replacing brick piers with stumps

[rscho]

We've new to posting but have been following alot of the threads in these forums, and are hoping the collective wisdom can answer a question we have.

We've bought a 1940's double brick house in Melbourne which has had subfloor drainage problems in the past. We're in the process of replacing some joists and levelling the timber floor. The bearers are resting on brick piers but the mortar in some is crumbling and the hoop iron that secured the bearers to the piers has long since rusted away. The piers are two bricks wide and about 6 bricks high of which about 5 are under ground. Because of the limited access we can't easily re-mortar the bricks with a threaded rod to secure the bearer and help in levelling, so we're thinking of replacing them one at a time with 100x100mm precast threaded rod concrete stumps set in concrete. Are there any differences in the load bearing capacity of the bricks versus stumps if they have the same "footprint" and can anyone see any problems with replacing crumbling piers with concrete stumps? Any advice would be much appreciated.

[ozwinner]

Hi and welcome.
When you replace the bricks with a stump, you will have to concrete it into place, which will give the same earth bearing as a brick pier/pad.

So all in all, they should hold the same weight.

Al

[bsrlee]

There was I, wondering why someone would want to replace termite resistant brick piers with wooden stumps.

Structurally, about the only thing I would suggest is that you make sure that you have some sort of damp course between the concrete and the timber joists, either under the pier or on top, otherwise the moisture from the soil (and it sounds like you have plenty) will make its way up the concrete by capillary attraction & start dry rot in the timber. That is quite likely why the mortar between the bricks is crumbling.

Other than that, get a hard hat each, knee & elbow pads, a water proof lighting system, ventilator/fan & line up a good back straightener - you'll need 'Im after crawling around down there.

[rscho]

Thanks for the reply guys. That's answered our question.

Yes bsrlee, there has been alot of moisture under the house. I found that one of the fence posts was set in concrete straight through the stormwater pipe. The neighbour says the fence has been there for 20+ years so there's been alot of time for water to go nowhere. It caused quite a bit of damage and the previous owners seemed to have tried everything except fixing the stormwater. Since lifting parts of the floor over summer its dried out heaps so we've got fingers crossed that no cracks start appearing. It seems subfloor ventilation and damp course weren't much of a priority for the builders.

We're also considering forced ventilation because there's so little opportunity for natural crossflow. Has anyone got any experience with electric fans? We're considering turning them on and off using an outside humidistat but think that may be overkill.

[bsrlee]

If you have any brick fireplaces, either intact or bricked up, you may find that the ventilation was supposted to use the chimney draught - look for some 'new' brickwork under the floor around the chimney 'stack' or foundation - its amazing how many people develop a phobia about ventillation & start blocking everything up - like my elderly mother. Just chop the 'new' bricks out & you should have airflow up the chimney - unless they got real 'smart' & chopped it off in the roof & bricked it over.

If you have double brick walls, try removing the odd brick from the wall below floor level on the sides that get hot in the sun - again, use natural air movement to draw moist air up out of the sub-floor cavity. If you are worried about vermin, just make some screen blocks from mesh & some treated 1x decking timber.

[ozwinner]

If you have any brick fireplaces, either intact or bricked up, you may find that the ventilation was supposted to use the chimney draught - look for some 'new' brickwork under the floor around the chimney 'stack' or foundation .

Gees thats a new one on me??

What stops the embers from dropping under the floor and setting the house alight.

Al :confused:

[bsrlee]

Ozwinner - Much the same thing that stops the rain from coming down the chimney & flooding the place - there is a 'kick' or off set in the vent path. The ones I have seen were in fireplaces designed for a cast iron fireplace insert - like the Victorian marble fireplaces that everyone was ripping out 40 years ago & are now paying an arm & a leg for in a 'salvage' shop.

The fireplace in my current home was designed for a gas 'fire' and dose not have a sub-floor vent & only a tiny (100 x100 mm) sliding vent in a plate set into the chimney uptake. I think a lot of old fireplaces were modernised by having the sub floor vents bricked up, the cast iron bits ripped out & a 'modern' coal gas heater fitted - much cleaner than coal or coke, no need for a chimney sweep & only a few people succumbed to carbon monoxide poisoning if the gas was left on - less than caught alight from sparks popping out of the fire.

[ozwinner]

Ozwinner - Much the same thing that stops the rain from coming down the chimney & flooding the place - there is a 'kick' or off set in the vent path.

How so?
If X ammount of rain enters the top of a chimney opening then X ammount of rain must come down the flue.
If not, where does the excess go.?

Al :confused:

[echnidna]

yer teasin" Al

[ozwinner]

yer teasin" Al

Just curious Bob.

Al

[bsrlee]

Actually the amount of rain that can fit into the chimney is quite limited, the 'kick' in the chimney just stops the rain going directly into the fire, the water actually just runs down the brickwork & usually evaporates before things get serious - in one of the fireplaces with sub-floor vents the water would go down them as easily as going out onto the floor, but it would have to be pretty monsoonal rain to reach that state.

Ditto the directly air-delivered Dynamic Lifter - however if the whole parrot goes down the chimney it is quite a job to get them out & the little b******s can bite & aren't the least bit thankfull either.