Thread: attach frames to slab

I would use dyna bolts
les

From my understanding of the framing code (and I regularly have trouble understanding it), it depends on what type of bracing, if any, the wall has.

The minimum seems to be one 75mm masonary nail at not more than 1200mm centers for no or type A bracing.

M10 bolt or other 13 kN capacity connection at each end intermediately at max.1200 mm centers for type B bracing.

The plans should specify the type of bracing for each wall.

It seems to me that you couldn't go wrong with 10 mm dynabolts at 1200mm centres on all external walls and any internally braced walls and 75 mm masonary nails at 1200 mm centers on internal partition walls.

This may be overkill but knowing what I know now I would be at 1800 centres I would be fixing chemical anchors through the bottom plate attaching a length of threaded rod to it with a threaded rod joiner to go up through the top plate with a large washer and a nut on the threaded rod on top of the top plate.

Not that anyone pays any attention but a dynabolt only 45mm from the edge a concrete slab is not sufficient. It needs to be a chemical anchor to avoid shear cone failure. But everyone uses dynabolts and gets away with it.

NSW Framing manual says tie down at max. 3000mm centres for trusses spanning 1200mm and 1800mm centres for spans greater than 1200mm but less than 16000mm.

The actual tie-down depends on the required design strength, which is a factor of the wind rating in your area and the type of construction.

For slab, it pretty much requires bent bolts embedded in the slab. However it's only an extract, so there could be other details in the standards or the building code that it doesn't cover.

As it's too late for that, I'd go along with the chemical anchors. We used both at our place. Embedded bolts mostly but chemset anchors wherever the bolts were in the way or we thought we needed more tie down in a particular spot where we hadn't put a bolt.

Bazza's suggestion is worth considering.

Is there no tie-down detail in your engineering drawings?

Forget dynabolts use the concrete screw bolts as they can be used closer to the slab edge than a dyna without cracking/spalling and if you ever need to, they can be removed easily and even reused unlike a dynabolt.

Nominal fixings of bottom plate to slab (i.e. nails) are ok however you must have dyna/screw bolts at each end of any braced wall section.

See if you can get/borrow a copy of AS1684.2 - non-cyclonic (Residential timber framing manual) it isn't that hard to follow and will give you all the info you need. The fixings are dependant on what wind clasification/region you are in.

Another thing to think about if using chem-set is that you have to be very sure that the holes are cleaned out, this is very important otherwise you won't get the full bond required.

> Forget dynabolts use the concrete screw bolts

Nah!!!!!!!!!

Forget both!

Go Chemical Anchors,
they're for me.

ramset the frames in place then get young bloke or wife to go around putting screw bolts in.

screw bolts kill chmeical anchors in this application i do like chemical anchors but not for this job.

screw bolts kill chmeical anchors in this application

How so?

1. you can drill hole and 100% tighten screw bolt in one go, chemical anchor you have to come back after it has gone off and tighten.

2, for 100x10mm screw bolts box of 100 around 60 dollars, to use chemset you have to buy large gun (little size containers run out to quick) buy the chemset and extra nozzlez plus the buy anchor of some type or cut threaded rod up and using nuts and washers.

3. you dont need to clean / blow out concrete dust from hole

4. it sees to be quicker using screw bolts plus you cn tigthen them up with cordess fitted with socket and adaptor

both methods work fine and are a massive improvmnet on dyna bolts

Fair enough, just curious, I thought you might have been suggesting that the screw bolts were stronger. Yeah probably quicker but you have to get the hole size right. Hadn't seen those screw bolts before when we built our place. One of the guys came home with some and we used them here and there but wasn't sure about them.

i dont know the numbers but both chemset and screw bolts and stronger than dyna bolts.

you also use frame anchors (big plastic plug with large screw) these are also stronger than dyna bolts and easyer to use.

i just like screw bolts.

Originally Posted by Gaza

i dont know the numbers but both chemset and screw bolts and stronger than dyna bolts.

you also use frame anchors (big plastic plug with large screw) these are also stronger than dyna bolts and easyer to use.

i just like screw bolts.

From an old Ramset Rep

A Dynabolt and a Screwanka at the same diameter and the same embedment depth the Dynabolt is slightly stronger in tensile strength to the Screwanka.

A 10mm chemical anchor at a 90mm embedment depth has twice the tensile strength of both of the above.

builders use concrete nails or dynabolts (1200cts) as this is the most effecient method of fixing the bottom plate, and nothing wrong with it either i am yet to see the walls of a house ripped off a slab.. if you think its worth the extra money and time to chemset the plates down even better