Core filling hollow concrete masonry and single storey construction

[lavishhouse]

Heys Guys,

I just wanted to know if you have to by law (Building codes), core fill hollow core masonry walls, in single storey residential construction?

If so, is there any cheaper way of doing this. Some friends have mentioned that if I dont core fill I will have moisture problems. Is it possible to core fill using something other than concrete? It costs something like an extra $20 per sq m with concrete core filing.

[journeyman Mick]

In north Queensland masonary block construction is probably the most widely used domestic construction method. Generally, all corners are filled, as well as around each door or window opening and then generally at certain intervals (every 5th core? but I could be wrong) Plus the entire top course (or sometimes 2 top courses) are filled. We are in a cyclone prone area though and our structural requirements are higher than in non-cyclonic areas. I'm assuming that you've had (or are having) plans drawn up, with structural details done by an engineer. If it's on the plans it's a requirement.

The core filling does not give any water proofing protection to the wall, this is done by the paint system. This could be a layer or two of "block filler", a heavy bodied paint which often has particles in it, followed by a few coats of paint. Other times a mixture of Silasec, cement and water is brushed on with a broom, sometimes followed with blockfiller and then paint or sometimes multiple coats of the Silasec mixture and then paint. Nowadays of course, most places are rendered.

Mick

[Metung]

Mick, I"ve had a few sherries so please forgive me but I am wondering how you can fill the entire top 1 or 2 courses of a hollow block wall without doing the whole lot.? I hope the answer isn't too obvious or a might of to relinquish my forum membership (or I could just give up the sherry).

[journeyman Mick]

Send the sherry to me! (I won't drink it but I like to cook with it :wink: ) You use a "bond beam"/lintel block. This has no vertically aligned cores but a horizontal channel. ie it's "U" shaped in cross section. Where there's to be a core filled that meets up with this top bond beam a "half and half" (aka bisexual block :oo: ) is used. Half of this has the bondbeam profile and the other half has a vertical core.

Mick

[Wood Butcher]

You put a plug in the core to stop the concrete going all the way done. The core in concrete blocks is not straight through but tapered. Last time I did work like that we cut scraps of ply up to sit it the cores.

[eemgee]

If you go to Hanson they should have details of building a single leaf dwellings. Its about 10 years since building a hall in this method when Hansons were called Besser but we had to connect the reinforcement in the slab to rod which went through the wall and connected to the roofing timber to tie the whole roof down. The cores were filled with concrete where the rods were and then a bond beam as described by Mick surrounded the wall at the top through which the rod passed and which was also reinforced with 2 8mm rods.
Wayne