Mortar on wall ties

rampantbunny

I've seen it written that wall ties should be kept clean (no mortar droppings) to allow the drip to perform as it should.

In reality is this possible?

My cavity is not what I'd call dirty and I keep the bottom flushed out regularly to stop build-up, but its inevitable that mortar will fall down and stick to the ties. I'd say most of them have some dirt on them at this stage.

BarneyMc

I went around mine as often as possible to knock off what I could. The longer the mortar sits there the harder it gest to remove. Is your insulation going in with the blocks or are you pumping beads?

rampantbunny

I'm pumping beads Barney. Does this mean it doesn't matter, or makes it more important?

Going around the house and wiping the mortar off only works when you can reach the ties, but at some point you just can't reach anymore.

My plasterer just commented on it at the weekend when he looked into the cavity. I didn't think there was anything a block layer could do about it so said nothing.
Just had a thought now that a spray of water down the cavities after a days work would have kept the ties clean.
There's my question answered really...I've a long hose on site for them to rinse out the cavities so no excuses really.

BarneyMc

I cleaned them as much as I could to reduce thermal conductivity and also for the drip performance. Not having the rigid boards just makes it easier probably. I would limit the spray as this might wash out some mortar?

rampantbunny

Not a spray as such but at least giving a quick once over straight down from the top. Ties are stainless steel. As long as the mortar doesn't attack the metal over time I'm OK with it, but how would i know really.
One of those things I'll just have to ignore now, and move on.

sydthebeat

rampantbunny wrote: »

I'm pumping beads Barney. Does this mean it doesn't matter, or makes it more important?

Going around the house and wiping the mortar off only works when you can reach the ties, but at some point you just can't reach anymore.

My plasterer just commented on it at the weekend when he looked into the cavity. I didn't think there was anything a block layer could do about it so said nothing.
Just had a thought now that a spray of water down the cavities after a days work would have kept the ties clean.
There's my question answered really...I've a long hose on site for them to rinse out the cavities so no excuses really.

good way to check that all your dpcs work properly

Clseeper

Good at least I'm not the only one.... I've gone around every morning on site reaching into the cavity from the opes to crumble off the any mortar that has fallen down.

If I remember from my calculations, the added increase in U value from the SS ties wasn't massive (~0.01). So I'm not too worried about the small bits of mortar adding too much extra - as long as it's not on all the ties.

Also my blocklayer is building up the outer leaf first so any mortar droppings are normally on the side of the tie nearest the inner leaf & past the drip lip so hopefully that will help there. Also mine is a 250mm cavity so a long distance for water to traverse.

I still intend to continue my morning routine but it more me being pedantic than any serious fear.

rampantbunny

sydthebeat wrote: »

good way to check that all your dpcs work properly

It's wetter inside some days than outside, so I'd need to be on my game to spot water coming in.

Right, I'm off to get some sort of acid and let fly into the cavity...clean it all out good and proper

rampantbunny

Clseeper wrote: »

Also my blocklayer is building up the outer leaf first so any mortar droppings are normally on the side of the tie nearest the inner leaf & past the drip lip so hopefully that will help there.

Would have thought the mortar nearest the outer leaf was not as important.
Caveat; I generally don't have much of a clue so the following could be completely off, but to me makes sense.


The wall ties should slope down towards the outside leaf. If water travels down the cavity and onto wall ties, it needs to make its way out towards the outside leaf. It hits the drip and falls off. The mortar before the drip (nearest the inner wall) will force the water to drop off at this point, therefore the water never makes it out as far as it should.

BarneyMc

rampantbunny wrote: »

Right, I'm off to get some sort of acid and let fly into the cavity...clean it all out good and proper

Why use acid? Would it react with the ties or mortar?

Clseeper

My thinking would be that there is a higher chance of water leaking in from the outer leaf (crack in plaster, water caught by lapped DPC over windows, driving rain etc) so the tie drip is to stop the water traversing from the outer leaf to the inner leaf?

rampantbunny

BarneyMc wrote: »

Why use acid? Would it react with the ties or mortar?

You might have missed the smiley face Barney. No acid will be used in my build.

BarneyMc

rampantbunny wrote: »

You might have missed the smiley face Barney. No acid will be used in my build.

I will sleep tonight then ;-)

rampantbunny

Clseeper wrote: »

My thinking would be that there is a higher chance of water leaking in from the outer leaf (crack in plaster, water caught by lapped DPC over windows, driving rain etc) so the tie drip is to stop the water traversing from the outer leaf to the inner leaf?

You could be right. The science of the wall tie is complicated it appears.
You'll be fine with a 250mm cavity I'm sure. Mine is 200mm but I'm still not really worried.
Spoke to block layer last night and he said he'd just give the ties a slap of a stick when finished. Gave me an awful image of ties being bent ties all over the place.

Clseeper

Ah the old school blocklayers - have one on site myself. It's all new to them (wdie cavity etc) but he's real open to learning and has taught me a few things too.

The stick sounds a bit extreme alright - I think I'll do that part to be sure.
Good luck with the rest of the build.

just do it

For the ones you can't reach a gentle swinging chain will knock the mortar off

hexosan

I used a 6m length of rebar

rampantbunny

In all the posts I've read on boards I've never seen any mention of the cleaning down of ties.
Should've been swinging a chain or rebar from the start. Will see what the block-layer is able to do with his stick.

A wall tie with a sharp upper edge would help to minimize the surface area exposed to falling mortar. Dragons Den anyone.

sydthebeat

how its supposed to be done

touchdown77

check these out, taken from recent construction of a garage.

rampantbunny

...never even thought about looking into the garage cavities.

It was the quickest bit of block laying my plasterer neighbor has seen in a long time apparently with 5 fellas on the job. And I don't think any of them was the designated cavity cleaner either :rolleyes:

hexosan

You could just cut a length of ply slightly smaller than the cavity width and the block simply slides it along the ties as the laying the block.
I think I seen on here fclauson done that.

rampantbunny

hexosan wrote: »

You could just cut a length of ply slightly smaller than the cavity width and the block simply slides it along the ties as the laying the block.
I think I seen on here fclauson done that.

There are ways of doing it properly and cleanly no doubt, but to be fair I don't think it should be down to me or any client, to have to cut ply for the pro's.

I'll see how the stick approach fares out for them. Might get a stick of my own if it doesn't.

just do it

hexosan wrote: »

You could just cut a length of ply slightly smaller than the cavity width and the block simply slides it along the ties as the laying the block.
I think I seen on here fclauson done that.

That's what's recommended as the standard practice in the homebond blue book (bible). However how sure would be that it would be done while you're not around? I basically told them before starting what I expected of them and they heard the same message from the contractor, engineer and architect as well. As far as I'm concerned I'm paying for a clean cavity and it's up to them how they do it.

just do it

By the way the way my lads have done it is be careful in the first place and then at the end of the day they wash down the cavity. Sure it means there is some cement at the bottom of the cavity but it's minimal. And there's no mortar snots.