Church floor sagging - advice?

[Alex Rogers]

Hi - new member here. We live in an old church in Sydney, mostly open plan, and the main floor (7m x 14m timber floor) has always had a bit of a sag to it. A couple of the piers are subsiding gently - they have probably sunk 10mm in the last 5 years, but it is now very noticeable and starting to cause some issues (cracking of kitchen splashback, etc). At least we always know where to find any of the kids balls...

We should probably get a structural engineer to survey, and then repair / replace the piers - but looking through the forum I see some members have recommended simply jacking up the joists and then packing them with some non-compressible materials. This sounds a lot cheaper and potentially a viable fix, even if it does have to be done every 5 years or so. Any thoughts / advice on this?

Thanks

[Black Cat]

Best to find out why the floor is sagging. If you have subsidence in one spot, it will eventually start impacting on the walls and other structural bits. So better to identify the problem and sort that out before jerrying up solutions to the symptoms.

Can you get under the building and take some photos of a) the offending piers and b) the bearers, and c) the outer footings?

Is there a drainage problem anywhere? (i.e. soggy areas of soil where moisture sticks around longer than usual?)

Are you on a slope?

Who did the original reno? where they tradies or DIYers?

Quick fix solutions are rarely a long-term solution. Better to do it once and well.

[Ken-67]

If the sag is getting worse, you have stumps that are still sinking. You need a proper investigation to find out why, before you start trying to make repairs.

[Alex Rogers]

Thanks for the replies.

"My original building inspection report noted : The subsidence noted above is most likely due to the shallow depth footings on semi-reactive clay foundations. The subsidence may continue or cease subject to the prevailing weather conditions, however it should be monitored in the future for increasing movement. If this occurs, a further inspection is recommended by a structural engineer."

It has been 7 years since that inspection, and the subsidence HAS continued - but perhaps 10mm in the last 5 years - so its pretty slow. Also, it only seems to be affecting the piers under the centre of the floor, as the walls are all sound.

I spoke to a structural engineer today, who said he'd be happy to come around and inspect it, and charge me $400 for the trouble - but given the walls are not affected, he said he'd be advising me to just jack/chock up the floor anyway. So I think that answers my question :-) I was pleasantly surprised to find a consultant talking himself out of a job...

Right, off to see if this is DIY-able

[Black Cat]

My only problem with that advice is that if it is only the internal piers that are subsiding, then the reactive soil is unlikely to be the cause - that would impact on the outer piers were the soil was subject to repeated wetting and drying incidents. The central ones are in a stable environment so unless you have the odd river running under the house then it is unlikely to be the reactive soil that is your problem. Still, it's your house, so go with the advice if you are happy with it.

[denaria]

I assume the intention is adding to the top of the piers, perhaps while you're at it add a broader base to them too to spread the weight.

[goldie1]

It was common for brick piers to be just built on the ground. Some only 2 bricks square so they just sink into the ground over

time. How far apart are the central piers? You may have to rebuild them on a concrete footing and even add extra piers.