Construction Flat Roof Joist Layout

The construction of the flat roof is similar to that of the timber upper floor.

Construction flat roof joist layout.

Joist is a term used in construction for load bearing planks that run horizontally or nearly to horizontally to ground. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. Can i turn my flat roof into a roof terrace. Let s consider a basic gable wood roof framing design.

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. Continuing on from part 3. Attached flat roof 6a cont w. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial.

Here we have a wood framed gable roof. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. In most cases an existing flat roof will be used to create a roof terrace. Flat roof joist calculator.

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. Maximum purlin spacing ro. 1 enter joist details 1 1 span and joist spacing. Add the plywood once you ve added the framing it s time to add a layer of 5 8 inch plywood sheathing.

Of course you don t need to live in a modern house to deal with a flat roof. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths. Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof.

The 8 step process for diy installation step 1. Drawing legend attached flat roof 6a. Instead a pair of beams rest on supports called sill plates to create a frame for the deck. Roof deck framing unlike for decks at ground level doesn t entail a ledger attached to the rim joist of a house.

Frame the roof one important and perhaps not so obvious fact is that a flat roof is not actually flat. 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. Span tables allow for a maximum allowable overhang of 25 of purlin spacing p or 600mm. Structural calculations for timber joists timber beams glulam beams flitch beams using the latest design codes.

Suitable for uk building regulation approval. Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.