Hoop Iron Specified in Double Brick Base Walls

[zacnelson]

Hello, I just got my plans back for my new extension at the back of my house. It is not a very adventurous or large addition, and I will have the luxury of being able to tackle it gradually whilst living comfortably in the existing house.

The extension will continue the style of the home, which is brick veneer with timber floor. The plans specify double-brick base walls, with a 4x2 timber plate attached to the inner leaf to which high-span floor joists will be nailed. Apparently the 4 x 2 on top of the base bricks is to be attached with hoop iron, which (I think) is mortared in close to the footings, and brought up between the two layers of brick. (I may be wrong on that).

I would love some clarification on this; I totally understand every other requirement of my plans but this one important element is the only thing that is foreign to me. The existing house doesn't have double brick walls, it has piers around the perimeter, bearers and joists, and concrete stumps throughout. This new design is obviously a little different, there are no stumps and no bearers.

If anybody has detailed drawings or photos that would help me out, I would be really appreciative.

Regards,

Zac

[journeyman Mick]

............If anybody has detailed drawings or photos that would help me out, I would be really appreciative..........

Go back to whoever prepared your drawings and request a detail, it should be included.

Mick

[zacnelson]

There was a detail of the brick base walls, however it was not very `detailed'!! It had an arrow pointing to the top plate and a comment saying `90x45 MGP10 top plate fixed to brickwork with hoop iron straps @ 900 ctrs' but that just raises a lot of questions in my mind. Obviously I understand the 900 ctrs bit, but my queries are about the mechanics of how to do it all, as specified in my first post, and being a visual person I would love to see a picture of it in operation.

[ausdesign]

I assume that the base - double brick - is more than 1200 high ?

[zacnelson]

No, there is only about 150 - 200mm between normal ground level and the floor joists (but the base brick walls extend down a few courses below NGL to the top of the footings)

The original house is a very average 1960s triple-fronted cream brick in Altona, where there are no hills and all the houses are pretty low to the ground.

[Brickie]

Hi Zac, I cant for the life of me think why they have drawn it up as two skins of brickwork?
Most of the footings Ive worked on are single skin with piers.

The hoop iron gets built into the outside skin as low as you can get it and the pier, well usually, gets built behind it.

[myla]

The extension will continue the style of the home, which is brick veneer with timber floor. The plans specify double-brick base walls, with a 4x2 timber plate attached to the inner leaf to which high-span floor joists will be nailed. Apparently the 4 x 2 on top of the base bricks is to be attached with hoop iron, which (I think) is mortared in close to the footings, and brought up between the two layers of brick. (I may be wrong on that)

hello,

you have pretty much summed it up already,

the hoop iron is laid in the mortar bed a low as you can get it every 900mm centre's, and fixed onto the 4 x 2,

lay the skins reasonably tight

thankyou

myla

[zacnelson]

Thanks for all your responses guys. Brickie, I think the reason it is double skin rather than piers is because there are going to be no bearers, hence the high-span joists will be at 450 centres, which would mean the piers would be basically everywhere anyway.

Sorry to be asking so much, but what I don't really get is how the hoop iron would really hold down the 4 x 2 - surely it would need to be strapped over the 4 x 2 and then attached somewhere else? Is it okay for the hoop iron to just be nailed to one side of the 4 x 2, and to rely on the weight of the joists to hold everything in place? I have attached a quick drawing I just did in microsoft word to show 2 options.

[ausdesign]

i surmise that because of the low clearance the designer has nominated a double skin to give continuous support to the plate [rather than having a standard bearer size on piers that would be nearly in the dirt]
In a 'normal' brick veneer construction there is no tie down requirement to the perim. foundation so I would say that possibly the hoop iron notation is a 'bonus' and not strictly required as a tie down.
In an N1 or N2, site such as the Altona area probably would be, it used to be with garages that the perim. beam or pitching plate for the roof was nominated to be tied down at 900 centres with hoop iron 1200 down into the brickwork.
In your situation I would say the hoop iron is nominated just to steady the pitching plate, as the 3 or 4 courses won't do much.
In any case it will be put in by the brickie, bent under & bedded in with the first course, & brought up the cavity.

[ausdesign]

Normally up & over with nails in top & on the joist side face of the plate.

[zacnelson]

Ah, excellent, it's all becoming clear now. Thanks again!