How to Estimate Deck Railing

DekPro Prestige in Cocoa Bronze installed by Jason Davis in Spring Hill, KS

Ordering something like Deck Railing online can be a daunting task; and when faced with different railing products, it can be difficult to know just what you need. In this article, we'll take a basic deck design, label and list the aluminum post placements, and decide the sizes and quantities of railing kits to order. To do that, it is important to understand what lengths and sizes are available.

For this demonstration, we will be using Prestige Rail by DekPro. Prestige Rail (shown above) has a calm curved top handrail, with railing kits in sizes of 6'x38", 8'x38" - level and stair. Also available are - 3"x3" Face-Mount Posts, 4"x4" Post Sleeves, Multi-Angle Bracket Packs or "Cut Kits," Lighting and Accessories.

So with that, let's figure how much railing you need for your deck. The first thing to do is make a 2-Dimensional drawing of your deck. Make sure to label the sides of the deck, account for any angles, and measure the total distance of your stairs; from the front of the top stair tread to the front of the bottom or last stair tread step.

2D deck drawing for estimating railing, draw sketch of deck and lable dimensions or measurements to plot posts and rail sections or kits

You don't need to scale the drawing. You don't need straight lines, or for it to look good. We are just making sure we understand the size of the deck and how much railing is necessary to be placed around the perimeter. 

Now that we have a drawing of the deck, we can find where the posts should be placed. Draw a square for each post at corners, edges, and top and bottom of stairs. Then add any posts between those posts for any sections larger than 8'. Rail Kits are Available in 6’ and 8’ Level and Stair, so a section that is 7’ will require an 8’ Rail Kit which will need to be cut in the field before installation. As shown in the illustration, the Stair Sections which are 9’6” total length will require two 6’ Stair Rail Kits on each side and 44” posts between. Now, label the distances between all posts with a 6'L (6'Level), 8'L, 6'S, or 8'S (8' Stair) (Multiple "short sections" under 4', can be achieved by using one longer section (8' or 6') and "Cut Kits" which are 4/Pack Rail Brackets are available in Level, Stair, or Level Angle Adjustable ADJ for 45 and other degree angle turns.

Deck drawing 2 dimensional with post placement and rail kit placement figured

To easily install level rail brackets on level posts, use the Quick Rail Jig, a template for installing level brackets. Level or stair rail brackets are included with Rail Kits, as are balusters and footblocks.

***Side Note for Stair and Level Posts.*** 40" Posts are used for all level rail application, as well as for the TOP of the stairs. 44" posts are available for stair application either in the MIDDLE of the stair section, and/or at the BOTTOM, and allow the post to be placed next to a stair rise with enough height for the stair rail to plane through. Post Kits include a 3"x3" Square Aluminum Extrusion welded to a base flange with 4 holes for lag fasteners, a cover or skirt to hide the lags or screws, and a 3"x3" post cap. Screws are not included with post kits and must be purchased separately. Notice, in the picture below the two bottom posts are both 44", but the top post is 40".

Stair Drawing from the side showing where 40" posts a placed and where 44" posts go

Now, count how many of each Post Kit and Rail Kit you need, along with any additional Cut Kits, whether they are to convert level to level angle, or just turning one Rail Kit into two shorter ones. Also, be sure to add 4 lags or screws per Post Kit. For Wood, Composite, or PVC Decking on a treated frame, use a 4" or 5" lag screw such as Fasten-Master Ledger-Lock, or Simpson SDWS Screws. When attaching to concrete, use a Concrete Rated screw like GRK Caliburn XL or Tapcon. Take the number of total posts ie. (9@40” + 4@ 44”) = 13 Total Posts, then multiply by 4 ie. (13*4)=52 So, we will need 52 screws for 13 total posts. 

List of railing materials for DekPro Prestige Aluminum RailingThe last part to consider is if you want any low-voltage lighting, different post caps, or a Tri-Rail which converts regular Rail Kits into a 3-rail railing. All lighting options, sizes, color profiles, and accessories including ADA handrail can be found in the DekPro Prestige brochure in the link at the end. That page also contains installation instructions, and ability to purchase DekPro Prestige Aluminum Railing Products and Effex Low-Voltage Lighting Products! See DekPro Prestige here

DekPro Prestige in White Textured or Dream White with 3"x3" posts and Tri-Rail 3-Rail

Uncomfortable Doing the Take-Off on your own? Send your drawing to sales@deckandrailsupply.com - and be sure to include the shipping address and your contact information!

DekPro Prestige Black Textured or Absolute Black Railing Attached to Cedar 6x6 Posts Under a Contemporary Perogola

Thank you for reading, We hope to hear from you soon! You can always call us at 913-884-3335