Drilling screws into lime floor slab help!

[Snowbeetle]

Hi there, 


We laid our lime floor slab just over a year ago. It is 100mm thick. We have been repairing walls and fitting roof windows and now come to partition up our internal space into the rooms we need.

 

We are doing stud walls and need to screw our floor plates onto the floor slab. 

We expected the lime slab to be more friable when screwed into than concrete so expected to need rawl plugs for the screws. However as we drill into the slab the drill bit is tearing a wider hole than we need and we aren't sure how to resolve it. We need to find a way to avoid that or take a different approach to the partitions altogether. 

The drill rips the aggregate out of the slab so makes a wider hole than you are drilling for - you don't get a clean hole like you would with concrete. We have tried using a narrower drill bit but the width is still uncontrollable, partly because the drill bit can move around in the hole and partly cos the aggregate is torn out. Also the drilled material is not exiting the hole properly so the depth is spoiled by it falling into the hole also. 

 

Bit of a head scratcher at the moment... any sage words from the wise?

 

[Danny68]

Are you using sds/ hammer drill ? If you are  I suggest you get a diamond tip bit  in a normal chuck ( no hammer ) , it pays to buy a better quality  one .

 

 

[Stewpot]

That's the sort of situation (irregular, unpredictable holes) I'd use chemical anchors for:

 

https://www.youtube.com/watch?v=oUJPjJsdl0c

https://www.toolstation.com/screws-fixings/chemical-fixings/c102

 

To be sure, I don't know if it is compatible with lime, but I think it's pretty inert when set. It certainly provides a very strong fixing in concrete and masonry.

[Onoff]

Could you just bond the floor plates down?

 

Maybe with some added screws just poking through the bottom of the floor plate (try and miss any UFH ?), like football boot studs almost, to give some shear resistance. 

Edited January 28, 2020 by Onoff

[nod]

As above Seal for dust and simply bond the sole plates down 

I normally use Sika-Flex 

Bond them down a leave overnight 

[Russell griffiths]

+1 to stick them down. 

[scottishjohn]

22 minutes ago, nod said:

As above Seal for dust and simply bond the sole plates down 

I normally use Sika-Flex 

Bond them down a leave overnight 

you will need to be seal the surface VERY well.more than  one coat  if its at all pourous -

-cos the sixa flex will only have permanent bond to that sealing layer 

sixaflex will come away from dusty surface over time 

I have had sika come away from  bare concrete over a long period 

so maybe a coat of cheap garage floor paint that will bond to lime floor first .

I think i would want some mechanical fixing as well

if only  where there are door frames or ends of walls 

[Temp]

Instead of screws into plugs would through bolts be an option?...

 

https://www.screwfix.com/p/fischer-fxa-throughbolts-m12-x-116mm-20-pack/48990?tc=OA3&ds_kid=92700049190944768&gclsrc=aw.ds&ds_rl=1241687&ds_rl=1245250&ds_rl=1249413&gclid=Cj0KCQiAsbrxBRDpARIsAAnnz_MDNXkrcSF3wERpJx-6usMCqiRCOACU9yAY5Rt2kUgk4hJJGtW95NgaAvn3EALw_wcB

 

 

[Onoff]

You can get Sika CD Anti Lime Coating. My understanding that it is to simply seal a surface to stop it leaching lime. Whether Sikaflex would stick to that?

 

If in doubt SBR would be my goto for sealing...

[ProDave]

If the stuff is fairly soft have you tried just ordiany coach bolts or concrete screws to just cut their own thread into the floor?

[MikeGrahamT21]

How about using resin based fixings?

 

Another one to try is helical fixings, these are brilliant for aircrete, and may work for your situation too, perhaps get some samples to test, as they can be quite expensive. Thor helical is one manufacturer.

Edited January 28, 2020 by MikeGrahamT21

[Snowbeetle]

Thank Goodness for some helpful replies - phew! 

 

Really grateful for the suggestions, was going round in circles without fresh perspective and starting to wonder if we would just have to have Extreme Open Plan. ??

 

I will explore all of these suggestions and see which one stands out as best solution. 

[Stewpot]

10 hours ago, nod said:

As above Seal for dust and simply bond the sole plates down

 

10 hours ago, scottishjohn said:

you will need to be seal the surface VERY well.more than  one coat  if its at all pourous

 

9 hours ago, Onoff said:

You can get Sika CD Anti Lime Coating. My understanding that it is to simply seal a surface to stop it leaching lime. Whether Sikaflex would stick to that?

 

If in doubt SBR would be my goto for sealing...

 

WAIT! Before you consider sealing the lime floor, you have to consider why lime has been used. If the floor is insulated from moisture, and the lime was used simply because it was what was to hand, then sealing it may be OK. But if lime is used in a new build, there is usually a reason - normally lime is used because it's vapour permeable, and for it to function correctly, you have to maintain this property. No end of problems have been caused by sealing lime masonry as if it were OPC based, which means that it can no longer behave as it should.

 

If somebody else installed the floor, then I'd suggest the OP takes advice before using any sort of sealant on lime.

[Onoff]

3 minutes ago, Stewpot said:

WAIT! Before you consider sealing the lime floor, you have to consider why lime has been used. If the floor is insulated from moisture, and the lime was used simply because it was what was to hand, then sealing it may be OK. But if lime is used in a new build, there is usually a reason - normally lime is used because it's vapour permeable, and for it to function correctly, you have to maintain this property. No end of problems have been caused by sealing lime masonry as if it were OPC based, which means that it can no longer behave as it should.

 

If somebody else installed the floor, then I'd suggest the OP takes advice before using any sort of sealant on lime.

 

I assume the OP would only be doing any sealing in thin  isolated strips, where the walls he wants to stick down are?

[nod]

2 hours ago, Onoff said:

 

I assume the OP would only be doing any sealing in thin  isolated strips, where the walls he wants to stick down are?

Mark out where your duds going in pencil 

Which you would do if you where screwing the soleplate gown 

Then run round a couple of times with a 100 mil brush 

An hour later stick them down 

I do loads like this When the floors have pipework under them 

 

 

[Snowbeetle]

Thanks for the input all, it was great to check out all the suggestions cos we were properly stuck!


Stewpot's solution won! ???

So the checks revealed - Any variety of social drill bits of screws with particular threads etc doesn't get over the fact that the slab contains aggregate of variable sizes (1-10mm) which are only loosely gripped compared to concrete, so any forces carving out a hole will always rip the aggregate out before it cuts cleanly through - thus giving a hole of unpredictable width. 

 

You could seal and stick, but again as the slabs surface is only loosely bonded to itself it is a solution that would not necessarily hold indefinitely against lateral forces. 

 

Whereas the chemical anchors were fantastic - great to hear about them as hadn't come across that before. ? Is completely fills a hole of any and even variable size (unlike rawl plugs) and sets rock-hard, meaning that once in, the wall can't be pushed sideways at all. We used Fischer as they had one which was chemically compatible with the lime so there would be no adverse reaction preventing a good set. Because we are screwing a wall footplate down, the fact that if you *really* tried hard enough you might be able to rip the resin plug out of the slab is not an issue because all forces will be downward or horizontal not upward. 

Also Stewpot, thank you for the warning about seals and lime functionality. Luckily we out the lime floor in so were alert to that issue but it's still great to have a friendly warning to pitfalls of a job.