using SIKA 1 for tanking, I am not paying for their mortar!!

[shabba1985]

Hi All,

I am going to use sika 1 for tanking purposes in my basement. I have looked at other products but this seems to be pretty good.

My issue is that I rang Sika 1 and they said they recommend only using their spritz (sand and cement mix) for sika 1... I mean talk about money making scheme... it's just a mix of sand and cement.

I wanted to know if anyone knows the right mix for the 3 coats of sand and cement needed (and also what kind of sand... i was thinking rendering/plastering sand... is that correct??

From my research I gather this is the correct method:

coat 1: 1:1 (rendering/plastering sand:cement) for spritz left 4-6hr throw at the wall and don't trowel it in (6mm coat).

coat 2: 1.5:1 (rendering/plastering sand to cement) render coat to be left over night.

coat 3: 2:1 (sand: cement) for the finish coat, so I suppose it would be a plastering sand as you can just paint over that.

If someone please could let me know if the above ratios of sand:cement is correct and also exactly what kind of sand is used at each stage that would be fantastic.!!!!

Oh yes you should use 10:1 (water: sika1) when mixing.

cheers

shabba

 

[Micilin]

Fine sharp sand. 3mm down. Washed, salt free . (eg 'Leighton Buzzard')For all coats.

Sieve it in together with the cement to make sure you have a good mix with right grain size. Obviously not leaving any over night .

After coat 2 you need another spritz (scud) coat for a key, to be applied as soon as coat 2 is firm enough to take it . This is not as heavy as coat 1 , just 3mm approx for a key . It does not have to cover the entire surface as it is for a key, not a sealing coat like coat 1 ( say 80% surface). NO SCRATCHING for keys while tanking at any stage.

Final coat ( coat 4 as we count key coat just mentioned as coat 3 ) can be rubbed up and sponged. This can be 2.5 /1 . I would not skim it if possible.

You'll find it seems to hang for a while and you think it's never going to set, then the green suction of the coats underneath pull it in.


Tanking is not meant to be straightened in the same way as render or damproofing , as

a -ruling it off may leave the coat thin in places
b- heavy /thick areas may crack
c- the mix is expensive for filling out !

however, you can give another coat if you need to , as long as it is weaker and is keyed in the same way.

Where is it being applied and how wet is it?

You are familiar with-

lapping the coats
the fillet in all internals
no beads on externals
lapping on to floor and then screeding over
sealing any services
fixing pockets or adhesive for fittings -no drilling

 

[shabba1985]

Fine sharp sand. 3mm down. Washed, salt free . (eg 'Leighton Buzzard')For all coats.

Sieve it in together with the cement to make sure you have a good mix with right grain size. Obviously not leaving any over night .

After coat 2 you need another spritz (scud) coat for a key, to be applied as soon as coat 2 is firm enough to take it . This is not as heavy as coat 1 , just 3mm approx for a key . It does not have to cover the entire surface as it is for a key, not a sealing coat like coat 1 ( say 80% surface). NO SCRATCHING for keys while tanking at any stage.

Final coat ( coat 4 as we count key coat just mentioned as coat 3 ) can be rubbed up and sponged. This can be 2.5 /1 . I would not skim it if possible.

You'll find it seems to hang for a while and you think it's never going to set, then the green suction of the coats underneath pull it in.


Tanking is not meant to be straightened in the same way as render or damproofing , as

a -ruling it off may leave the coat thin in places
b- heavy /thick areas may crack
c- the mix is expensive for filling out !

however, you can give another coat if you need to , as long as it is weaker and is keyed in the same way.

Where is it being applied and how wet is it?

You are familiar with-

lapping the coats
the fillet in all internals
no beads on externals
lapping on to floor and then screeding over
sealing any services
fixing pockets or adhesive for fittings -no drilling

Hi

Thanks for your reply, appreciate it...


I understood everything that you said and thanks for the tips once again. Just to pickup on upon your points:

I don't know what the term lapped up means, if you could please explain further...
The fillet in all internals, i think this is when you curve the wall to the floor, I think a good technique for this would be getting a 4 inch waste pipe and curving it down.
sealing service... the pipes are behind the walls and hidden.
I think sika do a adhesive called sika 32 which is a strong adhesive... but i guess any adhesive would be good.

cheers

shabba

 

[Micilin]

Hi

Thanks for your reply, appreciate it...


I understood everything that you said and thanks for the tips once again. Just to pickup on upon your points:

I don't know what the term lapped up means, if you could please explain further...


'Lapping ' would be at any day joints where each layer is seen, so that 6" of the first coat sticks out, then 6 " of the second coat and 6" of final coat.

So that when working into it, the coats are staggered. Ie the new adjoining 2nd coat goes over the old 1st coat and so on ie no straight joint.

Also the tanking should be lapped on top the floor , staggered as above and then a watrerproof screed lapped onto that , so there is no straight joint at floor/wall junction . Not sure if I've explained that well ??


The fillet in all internals, i think this is when you curve the wall to the floor, I think a good technique for this would be getting a 4 inch waste pipe and curving it down.


ALL internals, wall to wall as well as wall to floor. 4 inch better but we always use a smaller fillet, like a small lucozade bottle . Again, the idea is to have it at juntions to bulk up stress points. IF cracking there, a fillet alone won't be good enough. A flexible material will have to be uses such as Skia supplyu , or Igas seals


sealing service... the pipes are behind the walls and hidden.

Good, as long as nothing breaking the seal

I think sika do a adhesive called sika 32 which is a strong adhesive... but i guess any adhesive would be good.

I'd be inclined to go with something water proof and flexible around any services, but for mounting onto the finished wall I suppose any thing that sticks will do!

cheers

No worries - but are you sure it needs tanking and if so are you doing the floor?

shabba

[/b]

 

[shabba1985]

Hi

Thanks for your reply, appreciate it...


I understood everything that you said and thanks for the tips once again. Just to pickup on upon your points:

I don't know what the term lapped up means, if you could please explain further...


'Lapping ' would be at any day joints where each layer is seen, so that 6" of the first coat sticks out, then 6 " of the second coat and 6" of final coat.

So that when working into it, the coats are staggered. Ie the new adjoining 2nd coat goes over the old 1st coat and so on ie no straight joint.

Also the tanking should be lapped on top the floor , staggered as above and then a watrerproof screed lapped onto that , so there is no straight joint at floor/wall junction . Not sure if I've explained that well ??

I get what you mean, i.e. its like putting up double plasterboard (for sound proofing)making sure the 2nd plasterboard is overlapped on the 1st plasterboard so no gaps are visible. Well explained.


The fillet in all internals, i think this is when you curve the wall to the floor, I think a good technique for this would be getting a 4 inch waste pipe and curving it down.


ALL internals, wall to wall as well as wall to floor. 4 inch better but we always use a smaller fillet, like a small lucozade bottle . Again, the idea is to have it at juntions to bulk up stress points. IF cracking there, a fillet alone won't be good enough. A flexible material will have to be uses such as Skia supplyu , or Igas seals

Well if you have wall to wall junctions as fillets then how would you get a good straight finished wall or is the whole point not to have one and have curved walls. How would I apply this flexible material... would i put it on the where the floor-wall meets and where the wall - wall meets? at each coat?.. or just the final coat. And also could you let me know what kind of flexible material... i know you specified skia supplyu or igas seals but i googled and nothing came up


sealing service... the pipes are behind the walls and hidden.

Good, as long as nothing breaking the seal

I think sika do a adhesive called sika 32 which is a strong adhesive... but i guess any adhesive would be good.

I'd be inclined to go with something water proof and flexible around any services, but for mounting onto the finished wall I suppose any thing that sticks will do!

cheers

No worries - but are you sure it needs tanking and if so are you doing the floor?

The walls are very wet and the previous render was flaky. I am doing the floor aswell... what mix would you recommend here? I was just going to screed it with sika 1 (2 shapre sand and 1 cement) using the fillet junction to floor and wall method (50mm). I was going to do the walls first with the first coat as the key then do the floor straight after in the 1 day... we hope.


1 Final question, would you recommend us doing the internal walls of the basement (i.e. the brick partition walls).

Thanks very much

shabba

shabba

[/b]

 

[Micilin]

I get what you mean, i.e. its like putting up double plasterboard (for sound proofing)making sure the 2nd plasterboard is overlapped on the 1st plasterboard so no gaps are visible. Well explained.

Yes, better analogy!




Well if you have wall to wall junctions as fillets then how would you get a good straight finished wall or is the whole point not to have one and have curved walls.

With tanking the primary goal is to keep the place dry. Any tanking carried out by a firm will make this clear, and if you want straight walls then you'd pay dearly for dobbing out on a pro rata basis.

If doing it yourself you could give it a final coat of render that did not have a fillet. Usually , but of course not always, these areas are basement or cellar applications. So a rounded corner or wobbly line is not as out of place as your front room.



How would I apply this flexible material... would i put it on the where the floor-wall meets and where the wall - wall meets? at each coat?.. or just the final coat. And also could you let me know what kind of flexible material... i know you specified skia supplyu or igas seals but i googled and nothing came up

The flex would be fixed in the first coat, so that any movement in the wall would take place behind the flex , independently of the render. This is similar to putting buliding paper onto timber before the eml mesh, making sure the eml is not nailed to the timber - so the timber /wall joint can move without craking the plaster on top .

'Supplyu' was a typo of what sika would 'supply you '

You'd best google or contact sika for their reccomendation but they use felxible polymer strip that the adhesive is applied to , this is fixed over the crack , the render sticks to the adhesive and the coats are build up as normal.

'Igas' is (or was) a strip of pitch on hessian with small granite chiipings embedded for a key . It is very flexible and malleable . Cut to size and stuck on with adhesive around services or over cracks.

Nowadays I'm sure fibreglass mesh over cracks will work, I use it in ordinary render.







The walls are very wet and the previous render was flaky. I am doing the floor aswell... what mix would you recommend here?

For the floor I would have a slurry the same as your first coat of render, well brushed into the floor. this goes over your wall render which has lapped onto the floor. Then onto this you can lay your sika screed with the sharp sand , which will cover your wall lap. I'd want at least 50mm of screed but more is better. I think this ties in with your own thoughts





1 Final question, would you recommend us doing the internal walls of the basement (i.e. the brick partition walls).

Not having seen it, standard practice would be to tank, full height , one metre from any wall that initially needs tanking ie any walls that butt your wet walls.

Bear in mind that you can't stop water, just divert it so there is a chance that water will make its way along.

Common sense says that tanking the walls 1200 up from the floor and 1200 back from the wet walls will cut out rising/creeping damp - then just render the rest with a waterproof additive.

If the walls are small tank the lot. There is a break even point of time & money versus peace of mind that you'll have to decide on yourself.

As an aside For running water, egg box membranes on the floor to screed onto might be an option

 

[Micilin]

Looking for sealing products for cracks and services anyone got any?


http://www.wykamol.com/services/damp-proofing/tanking-products/wykamol-fillet-seal.html