top plate anchoring

[tonee]

Hi

We are in the process of converting our free standing garage into a granny flat.

The garage is single brick construction. To meet building code we will be building internal stud walls. We are removing the current flat roof and replacing it with a truss hip roof.

My question is regarding the top plate. The company that we are ordering the trusses from won't give any details on how we can anchor the top plate to the external brick walls. I am hoping that someone could give me some information as to the best anchoring method.


Thanks
Tony

[echnidna]

Its normal practise to fix trusses to the stud walls not to the brick outer veneer

[Groggy]

I bought a book a while ago called

"The Australian House Building Manual"
by Allan Staines
4th ed
ISBN 1-875217-18-5


It is very useful to see how things are done and put together. I would not use it as an authoritative source, use builders or architects for that, but it is very useful to get an idea of how the houses are constructed. I think it was about $35 at Bunnings.

[Grahame Collins]

Groggy,
Did it have this
Strictly for education purposes

Grahame

[tonee]

HI Bob

Unfortunately the internal stud walls have to be non load bearing as they will only be sitting on the slab not footings.

I am wondering whether I need to chase threaded rods into the walls at certain points then bolt the top plate to those rods. Or is there another method using chemi anchors etc?

Thanks
TOny

[Brickie]

HI Bob

as they will only be sitting on the slab not footings.

Like all new houses on a slab?

[Groggy]

Groggy,
Did it have this
Strictly for education purposes

Grahame

Grahame, there are two variations of the diagram on the left, there was no equivalent to the diagram on the right. (that doesn't mean it isn't ok, just that it is not shown in the book)

Edit: Hang on, yes it does. Page 20 shows that method (slight variation) whereas the primary discussion area for soffits is page 16.

[Barry_White]

This is the way it should be done.

Provided that the roof trusses will be sitting on the stud wall the normal procedure is to fix the stud wall down to the concrete slab.

To do this you drill through the bottom plate and insert threaded chemical anchors into the concrete slab. You then attach a length of threaded rod with a threaded rod joiner and run it through to and through the top plate and then put a metal plate and a nut on the threaded rod to hold the whole frame down to the slab. I would be putting these every 1800mm. The trusses are then fixed to the stud frame and tied down to the studs with builders strapping.

It is only the timber frame that is structural. The brick work is only an external skin and the usual procedure is to tie it to the timber frame with brick ties. Seeing as the brick work is existing you could fix the brick ties to the brick work with Ramset Shuredrive pins and then nail or screw them to the sides of the studs. http://www.ramset.com.au/public/arti...lID=3&menuNo=4

[Barry_White]

Just as an added point the footings of the slab should be wide enough to accommodate the stud wall because any beam footing should be at least 300mm wide x 300mm deep.

If you are going to fit the top plate to the top pf the brickwork (BTW which I wouldn't) you could Dynabolt the plate to the top of the brickwork and then nail lengths of builders strapping over the plate and down the wall several feet and fix them with the Ramset Shuredrive anchors.

[tonee]

Hi Bazza

Thanks for the information. Could you explain the reason why you wouldn't anchor the top plate to the external brick wall?

Thanks
Tony

[Barry_White]

Because No. 1 it's not best practice and No. 2 unless you can actually tie it back to the slab there is no guarantee that it would prevent uplift of your roof in a high wind storm. Perhaps the other way you could tie it down would be with a "Z" shaped bracket fixed to the top plate and again with the chemical anchors into the slab just inside the brick work and a threaded rod attached to the chemical anchor with a threaded rod joiner and up to the "Z" bracket. All this could be in the cavity between the brickwork and the stud wall.

[Ivan in Oz]

Something I found out fairly early was that:

The Walls are there to hold the roof DOWN
as much as they are there to hold it up.

Tension is a lot more difficult to deal with than Compression.

[ausdesign]

If the 'pitching point' is on the brick wall then you need to remove the stud wall from the equation. It's Tie- down or uplift capabilities will not come into the calculations.
The tie-down will need to be documented by a qualified architect or designer to withstand the design wind gust speed for your particular site.

[journeyman Mick]

If the 'pitching point' is on the brick wall then you need to remove the stud wall from the equation. It's Tie- down or uplift capabilities will not come into the calculations.
The tie-down will need to be documented by a qualified architect or designer to withstand the design wind gust speed for your particular site.

In which case I'd be looking at putting a double top plate on top of the brick work with chemical anchors and tieing it to the stud wall.

Mick

[DvdHntr]

First step is to check that the existing footings will be sufficient for the extra load of the roof.
If so, then I would suggest some kind of angle steel bracket fixed to the truss and the wall (anchored) or the top plate to the brickwork and triple grips/cyclone ties.
The internal wall can be fixed to the truss with an internal wall bracket or a Pryda Hitch. It allows vertical movement so the walls will not be loaded but will be laterally supported.
Make sure the internal walls are 20mm under the bottom of the trusses.
The building will most probably not need additional wall bracing but if you install it in the walls make sure you use shear blocks.

Your other option is to pour an over footing and load the timber walls on top but I think that is probably more expensive and messy.