Building Extensions - Please advise

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We will be doing a two extensions:

1. A 2-storey extension on the front of the property with a loft conversion on top of this (the roof of the existing property will be replaced to have one big roof space).

2. The other will be a single storey rear extension with a flat roof.

Would it be possible to make both of these extensions with wood (i.e. treated pine and OSB/plywood inside and out (is any one of these better than the other) and then spray foam insulation (to act as both insulation and a vapour barrier).

On the back extension we would want to put folding, sliding doors and render and on the front we would like to put an outer skin of bricks to match the existing frontage.

Is this possilbe? We know that houses can be made of wooden panels but not sure whther you can addd them to a brick building. Cost is an issue and we were wondering whether they can be made onsite or whether they need to be factory made.

Any advice much appreciated!

Thanks! :)
 
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Yes you can construct these from a timber frame.

Depending on the insulation used, you have either a 90 or 140mm timber stud wall, plaster board on the inside and then the external is clad with a suitable skin - eg timber cladding or a brick skin

You can make the panels up in your garden and just assemble them togehter
 
Thanks Woody ... that's great news!

Is there anything we should watch out for re building regs or is it simply a matter of building the walls flat on the garden and then fixing the panels to the foundations and the existing external walls?

With regards to the 2-storey + loft extension, does this need to be made of thicker timbers to take the weight especially on the ground floor or would 2 x 4 or 2 x 6 do the job. We are happy to use thicker timbers so we can use a thicker layer of insulation.

Thanks again! :)
 
Basically, you make up the panels in 8x4 sheets and fix these together in a modular fashion.

Ground and first floors are the same panels. No need for thicker timber

Loads are transfered vertically down the struts, so you work on 600 or 400 centres. Timbers are doubled up around openings too.

Sound thermal insulation are considerations so choose insulation to deal with this.

The main concerns with this construction method are to maintain fire resistance and vapour control of the structure. So attention to DPC's, membranes and maintaining integrity around services and openings are very important.
 
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Woody thanks again!

Can you recommend somewhere i can learn/read more about this, especially re insulation, vapour barriers and DPC? Also, about recommended products and best practices, e.g. to prevent wood rot, when fitting services, etc.

Thanks :)
 
You wont get any better than this book from TRADA

For insulation , many local authorities publish guidance notes. Search your LA's web site or neighbouring ones
 
Cheers Woody ... the site has a sample of the contecnts ... its pretty involved! :)

BTW would specialist builders be neede for this (i'd like to do some of the work but don't know my limitations) or would any builder be fine?
 
Its not really a specialist job, but whoever does this must be experienced in the concept and mindful of the precautions needed.

The building inspector wont check every little detail or the quality of the work, so there has to be either confidence that the work is being done correctly, or additional checks done to ensure that it is
 
Also, the BRE good building guide GBG 60 (2004), gives an excellent introduction
 

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