building code/construction question

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12 years 6 months ago #21370 by Andrea
building code/construction question was created by Andrea
Having removed the gib from a wall of one bedroom so we can insulate from the inside, we're quite puzzled by the fact that the wall studs are not placed at regular intervals. They are anywhere from 16-24" apart. What does the building code stipulate?

Also, in the US, when you put up insulation (wall batts), you also put up a vapour barrier on the inside, over which the bib is installed. Asking about it at the home centre just got some raised eyebrows. Not standard here, I presume?

We have deduced (from the labelling on the back of the wallboard we took down in the bathroom) that the part of the house that we're working on now was added on in the 1960s, and the original part of the house was built in 1905-1910 (haven't started on that part yet... more surprises await, I'm sure!).

Andrea
Oxford

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12 years 6 months ago #310398 by wino
I think the building code now stipulates the outcome rather than how a wall may be built - in that it would have to be capable of bearing X amounts of stress. So the gap necessary between studs is a matter of the size of the timber etc, the type of gib used and any other bracing also plays a part.

Of course something built in the 60s may or may not have been done with the benefit of a building permit - is it on the property file in the council?

You should be putting in building paper and insulation before putting the gib back up. (the building paper should go on the outside of the studs)

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12 years 6 months ago #310399 by GrantK

wino;294946 wrote: You should be putting in building paper ... before putting the gib back up. (the building paper should go on the outside of the studs)

Could be very difficult if not impossible to do with the outside cladding in place don't you think?

Definitely put the insulation in though. I have never seen any such thing as a "vapour barrier" inside the walls of NZ houses. Is it to protect against vapour being emitted by the insulation? Or from some other source?

Definitely a strange idea...

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12 years 6 months ago #310406 by wino

GrantK;294947 wrote: Could be very difficult if not impossible to do with the outside cladding in place don't you think?


That was my thoughts - yes it should have some but might be a bit difficult to install in the right place so maybe flag it....

On the other hand we have a 100 year old house too and in many places it shows a lot less deterioration than a 20-30 year old house. So who needs building paper. Though that may be more related to the timber used - our villa is heart kauri framing and your 60s addition is probably something else.

Edited with a further thought - was the addition built in the 60s or was that when they gibbed it - most villas didn't get a reline from their orginal scrim until about that time as it wasn't until round then that people got concerned about the fire hazards of scrim, and gib wasn't readily available until around then.

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12 years 6 months ago #310408 by Andrea1
Thanks for the replies. I'm guessing the wood in the walls is macrocarpa. It's a light-coloured wood, rough cut, no knots, but there are bits and pieces of rimu (reddish wood) as well.

I'm trying to remember where we were living when vapour barriers were just about required in construction... I think it has to have been Oregon or Washington, which get more extreme weather conditions compared to California where I grew up... I'm pretty sure they're still required in Northern climes (based on what I've been reading on the internet), but it also sounds like there's some controversy now as to whether they do more harm than good. It's meant to keep condensation in a room from penetrating to the insulation in the wall cavity.

DH has found some references to dwang spacing as well... but there aren't any in this wall (which is an exterior wall)... it's a short wall, about 4.6m, so maybe it wasn't thought necessary?

There are no plans, not much of anything really, lodged with the council.

Andrea
Oxford

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12 years 6 months ago #310413 by Andrea1
Another question which has just come up while DH is reading about vapour barriers... just what exactly defines a 'leaky home' in New Zealand?

Cheers
Andrea

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12 years 6 months ago #310422 by wino
Dwangs were never put in these older houses as they were lined with timber on the inside which gave them sufficient bracing not to need it.

The leaky home thing is a later issue - old houses were intended to leak to a certain extent but there was room for the damp to leave again so not an issue, also the framing was either treated or of a timber that could handle a bit of damp every now and then. The leaky homes that are the issue now were designed to be fairly airtight and not to let water in past the building paper (on the outside of the studs). They were then framed with untreated pine which doesn't like getting wet and quickly starts deteriorating (and growing toxic moulds) so when the damp barrier (cladding and building paper) fails there is a problem.

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12 years 6 months ago #310427 by powerguy
As your house is an older one it would only have had to comply with the regulations at the time it was built. Modifications can mean that you are required to bring parts of it up to the modern regulation so be careful what you undertake. A simple reline will probably be ok.

The logic on moisture barriers is a bit confusing. The cladding supposedly keeps the outside moisture (rain) out. The majority of moisture in the wall will come from the inside (cooking, bathrooms, breathing). Many other countries decide to put the barrier on the inside so this moisture does not enter the wall cavity and is vented by air circulation. Here, possibly because of the mostly temperate climate, it was decided to put it on the outside and have that moisture pass through the wall cavity. Not too bad in the older days when walls had ventilation and breathed easily.

Nowadays with tight cladding and no vent holes in the top and bottom plates it can become trapped between the barrier and the cladding. That, combined with the cladding not always being moisture proof (Why did they bother putting it on - just to look good?) has in part led to the leaky homes. Now these claddings are required to be spaced off from the wall frame with a batten to allow air movement.

If you have no building paper in the wall, I would suggest cutting squares or strips to insert into the spaces before fitting insulation to allow the moisture to be taken away from the insulation. If your home is clad in weather board, hardiplank or such it will also improve the insulation performance by limiting the air movement coming through the cladding and not allow it to blow through the insulation.

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12 years 6 months ago #310432 by GrantK

Andrea;294956 wrote: Thanks for the replies. I'm guessing the wood in the walls is macrocarpa. It's a light-coloured wood, rough cut, no knots, but there are bits and pieces of rimu (reddish wood) as well.

It sounds like Kauri Andrea. The way you have described it is exactly what it looks like. If you make a cut into it, put your nose up close and smell carefully. It is almost a sweet smell, quite unlike the pungent smell of many other timbers.

Macrocarpa is very prone to splitting so I have not seen it used in wall framing at all. It also has a rich golden colour, usually with frequent knots. Not really a good building timber at all, but very nice for furniture and mantelpieces when cut into thick slabs. The inevitable cracks are usually filled with resin.

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12 years 6 months ago #310444 by Hawkspur
A quick run-down on Vapour barriers, leaky buildings and New Zealand construction:

Vapour barriers are not used in New Zealand construction except in specialised situations such as swimmig pools where moisture levels are very high and in mountainous areas where extremely cold weather occurs. Our climate does not generally require a vapour barrier.

If one is used it is absolutely critical that any vapour barrier is installed correctly, because they do completely stop the movement of moisture, and can lead to severe dampness problems where they are installed on the cooler side of insulation, as mositure moving into the insulation cools as it travels through it (the insulation is warm on one side and cool on the other) and if the dew point or temperaure at which the vapour forms into water is in the insulation, it settles there.

New Zealand construction commonly uses breathable membranes generally known as building wraps. These allow vapour through but do not allow liquid water to pass. The cladding acts as the main rainscreen stopping the bulk of water, but the wrap is the barrier to all drops of water.

This method of construction was not the cause of leaky buildings, but the design and workmanship was. People were often relying on paint (over plaster) to stop the bulk of water, and fine cracks and no flashings meant this failed. This combined with a change to kiln dried untreated pinus radiata (without the inherent rot resistance of other timbers previously used), and poor ventilation of interior moisture sources, and a reduction in the training of builders regarding the role of flashings, meant the high levels of damp quickly led to rot.

Now cladding systems such as these require a drained cavity outside the building wrap to reduce the amount of water that might reach that far, and flashings are required.

Stud spacings are at a minimum distance depending on earthquake and windload and wall height etc. Where they vary, it could be to suit placings of elements such as doors etc or just be laziness of the builder. If they are regularly spaced it saves materials.
Dwangs or nogs are often only required where items are to be attached to the wall. eg towel rails, cupboards.

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12 years 6 months ago #310480 by Azza
Your house will most likely have irregular floor joists as well...don't worry about it, that's just how things were done back then. The older houses are in better shape than the new houses. (I'm in the building industry and every time I have bought I went for pre 1980)

Just pull the Gib off and use High Density Polystyrene instead of Batts.
Batts will slump in the wall over time leaving cold patches and also slump against the cladding if you have no building wrap and strapping and can cause leaky issues further down the track. Poly will continue to stand upright in 100 years and will allow air movement between itself and the cladding and will not absorb water/moisture.

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12 years 6 months ago #310506 by LongRidge
Unlikely to be kauri but possibly one of the beeches.

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12 years 6 months ago #310509 by Simkin

GrantK;294985 wrote:
Macrocarpa is very prone to splitting so I have not seen it used in wall framing at all. It also has a rich golden colour, usually with frequent knots. Not really a good building timber at all, but very nice for furniture and mantelpieces when cut into thick slabs. The inevitable cracks are usually filled with resin.

Our house has macrocarpa framing, no splitting. Today it is considered one of the best timbers for building houses - but not if it is from a macrocarpa shelterbelt. It does not need to be treated and is a lot stronger than pine. Rimu, kauri and totara are too expensive for most people today so macrocarpa has become quite sought after for this purpose.

Oregon is the one prone to splitting - did you mean that?

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12 years 6 months ago #310510 by Simkin
Sorry, Andrea, not much good for you what I wrote above.

However, if you only put in insulation from the inside without building paper - over time the insulation will fall towards the cladding, leaving huge gaps for cold air to circulate.

You could at least try to get strips of building paper and carefully pull them through the gap between the cladding and the studs, starting from the bottom. I'm not sure about how to fasten them to the timber but there are thumb tacks? that could be used. This would keep the insulation in place.

Also pink batts don't keep their shape as well as wool insulation. We did some renovation and the old pink batts (20 years old in the extension) had sagged a lot.

Our walls are very irregular, too, and we had to cut the insulation to fit.

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12 years 6 months ago #310536 by GrantK

Simkin;295070 wrote: Our house has macrocarpa framing, no splitting. Today it is considered one of the best timbers for building houses - but not if it is from a macrocarpa shelterbelt. It does not need to be treated and is a lot stronger than pine. Rimu, kauri and totara are too expensive for most people today so macrocarpa has become quite sought after for this purpose.

Oregon is the one prone to splitting - did you mean that?

Thanks Simkin; I stand corrected [:I]

Maybe some of the Macrocarpa furniture I have seen was from a shelter belt; I don't know. It certainly had a lot of splits in it.

I am also familiar with Oregon Pine. It has very closely-spaced growth rings due to the climate where it is grown, and has a faint orange colour. The Oregon Pine boxes I remember didn't have any splits, but the wood was very light in weight, and not very strong.

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