Loft Conversion - Structural Calculations

[maxantax]

Dear all,

I have a question regarding structural calculations for a loft conversion.

When converting a loft the original structure supporting the front half of the pitched rood is essentially left in place (except for the purlin replaced by the dwarf wall). Below is a typical detail.

My question is: how much of the weight of the front slope is supported by the new ridge beam and how much is supported by the existing structure?

Is there a rule of thumb / industry practice when doing these calculations?

Many thanks,

Max

Ridge Detail

• maxantax
• 18 Feb 2015
• 1

Schematic Design of Ridge for Loft Conversion

 

[jeds]

Calculate the loads on plan by square metre but allowing for roof slope. e.g. one square metre of roof at 45° pitch is 1.4m on plan. Do a sketch of the roof plan and mark the load points. i.e. this is where the load is taken to. In a simple beam supported at ends, 50% of the load goes one way and 50% the other. A roof is treated exactly the same. Once the loads are calculated as above you ignore the slopes and distribute the loads on plan.

 

[Nakajo]

I hope we're talking in hypothetical terms here. Obviously, you wouldn't start any actual work until your calculations had been verified by an appropriately insured structural engineer.