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suetheron_london

Help!! Box gutter + extension question, re-posted

Souzette Lovell
4 years ago

Hi, I posted this yesterday but there was a misunderstanding with the way I described it. I have a very tight budget, and I am designing this with minimal input from a structural engineer and basic details from an architect. I'm looking at getting the frames prefabricated offsite to help manage costs to lock-up stage. I've allowed up to $5K for concrete/footings.

I need to resolve the "connection" between the original 1927 house and a new extension. The extension must be self-supporting and independent of the main house structure. Footings will be excavated 1m from the main house, but the floor will be cantilevered back to the house, with a new timber wall frame butting up against the original house. This new timber wall frame will support the roof structure of the new extension.

My question is in regards to thermal performance of the new extension. The main house is double brick with 3m ceilings - it performs brilliantly in all types of weather due to thermal mass. The extension will be light-weight by contrast. It faces directly west, and faces up a hill. I've salvaged some beautiful bifold windows and doors to take up most of the west elevation, they will open onto the garden of a long block.

I'm concerned about managing solar gain in very hot summers, so want to keep the ceiling high.

OPTIONS

  • The simplest connection between the original house and new extension would be a skillion roof tucked under the original roof rafters, see Image Option 1.
  • Pitching a skillion roof on the extension in the other direction would perform much better, but it creates a large box gutter between original house and extension, see Image Option 2. I've got an online quote for a 1m wide box gutter, 2*5m lengths is under $1000. I'm nervous about a box gutter and for other reasons also.

I'd appreciate any comments and feedback please, about how this can be improved. Especially in regards to a truss system for the roof of Option 2, incorporating pergola timbers. Thanks in advance, and thanks also to Sarah (I think) who made the great suggestion of making a useable gap between the old and the new, which I've now incorporated.


ROOF JUNCTION

OPTION 1 - skillion same pitch


ROOF JUNCTION

OPTION 2 - box gutter





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