# Forum Home Renovation Sub Flooring  Attaching timber to concrete stumps

## appublic

About a year ago I wanted to attach some bits of treated pine to existing concrete stumps (200x200). This was just to provide something to attach battens to, as you can see the pics. Initially, I thought I'd fasten into the stumps using concrete screws, but after reading some of the posts below, decided to go with glue instead. 
 - http://www.renovateforum.com/f198/dr...umps-ok-25946/
  - http://www.renovateforum.com/f198/fi...e-stumps-8430/
  - http://www.renovateforum.com/f198/fi...-stumps-72815/ 
 I chose SikaBond. I did about 25 of these about the place. After about 4 months, one of them came apart. 12 months later, every single one has come apart. I had even experimented with gluing two timber pieces to each other. Yesterday that 1 yr old experiment came apart in my hands with the slightest bit of pressure (see last pic). 
 So I'm obviously doing something wrong, and I hope someone can point out what. I'm still inclined to steer clear of drilling into the stumps - simply because a bunch of people apparently more qualified than me suggest it's a bad thing to do (and though there are people who counter that, I'm not about to use my house to find out for sure). 
 - this is an old Queenslander that was restumped about 3 years ago
  - concrete stumps are 200x200
  - most do not have well placed holes to put bolts through (I've used them where that's possible)
  - the stumps and battens will be painted
  - the stumps/battens are quite visible in the patio area, so a clamping solution would have to look alright (see middle pic)
- the areas to be battened vary from very small (in the middle pic) to larger angled shapes, but nothing huge. I've made them already, they've just fallen off where the glue has failed 
 Any help would be greatly appreciated. I hate doing a job twice, and I REALLY want to avoid doing it three times!    
 Thanks,
 Andy.

----------


## DuckCommander

Yeah you need a mechanical fixing.
Drill and epoxy gal threaded bar into/through your stumps, min 100mm edge distance, min 100mm fixing spacing. Edge distance should ensure you miss vertical reo and drill a pilot hole to ensure you miss the ties. Patch any unfilled holes with low shrink grout.
Done correctly it will not be detrimental to your stumps. 
Curious to reasoning against it though....

----------


## phild01

I've no experience or knowledge about concrete stumps but wondering if they are pre-stressed.  I might be hesitant to drill as well.  But maybe you could frame batten around each one, and then secure an upright piece to these to hold the lattice.  So 4 short pieces 70x35 (2 the same depth of the stump) screwed as a clamping type frame, one at the top and one near the base.  Then screw another 70x35 upright between the two frames.  Screw your lattice to these.

----------


## Pulse

you don't need a strong fixing, just use a 5mm bit and hammer in mushroom fixings with gal angle, the fix the gal angle to the timber. Construction adhesive was never really going to cut it, especially with the release agent they probably used to cast the concrete, and strong non-porous stumps. Polyurethane adhesive like sikaflex may have faired a bit better.  
Cheers
Pulse

----------


## intertd6

You need some sort of mechanical fixing as mentioned above, there is a simple nail type which has a bent shaft & is driven into the timber & concrete, commonly used for formwork in tilt up slabs, I can't remember the name of them. When the guys run out of them they will just drive 75 x 3.75 bullet head nails into the drill holes stuffed with some tie wire, for your situation gal roofing nails & gal wire would be ok.
regards inter

----------


## phild01

Spaghetti!

----------

