# Forum Home Renovation Sub Flooring  Stump Size

## adbert

Hi all,
Newbie here. I'm planning to re-stump my house (DIY). I've been following this forum with great interests.
After doing lots of research, I've decided to go for adjustable galvanised/steel stumps. I'll buy seconds
galvanised/steel tubes and weld them together with a screw top so they can be adjustable. 
My sub-floor height is around 40cm - 80cm, single storey, brick veneer house. I've estimated there are
around 50 stumps for the entire house. I'm considering the below tube sizes: 
1) 50x50x3mm
2) 40x40x4mm
3) 65x65x2mm 
With your knowledge/experience: 
1) which tube size above is the strongest?
2) as DIY, how many stumps should I jack/replace at a time? 
Thanks in advance.

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## stevoh741

personally I wouldn't use any less than 89x89x4

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## adbert

Tek Stump (Tek Stump by Stump Systems &ndash; Prices: Manufacturers of Concrete and Steel House Stumps, concrete products, sole plates and ant caps for restumping, reblocking and new house sites, Lilydale, Mt Evelyn, Melbourne, Victoria) the company manufactures stumps uses 75x75x2mm steel for their stumps up to 3 metres length. Over 3 metres, it uses 75x75x2.5mm steel. With 75x75x2mm, its cross section (steel) area is less than 40x40x4mm. Correct me if I'm wrong, the wall thickness is the strength factor not the tube size. Obviously, given the same wall thickness the bigger the tube size will be stronger.

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## BRADFORD

Out of your list I'd use 50x50x3, however I think 75x75x3 would be better.
How are proposing to make the screw top and what size thread will you be using?
Many years ago I restumped my house, used 3inch water pipe, wall thickness of maybe 4mm.
Didn't make them adjustable, just jacked each side of the old stump to the required level, removed the old stump, bolted the new one under the bearer with the bottom end hanging in a hole that I filled with concrete.
I only did one a week, so it took me a while.

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## adbert

As for tube size, I think anything bigger than 50mm looks more decent (anything less looks too tiny). However, for the given $$$ I'm trying to get the strongest of all. I'm looking at all big available bolts/nuts. For M20+ bolts, they're not full length threaded (and expensive). I'm thinking of getting (big) threaded rods, cut them up to desire length and weld them to the flat bar which will be attached to the beam/bearer (as the attached photo above). These threaded rods are hot dipped galvanised and cheap as dirt (sold on ebay). Problem is finding matching nuts for them. I'm planning to do 4 stumps a weekend with four 12T jacks. Allow enough time for the concrete to set. No rush here, so I'll take my time. 
You said you jacked each side of the stump up, so you used 2 jacks for each stump (one on each side)? That's what I initially planned to do too. But if I'm going to do that then it would take me forever (the time will be doubled).

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## BRADFORD

I agree about the tube size.
Yes I used 2 jacks per stump, you may find you need to do this because using 1 jack, it has to be pretty close to the hole with the possibility of things going horribly wrong, this would depend on your site conditions.
You will need to put a plate on the bottom of your stumps to key it into the concrete.
I'll be interested how you get along with the bolts/threaded rod, the large nuts are expensive.

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## adbert

Like I said, initially I planned to use 2 jacks for each stump for safety reasons (like you did) but since I  plan to buy 4 jacks only, it will double up the time to do all stumps.
What I'm going to do now is use one jack for each stump, the other side of the stump I'll use scaffold (as I replaced the stumps, I'll cut them up and use them as scaffold). For
added safety reasons, I plan to do four stumps on four different bearers. That is, NO two stumps are replaced on the same bearer at a time. 
I plan to use 100mm (long) x 65mm (wide) x 5mm (thick) plate for each end of the stump (welded). The middle plate will be 60mm (long) x 65mm (wide) x 5mm (thick)
under the nut for adjusting the stump height (head). The nut will be free spinning. Hence, once the stumps in placed, with a spanner the height of the stumps can be
adjusted WITHOUT removing the stump from its bearer. 
According to my calculation, if DIY adjustable stumps, they'll cost around $2-$3 more than concrete per stump (plus all the labour/time of welding). But it's worth it,
since they're fully adjustable and you don't have to worry about them for the next 50+ years. I even plan to either oil, grease or paint the inside section of the galvanised
tubes so make them last longer against damp/rust. No doubt, I'll even paint the outside as well. Eventhough no dampness in my sub-floor. 
At this minute, finding suitable bolts & nuts is the only issue for me  :Frown:

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