Change Conservatory to Extension

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Lancashire
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I am looking to change our current conservatory into a extension, can someone help calculate some rough costs please?

The size is 6m x 4m

Two of the walls are already attached to the house, so I am thinking if we remove the conservatory and two dwarf walls, then take out the footings and put in the depth required for the extension. We are then looking to have full height windows to the roof and then either a GRP or Rubber roof on top with a lantern or flat Velux window. I am just not sure how the windows will support the roof, any suggestions?

I am purely trying to calculate the basic cost, ie footings, roof etc as I already have a good idea of window and door costs.

Hope I have not missed too much,

Thanks
M
 
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I am looking to change our current conservatory into a extension, can someone help calculate some rough costs please?

The size is 6m x 4m

Two of the walls are already attached to the house, so I am thinking if we remove the conservatory and two dwarf walls, then take out the footings and put in the depth required for the extension. We are then looking to have full height windows to the roof and then either a GRP or Rubber roof on top with a lantern or flat Velux window. I am just not sure how the windows will support the roof, any suggestions?

I am purely trying to calculate the basic cost, ie footings, roof etc as I already have a good idea of window and door costs.

Hope I have not missed too much,

Thanks
M

It sounds like you are removing the conservatory and foundations and starting from scratch?

if you want a permanent opening between house and extension you will need building regs.

if you have windows to ground on 3 sides you will need wind posts at the corners, cast onto foundation for lateral support.

you can do either steel, timber, glulam beams for the perimeter.

We use glulam beams, 66 x 315 or 90 x 315 for the perimeter. Then 90 x 405 for the H arrangement to support the lantern. The 405 is cut down to 315 at flat roof perimeter. That sounds like a deep beam, but it allows for 150mm ceiling joists, 11mm osb, 25mm firrings (lowest point), 120mm or 125mm celetex.

be careful to find out the size of windows, upvc has strict max sizes as does aluminium. Timber can have quite tall windows or can be doors.

as above said 30k-40k for upvc. Timber more like £75k

If you want something nicer than standard upvc look at flush timber alternative windows like residence 9 and have timber posts and fascia.

if you want an external gutter then look at a flush ogee style (MOG2) from guttercrest or similar.
 
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Have you dug alongside the foundations? I have nearly the same project and found a footing deep enough to satisfy the BCO
 

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