Bottom one is bigger but simple and straight across the back, however you have works around the existing bedroom 3 to contend with.

Top one is smaller but no mucking around with bedroom 3 however this one juts out so a little bit of mucking about here.

Probably the top one is cheaper and easier.

Builders would make frames on site and also pitch the roof on site.

Being old means the existing walls are probably out of square so joining old an new needs to be nutted out on site.

Thanks MB - I just added a photo which shows a bit more clearly what's going on, and here's another view of 'bedroom 3' in its stripped-down glory . Good point about needing to make the frame butting the existing house, on site

Hey MB, thanks for the comments! Regarding the pitch of the existing roof over Bedroom 3 - this was built in 1940 to the codes at the time, but the pitch of this roof is around 3 degrees and does not meet the requirements for corrugated roofing pitch of 5 degrees. So in terms of matching this, I'm wondering about using a different roofing profile - say Kingspan, with 450c purlins - at 3 degrees, and to flash it under the existing corrugated roofing for the extension. I know it won't look too pretty to have a change of roofing profile, but my budget doesn't extend to replace the whole roof . Thanks for any insights...

Yes thats correct, use Monodeck, Longspan, Speed Deck, etc. for the lower pitch.

We do them this way all the time and being a low pitch the profile is hardly noticeable.

The tricky part is ensuring the waterproofness between new and existing.

HI MB great to get the confirmation, thank you.

I've just come up against another issue in regards doing the whole extension as a slab - it basically will keep a continuous damp patch up against this old house (plastic membrane) which will damage the existing old bricks. So I will have to install sub-floor ventilation into the existing space adjacent the new extension. The best way to do this will be to add a whirligig to the roof and run a pvc pipe through the wall to ventilate this space. I may also add a 90mm cavity wall to the kitchen (on the other side of the wall in question) and add the ventilation pipes through this. See diagrams. Having a false wall in the kitchen will also help me to fix kitchen overhead units to it, as the fake wall will be able to carry some weight - so win-win I hope :-)

Subfloor ventilation is quite poor in older homes unless they're open - up on piers and open sides.

When we renovated and extended our place we installed an electric subfloor ventilation fan to existing. This runs continuously and has done for a few years now. Uses little electricity as well. Extra brick vents were also installed but the electric fan really forces the air movement.

As we're on a site that slopes down from street, being on a sandstone shelf with little top soil as well as no street gutters we used to get quite a bit of damp from seepage. This then made the subfloor quite musty. This has now completely gone! Even after solid rain for a few days the soil is still quite dry, it quickly drys again if a bit damp.

Could be worth considering compared to whirly birds/plumbing to install. Electrician to install a new power point and I cut bricks and fastened the unit in place as it uses a standard plug and lead.

I'am no Pro, but was wondering what the difference in cost would be to use a liveable shed, it would be a seperate unit with 3 walls, 1 made up of your existing windows, racked ceiling and must be black, my favourite liveable shed,and lined with ply wood.

Hi Souzette

Great to see that you've gotten started... can you answer a few questions please?

Firstly, have you had any planning/permit approval? The demolition and commencement of footings requires certain things in place.

Also;

• have you isolated the power to the old room and demolished section? I see bare wires hanging through the framing to bed 3
• Was that a toilet and laundry that was demolished? Has the sewer been capped where the old toilet waste is?
• Can you give some background as to what you've done? eg have you had the block surveyed?
• Also, can you please upload a pic from the back door looking out to the yard, one looking down each side and some close ups of the perimeter of the existing slab/existing bed 3.
• What is the site access like?
• Who drew up your plans?
• Are they the footing dug out in the photo?
• Has an engineer given you a design for them?

The reason I ask about the plans are that from what I can tell in your pics the walls are 32 courses? Has anyone drawn an elevation for you (so you can check eg ceiling heights as I don't think you'll stay at 2700 over that span)?

Regarding the slab, if properly isolated from the existing slab I don't see any damp issue to the existing brickwork unless there are other site conditions?

This is quite a straight forward build, but in truth I'd probably lean more to getting rid of that existing room unless you are happy with it as it is eg window locations/old door etc. You are probably going to have to re line the interior anyway along with the exterior.

I can't stress enough though that before you go too much further there are some things that (if not already done) need to be resolved or would be helpful if you could provide feedback.

If I were doing this extension, I would be laying a concrete slab. Without knowing locality, your engineer will provide a spec and design to allow for clay? subsoil, and footing size and reinforcement.

I would be framing up the entire extension on site and would only be employing a chippie to do that. If this is how it was being built, the engineer would also provide the structural diagram specifying the beams and columns (if any) and their location. This would take into account the local regulations and compliance for eg uplift as they will provide tie down details etc.

A light weight roof is fine but again this needs input from the engineer.

Once those items are resolved, and you have your approvals, the process is quite linear.

Cheers

Not knowing what stage you are at except for the photos and other internal works.

I love liveable sheds, OK Louise is just in the process of completing her country retreat.

The following link is not for style but gives an idea of costs and what can be built as pre approved by council in NSW.

http://smartlookingsheds.com.au/home/4591568742.

HI Siriuskey - I see what you mean now about liveable sheds, and I love them too. Im planning to put one at the back of this site, attached to a garage. But it's a good idea to see about this for the extension - I'll send a quote request now, great idea :-)

actually...$30K for 4m x 3m + verandah seems rather pricey, but the concept is good

There's a beautiful example of a (black) liveable shed in Bowral, a well known lady who already owned a property with a brick cottage added a liveable shed to accommodate herself and the old attached cottage was for family. Look forward to hearing what kind of a response you get and if I can remember the ladies name!!

HI All - for some reason my lengthy reply a few minutes ago was deleted :-(. I put so much thought into it! So here it goes again. Basically a big thank you to you Houzzers.

MB your subfloor ventilation sounds great and Im glad it's fixing the problem so simply. The reason why Im trying for a whirligig solution is that I favour a passive system, however if it doesn't work I'll look into what you suggest

Siriuskey - yes to some kind of kit. I've already contacted a guy on Gumtree selling grannykit frames - he says for something to my specifications would be about $4000 for the steel frame alone. Would need to check engineering details - and the liveable sheds you've linked me to seem to have that all checked. Although getting a local Chippie to frame it all up on site - as Twos Co suggests - is probably the most economical option

Two's Co - thanks for the feedback and the excellent checklist of processes. I've covered most of the concerns though - I've got the DA based on my own flimsy plans. Because it's relatively small, I was going to work with the builder directly and over-engineer it. I've since engaged an architect to do some handsketches and draft specs, which will be signed off by a structural engineer. It's basically a portal frame independent structure, with a 3 degree pitch skillion roof.

The house was rewired and the wires you can see are non-live looms waiting for the extension! The sewer is not connected and that part was never plumbed in. There's good rear lane access, but for the purposes of getting concrete in, I'll most likely get a concrete pump from the front of the house - for $180 per hour they will save time and make the concreting much easier. The existing trench I got dug in because I had an excavator on site installing those lovely large concrete blocks you can see, for the retaining wall (500kg each). But that was 7 weeks ago, and the excavation has got too large, and I worked out for a very similar cost I can make the extension 1m wider, so why not. The existing trench I can fill in with the demolition rubble, compact, and filled with any fill waste.

Two's Company, I'm on the fence about removing the existing Bedroom 3. If I thought it wouldn't add to the costs too much, I'd do it. One advantage is that I could then make the whole 9m long extension (Option 2) around 150 - 300mm higher, (ie a step up from the existing house) and thus avoid too much excavation and a potential pond. To answer your question about damp and moisture, the whole house is facing a hill with 7 degree slope, and fixing this has been the main aim of the retaining wall, however the runoff is only likely to increase in coming years.

anyway here are a few photos. The site is still so messy because the demolition only happened 2 days ago - Im still tidying up....

Robbie W,alker of MEB, this similar to what I had in mid for your extension, with the roof pitch running in the other direction this could be the new extension less the 3rd bed, I think a livable shed would work beautifully, there are many Co's that do them

https://www.lunchboxarchitect.com/featured/glass-link-house-robbie-walker/