Semi-detached house (c1900) with common brick wall - earthquake risk?

[omoeroa]

I'm wondering if anyone has any information regarding what happened to semi-detached houses in the Christchurch earthquake? Ours (in Wellington) has a single storey common wall made of brick. It goes from the ground through to below the roof, so is about 5.5m tall. I'm wondering if we need to be looking at strengthening it, or removing it entirely. The rest of the house is weather board and iron.

[eri]

if the brick wall is that old i don't think it will have any steel rods tying it all together from top to bottom

so when wellington has it's next big quake it stands a fair chance of coming down and bringing the roof with it

the ? is if that will be in the next 100 years or not...

take a photo of the wall to wellington council and see what they have to say

[motivated]

Your double brick wall is a big risk in a CHCH size earthquake--It may cause collapse of your building.
Wouldnt waste your time strengthening it. You would be better to remove and replace the wall with a fireproofed timber wall. Dont even waste your time asking the council--they wont sort it for you--Get a decent designer to sort out what needs to be done--it may (or may not) need an engineers input but a decent LPB designer will be able to put you on the right track. It will need a consent
Also read recently there is a significantly greater than 50% chance of a magnitude 7 quake within 100km of Wgtn within the next 50 years

[hawkeye]

Anything with brick walls older than about 1930 is a big risk. There was a beautiful row of Edwardian 2 storey villas, semi-detached, with brick fire walls between each pair in Chester St in Chch. There were 4 pairs in a row. The middle 2 had brick firewalls on their outside walls as well as through the centre. Now the middle 2 sets of houses have been demolished and the sets of houses at each end of the row are still standing but red stickered. (They had timber/weatherboard walls on their outer walls).

The firewalls extended by about 40 cm above the roof. These came crashing down in February. I would definitely get your walls replaced. It was so sad to see the damage to these lovely homes. Also if you have old brick chimneys take them right down to the ground. Our 2 storey villa that was in flats had all of the chimneys/ chimney breasts fall into the bottom flats leaving a huge gaping hole. Then aftershocks caused major damage as the hole that was left wasn't braced (it was red stickered so we weren't allowed in) so the house basically shook apart around these holes. It may have survived if the chimneys had been taken right out and the walls braced.

[omoeroa]

thanks

Anything with brick walls older than about 1930 is a big risk. There was a beautiful row of Edwardian 2 storey villas, semi-detached, with brick fire walls between each pair in Chester St in Chch. There were 4 pairs in a row. The middle 2 had brick firewalls on their outside walls as well as through the centre. Now the middle 2 sets of houses have been demolished and the sets of houses at each end of the row are still standing but red stickered. (They had timber/weatherboard walls on their outer walls).

The firewalls extended by about 40 cm above the roof. These came crashing down in February. I would definitely get your walls replaced. It was so sad to see the damage to these lovely homes. Also if you have old brick chimneys take them right down to the ground. Our 2 storey villa that was in flats had all of the chimneys/ chimney breasts fall into the bottom flats leaving a huge gaping hole. Then aftershocks caused major damage as the hole that was left wasn't braced (it was red stickered so we weren't allowed in) so the house basically shook apart around these holes. It may have survived if the chimneys had been taken right out and the walls braced.

Thanks for the replies - it is good to get other opinions on the matter. I'll look into getting the wall either reinforced or replaced. It is so sad to see what has happened to old buildings in Chch.

[Re@der]

This semi detached situation is very common in the older parts of Wellington and Lower Hutt. These places have stood for 80 years and yes a Christchurch earthquake would take them down. But who says there is going to be one. We are being pushed by Christchurch related hysteria. It wasn't this type of building that killed people in Christchurch.A lot of buildings are being designed to allow people to escape rather than preserve the building.You probably already have this and that is why it is not in the targets of the law makers.
While you are not forced to I would keep my money in my pocket.

[motivated]

Doug--you are right--many buildings are designed to allow people to get out--but double brick structures are NOT in this category. Double brick buildings are at high risk of serious damage or collapse in moderate earthquakes.
I suggest they are in the dont buy category unless you plan to either strengthen the building or replace the brickwork.
You dont want a death trap on your conscience.
The odds of a chch size earthquake or bigger in wellington (and many other parts of nz) in the next 20-30years are higher than many people realise.

[DazRaz]

http://christchurchcitylibraries.com/kids/nzdisasters/eqwellington1855.asp

Brick buildings in Wellington have killed people before. There is much to be learnt from history.

[Re@der]

Appears from your link that none of them were houses, let alone houses with a single adjoining brick firewall.

I think that you do your best with flats houses that you rent out and fix things as you are working in the same area of the building or system but not individually targeting things at great cost unless there is a market return. For example how many landlords have retro installed tempering valves on all Hot water systems or replaced single glazing with double glazing. Just because these things are in the current building code you wouldn't necessarily do them unless you were doing work with these items. I would have a similar view of the firewall between two adjacent houses. Meanwhile I am a shareholder in a multi storey building on the Terrace which at some stage will have a fix or demolish notice within 10 years but we are working on this immediately even before getting any sort of earthquake prone notice. Why ? because an earthquake prone notice could well make it unrentable and uninsurable in the current environment. These issues don't exist with the semidetached firewall.