about glass sheet types, check  Glass Sheets types topic.

What are aluminum painting types?

For more understanding of aluminum painting types check Aluminum painting types topic.

Conclusion

It’s hard to select Aluminum Sliding/gliding windows, you need to have many information about producers. Also aluminum has many secrets than what we mention above. Keep always up to date and feel free to ask any question.