Patchin up me porch

[joe90]

Right, see if you can scratch the first coat with a pointy old screwdriver or something to give a key (this is why it’s often called a scratch coat!). I much prefer SBR to PVA, give the first coat a brush with it, let it dry then give a second brush and apply the final coat before the SBR is completely dry. I have even heard of adding a little SBR to the water when mixing the Mortor. Dry brush the final Mortor coat with a brush before it’s hard but still damp to give a good finish.

[zoothorn]

hi Joe. Key! that rings a bell/ the word I was after. Ok doing the screwdriver idea just seems to chip the surface crust off tho. But I can wire brush a "keyed" rougher finish (tho I'm into hellish dust city again) if that fits the bill?

 

And I dont have sbr.. so might pva be an ok 2nd best? I mean it might stick ok without, ppresumably the wetter the mix the better the adhesion/ so I'll make it a little sloppy to help if correct (as Peter hinted is better than dry presumably adhesion was the reason).. but making a mix then finnding it all falling off, will ruin a heck of alot of effort/ a mix wasted.

 

Sorry so many Q's.. bc I'm new to mortar, & turns out it's bodged up very easily if a trainee std like me. thx zH

[markc]

Chipping the surface crust is perfect, no need to wire brush.

Gobbo will stick to most things without falling off. If you are worried, mix a little and stick it to an area. let it dry and then reassure yourself it has stuck. You are pointing some old stonework, not bonding fall arrest or structural members to the wall.

[joe90]

Yes, chipped surface is better so don’t go wire brushing (and coughing all day). The wall has to be damp and the mix fairly sloppy, try mixing a little at a time to get the mixture right. Make sure the new Mortor is mixed well, try to get air into it.  If the wall is damp the action of it drying out pulls the new Mortor in so gives adhesion. 

[zoothorn]

On 15/04/2021 at 09:20, markc said:

Chipping the surface crust is perfect, no need to wire brush.

Gobbo will stick to most things without falling off. If you are worried, mix a little and stick it to an area. let it dry and then reassure yourself it has stuck. You are pointing some old stonework, not bonding fall arrest or structural members to the wall.

 

Gobbo. Do you mean spit on it, like those frightful cave people did on their hands? I think I might run out asap & dry up like a prune markc.

 

Im gonna google gobbo. Ist time Ive ever said that.

[zoothorn]

On 15/04/2021 at 09:28, joe90 said:

Yes, chipped surface is better so don’t go wire brushing (and coughing all day). The wall has to be damp and the mix fairly sloppy, try mixing a little at a time to get the mixture right. Make sure the new Mortor is mixed well, try to get air into it.  If the wall is damp the action of it drying out pulls the new Mortor in so gives adhesion. 

 

When you say damp, do you mean (I assume not me spitting all over my porch until I feint) apply a fairly sloppy 2nd coat, fairly soon after my pva solution 5;1 I think..? sorry I only have pva.

 

Its going to be a so-so job at best this, Ive made schoolboy errors every step. Im rather embarrassed tbh!

[zoothorn]

Gobbo - Wikipedia

https://en.wikipedia.org › wiki › Gobbo

 

 

Gobbo is an Italian surname meaning "hunchback".

 

..

[jfb]

I wouldn’t bother with pva.

also don’t make the mortar too wet if you are pointing (not rendering). You’ll just smear it everywhere and make a mess. 

[joe90]

1 hour ago, zoothorn said:

When you say damp, do you mean

I always brush a little water on the surface with a paint brush or little garden sprayer.

[markc]

Gobbo ... Mortar! maybe its just a yorkshire saying

[zoothorn]

26 minutes ago, joe90 said:

I always brush a little water on the surface with a paint brush or little garden sprayer.

 

Ok joe thanks I get that idea. I think I'll just do water as jfb also suggests not pva.

 

Really the last thing then is the reveals. Ive shored these 3 inside areas with mortar ok, but sides of stone here are so inny-outy I still think I need something added on to even-out the 3 surfaces, in a nice contoured way. And I can only think render, because it's a relatively thin layer needed onto the stone (& mortar isn't I don't think is ever applied in such a 'coat'.. is it?).

 

Am I on the right track here.. or not at all? If so then I think I need a mix of 6:1:1 with one of lime. Which maybe I can scrounge a big 2 handfuls of from a build site I was thinking.

[zoothorn]

Job done. I had to wing the reveals, sort of done a render.. with mortar. Whether wrong i dont know, but it'll have to do. I couldn't understand how lime could provide 'cementing' aspects (i think  cement is a verb) so how correct for me, for this job which involved alot of shoring up (stone at the reveal areas) as much as pointing, I couldn't really understand. So if its wrong I dont know, but its definitely better than it was & looks are ok.

 

Getting the white off the stone tho, for a ' natural' look.. is a no go. Its 20 mins each stone all effort fkn exhausting & will still not fully remove. So i have no option but paint over. So may as well have been mortar not lime then i think (plus, mortar surely is far stronger). Thank god done! 
 

Thanks for help chaps. Zh

 

 

 

 

 

 

 

[Onoff]

Cup brush in a 115mm angle grinder would get that paint off I reckon. Googles, mask, gloves a must and a handle on the angle grinder.

 

One stone at a time. 

 

Could look superb.

 

You never know, you might meet a 21 year old nympho into oddballs who owns her own sandblasting company! ?

 

 

[zoothorn]

1 hour ago, Onoff said:

Cup brush in a 115mm angle grinder would get that paint off I reckon. Googles, mask, gloves a must and a handle on the angle grinder.

 

One stone at a time. 

 

Could look superb.

 

You never know, you might meet a 21 year old nympho into oddballs who owns her own sandblasting company! ?

 

 

 

Hi Onoff. The slate is very prone to chipping, I think soft might be the word.. so I'd be very wary about attacking with said tool.

 

But I do like the nympho idea. Friend next valley has a sandblast rig I believe.. wouldn't it unnavoidably fire out all my mortar work tho same time?

[zoothorn]

I wonder if there's a small mega stiff brush attatchment for a drill driver- anyone know? A wire brush, as hard as I could, was only shifting some.. the rest it couldn't have affect on. thats how welded on it is.

 

 

[Onoff]

1 hour ago, zoothorn said:

 

Hi Onoff. The slate is very prone to chipping, I think soft might be the word.. so I'd be very wary about attacking with said tool.

 

But I do like the nympho idea. Friend next valley has a sandblast rig I believe.. wouldn't it unnavoidably fire out all my mortar work tho same time?

 

Sandblasting is quite controllable over a small area tbh. 

 

1 hour ago, zoothorn said:

I wonder if there's a small mega stiff brush attatchment for a drill driver

 

Like this?

 

https://www.screwfix.com/p/crimped-wire-cup-brush-50mm/843jg

 

Goggles and gloves, goggles and gloves!

[zoothorn]

25 minutes ago, Onoff said:

 

Sandblasting is quite controllable over a small area tbh. 

 

 

Like this?

 

https://www.screwfix.com/p/crimped-wire-cup-brush-50mm/843jg

 

Goggles and gloves, goggles and gloves!

 

In fact I was just on this very screwfix item an hour ago.. Id seen them, but never actually known what jobs they were for.

 

Great will get one & see how I go. yup with serious goggle action. If no good I might see if friends sandblast rig I can borrow.. but its quite 'hairy chest' with the diving helmet etc for a newbie/ trainee herbert like me.

 

thanks zH

 

[Onoff]

55 minutes ago, zoothorn said:

 

In fact I was just on this very screwfix item an hour ago.. Id seen them, but never actually known what jobs they were for.

 

Great will get one & see how I go. yup with serious goggle action. If no good I might see if friends sandblast rig I can borrow.. but its quite 'hairy chest' with the diving helmet etc for a newbie/ trainee herbert like me.

 

thanks zH

 

 

I've dabbled with sand blasting. WHEN it worked this Parkside gun was alright. Random video on it:

 

 

It kept jamming and before I knew where I was I got the hump and tried to "fix" it. No good now! ?

 

I tried making a sand blasting gun too...FAILED!

 

I've then bought an eBay gun that sucks up the blasting sand from a barrel (btw, any sand, grit, crushed glass, soda crystals, walnut shells etc used for blasting is called "media" or "blasting media"). That too started off great then clogged.

 

My problem was moisture in my air supply or sand or both I think. 

 

Don't btw use builder's sand, play pit or block paving sand etc. You risk developing silicosis! ? Only use proper blasting media. I bought 50kg from a commercial blaster's I've used for work and private, paid for jobs. Even then, wear a mask!

 

 

 

 

[zoothorn]

@Onoff jesusH those things are viscious.. I think this might be overkill & a bit scary for muggins! mind you, friend had some bloomin great helmet affair with pipe sticking out back like off alien or something.. very scarier. Very good value mind you by all accounts. (did he say compressor was 19.99.. or 99.99?)

 

I'll see how I get on with the 50mm wire whatnot 1st.. thought these were for shoes/ cobbler tools, the only place Ive ever seen one on end of a lathe spinny thing fk knows what.

 

If I do have success, then it'll be a shame to have gone the 4:1 cement mortar route I took (cos I was adamant stone needed whitewashing, due to welded on old paint).. but I think the reveals must benefit from the cement mortar: now I'm not worried about lintel stones raining down.

 

I'm still none the wiser on how lime can become solidly "cemented" just with sand & water tho. I can only surmise it's nothing like as strong as cement mortar tho-?

[Onoff]

I you leave a bag of lime long enough it reverts to a sort of limestone i.e hard. Interesting reading here:

 

https://www.buildingconservation.com/articles/cement/cement.htm

 

I'm still waiting to grow a pair and do the flint infills in my brick pillars. 

[zoothorn]

23 hours ago, Onoff said:

I you leave a bag of lime long enough it reverts to a sort of limestone i.e hard. Interesting reading here:

 

https://www.buildingconservation.com/articles/cement/cement.htm

 

I'm still waiting to grow a pair and do the flint infills in my brick pillars. 

 

Good link that- appreciated. I think the word in question then.. is calcification: both regarding what lime mortar does, and, what I think I've had to battle with the whole afternoon: bought a 50mm wire whatnot. Burnt out a drill, only got 2sq ft done, & the remainder is not even shifting with a 480w drill with this thing on at max torque. Totally exhausting with very little to show for it. So I'm stuck.

 

The white god knows what (definitely old.. maybe 1830) is not welded on, its worse.. it's calcified-on the stone face I think. It is nigh on -impossible- to fully remove. An utter b'stard job. Hmm..

[Onoff]

4 minutes ago, zoothorn said:

 

Good link that- appreciated. I think the word in question then.. is calcification: both regarding what lime mortar does, and, what I think I've had to battle with the whole afternoon: bought a 50mm wire whatnot. Burnt out a drill, only got 2sq ft done, & the remainder is not even shifting with a 480w drill with this thing on at max torque. Totally exhausting with very little to show for it. So I'm stuck.

 

The white god knows what (definitely old.. maybe 1830) is not welded on, its worse.. it's calcified-on the stone face I think. It is nigh on -impossible- to fully remove. An utter b'stard job. Hmm..

 

You can find that with the drill rotating one way constantly it "smooths" out the wire brush. Pays to reverse the drill rotation now and then.

 

Goggles and gloves, goggles and gloves! 

[Onoff]

Just now, Onoff said:

calcification

 

Liked that bit of a change mind for David Duchovny after the X-Files...

[zoothorn]

1 minute ago, Onoff said:

 

You can find that with the drill rotating one way constantly it "smooths" out the wire brush. Pays to reverse the drill rotation now and then.

 

Goggles and gloves, goggles and gloves! 

 

No I mean a leccy 480w drill that can't reverse. No chance with a drill driver. Whole thing smoke pouring-out bushes fkd ruined.

 

This approach will not work. Thankfully only £2 fot the brush.. but a useful drill that was. My fault.

 

Its turned into job from hell. dust mainly.. but this wretched white ruining the stone, & how to get it off compounds it. A month on it now (I bet an afternoon for you guys).

[Onoff]

Brick acid like Disclean? Again be bloody careful and wear non absorbent gloves and GOGGLES if not a full face shield. 

 

It's not salts leeching out of the stone is it?