Building Extension with Pre-Fab Wall Frames

[zacnelson]

Thanks guys, you've all been so helpful. As it happens RileyP, I do in fact have a tiled roof in the existing house, and I intend to have the extension in colourbond and to replace the entire old house roof with colourbond at the same time. I have a number of reasons for this;
1) I LOVE the look of colourbond
2) 45 year old house, roof needs re-pointing, gutters falling apart, and fascia boards all rotten so large-scale changes required regardless
3) It would be impossible to match the old tiles anyway

I also think that with changing roof cladding, it should make it easier to account for some slight variations that will no doubt appear on one side of the house, where I am following the exisiting roof line. The process of re-battening and so on should allow for some fine adjustments to compensate.

I shall be very meticulous in measuring things for the truss manufacturer, in particular the profile of the rafters to ensure the roof line doesn't vary.

How long does it typically take for the walls/trusses to be built?

[namtrak]

After you get your quotes, whichever truss manufacturer you decide upon should come out and measure up onsite. I asked each of the places where I got quotes if they would come out and measure up, and one that said they dont do site visits didnt get the business. The one I ended up running with came out twice to measure up.

My only advice is that they take multiple measurements to cross check squareness etc. The pitch length on our house was different and wasnt taken into account, and the existing wall height was also different in a couple of places - needed some adjustments when the trusses went on.

The trusses had a 3 week lead in, so I ordered them 4 weeks before I needed them. Time will depend on how much work the trusser has, for every quote I got I asked how much lead time there was for a job.

Cheers

[silentC]

If you want to do it right make your frames yourself to factor in all the errors that have accumulated over the last however many years.

OK, let's look at what part a wall frame plays in the building. Apart from the obvious, it controls the ceiling height/height of the trusses and it controls the footprint of the building.

What I'm struggling to come to terms with is why people think that every part of the wall frame needs to be custom made to account for errors in the existing building? Presumably, the average extension being somewhat rectangular and under a single roof line, your new wall frames will interface with the old building in two places that count: the two external walls where the trusses will sit.

Now assuming you measure the wall heights correctly at these two points, what is the problem with making all the wall frames up to the same stud height? Would you really have different stud heights to compensate for a sag in the old roof? What is that going to do to the ceiling, window heights etc? Would you really put trusses out of line to match an existing roof line?

There are only two other changes that you might make to a wall frame to fit with an existing building: square and plumb (assuming that you don't need to change wall length). Why would you need to custom-build frames to deal with that?

The only time I can think that you would need to tailor stud lengths individually would be to compensate for an en-even floor - but you're not going to have that problem because you will make sure your floor timbers are in order, right?

Added to that the fact that you'll be getting the frames cheaper than you could make them, even if you have to spend 4 weekends mucking about at the interface, I really can't see the logic of this advice.

If you're really concerned about it, you could get all the walls in the new part made up but leave a section out on either side and build these on site to suit.

[zacnelson]

I agree with you completely SilentC.

Also Namtrak, it's good to know they are willing to come and cross-check measurements, that's re-assuring.

[autogenous]

There are only two other changes that you might make to a wall frame to fit with an existing building: square and plumb (assuming that you don't need to change wall length). Why would you need to custom-build frames to deal with that?

Yeah thats right. It is those points. The is other things like window placement if frames have to shortened or lengthened relative to walls off shooting of other walls which may have particular length to accommodate a benchtops, cabinets, etc

If the back wall is out of plumb then there will be gaps top to bottom but you can fix that though it is a bit of messing around.

If one side the house is out of parallel with the other side then when you try to line up the existing you will have a kink if the side walls of the new are to be lined up with old side walls. When you build it you will see it even though the back wall measured it may not be the same for the new back wall if the side walls are out.

If the house is square, level and plumb you should be fine.

My point is most chippies would want to build the frames to suit the "old" house on site

[rileyp]

About your love of colourbond.

The thing I dont like about it for the roof is how ordinary the white bird poo looks under the antenna
I think colourbond is excellent for everything other than the roof which should in Australia be zinc..
Its also the most reflective which makes it the coolest in summer and you cant really see the bird ???? either oh and its cheaper!

The things that sets one metal roof apart from another is the use of a scallop cutter on the ridge and hip capping's.

I personally don't like it but roofs that have this done look special and it takes a while to pick it but when you you do you go ohhh!
I think most hire places have them available.
cheers Rileyp
http://www.steelselect.com/image_man...7ff7d8fde3.jpg

[zacnelson]

Yes, it's interesting in books I read about roofing they always refer to cutting the ridge and hip capping like that, and yet I NEVER seem to observe it when I drive around admiring other peoples' roofs! (Like the guy in the colorbond ad)