Construction Flat Roof Joist Layout

1 enter joist details 1 1 span and joist spacing.

Construction flat roof joist layout.

In most cases an existing flat roof will be used to create a roof terrace. Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof. Span tables allow for a maximum allowable overhang of 25 of purlin spacing p or 600mm. On a basic level flat roof construction comes in the form of roofing timbers or joists as they are more commonly known or steels that are laid across two uprights walls in most cases.

Structural calculations for timber joists timber beams glulam beams flitch beams using the latest design codes. The 8 step process for diy installation step 1. Yet for historic modern style buildings like this old house s cambridge tv project flat roofs are at the core of the architecture meant to reflect the broad horizontal lines of the natural landscape. Joist is a term used in construction for load bearing planks that run horizontally or nearly to horizontally to ground.

Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. Continuing on from part 3. Add the plywood once you ve added the framing it s time to add a layer of 5 8 inch plywood sheathing. Maximum post spacing maximum rafter spacing maximum purlin span p.

Instead a pair of beams rest on supports called sill plates to create a frame for the deck. If you have a low sloped roof or flat roof of less than 2 in 12 these evenly spaced planks will be called roofing joists. The steels or rsj s rolled steel joists are often built into one or both walls to give added stability to the roof structure. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading.

Drawing legend attached flat roof 6a. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. Maximum purlin spacing ro. Let s consider a basic gable wood roof framing design.

You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths. The construction of the flat roof is similar to that of the timber upper floor. Attached flat roof 6a cont w. Floor beam span tables of residential structural design we will now look at roof rafter and beam design.

Frame the roof one important and perhaps not so obvious fact is that a flat roof is not actually flat. Flat roof joist calculator. Of course you don t need to live in a modern house to deal with a flat roof. Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.

Can i turn my flat roof into a roof terrace. Suitable for uk building regulation approval.