Stripping paint off deep pebbledash - any ideas?

[Eric The Viking]

We moved in here almost eighteen years ago.

The house dates from around 1905, and has really deep pebbledash ("boulderdash"). It was whitewashed, I think just a lime wash of some sort, which was on the way out.

I jetwashed it, and painted it by hand (rollers and spraying are almost impossible), with a decent "Sandtex" masonry paint. It took around nine months, 27 "buckets" of paint (yup, almost 700 litres), and almost all my spare time, mainly because the pebbledash is so deep (progress is very slow). I think the surface area is around 3x-4x what you'd expect from the building dimensions, and it's got 'pockets' and all sorts in the finish (from when it was first done).

The actual cement is stuck fast, but my 17-year-old surface coat is failing (I know, I should have redone it a long time ago). Where it's cracked, water is getting in, and, because we have solid walls, that means penetrating damp. Where the Sandtex hasn't cracked, though, it's like elasticated concrete. And that's the main problem, as I see it.

Getting the damaged surface off is going to be tricky and this time I'm not sure a jetwash will hack it. I have to make a start soon, or it won't get done this summer. And another wet winter will cause big problems.

Has anybody got any suggestions for getting it back to a stable surface for repainting?

Thanks,

E.

 

[Phil Pascoe]

Plaster it.

 

[Mark A]

I'd rather hack off roughcast and re-render than go through the frustration of painting the stuff again. Dabbing on paint with a 1" brush was the most soul-destroying, monotonous job I've ever done

 

[CHJ]

Think you only recourse is a sand/glass or plastic bead blast.

 

[AndyT]

One possible approach, avoiding the need to remove the existing finish, would be to have someone re-render using K-rend, over supporting mesh which they will have screw-fixed to the walls. Not a diy job!

(K-rend is a modern breathable render of great strength which is self-coloured through the whole thickness. There's a lot about, once you know how to spot it!)

 

[Mike.S]

One concern I'd have is whether the 'Sandtex' paint was a typical modern 'plastic' paint which didn't allow the walls to breath. The better finish would be something like a limewash. Might the existing coating be removed with sand blasting? Then look at repairs to the render before refinishing. On latter I'd consider use of an airless spray gun.

In case it's of interest (no connection etc):

Building Conservation

Heritage House

 

[Eric The Viking]

I have a wet sandbladsting attachment for the jetwash that I've never used (it sucks up from a bag of dry sand). It would probably work but is likely to be very messy though.

I'm contemplating a needle gun, of the type used by welders for cleaning steel of rust.

I'm horrified at the thought of getting quotes to get it re-rendered, never mind that it won't match in (it's a semi- albeit a big one). Last time it was patched, we used a sack of actual pebbles, rather than any sort of Tyrolean flinger or whatever.

 

[Mike.S]

I have a wet sandbladsting attachment for the jetwash that I've never used (it sucks up from a bag of dry sand). It would probably work but is likely to be very messy though.

Baking Soda instead of sand?

See here and here.

 

[rafezetter]

I have a wet sandbladsting attachment for the jetwash that I've never used (it sucks up from a bag of dry sand). It would probably work but is likely to be very messy though.

I'm contemplating a needle gun, of the type used by welders for cleaning steel of rust.

I'm horrified at the thought of getting quotes to get it re-rendered, never mind that it won't match in (it's a semi- albeit a big one). Last time it was patched, we used a sack of actual pebbles, rather than any sort of Tyrolean flinger or whatever.

This will be extremely effective at cutting off the sandtex, and will also clean up the stone underneath a treat , just make sure you play the target area and don't hover too long in one spot as it will also cut holes in walls! - (the fire services have equipment whereby they use a high pressure water jet like this with sand in to cut holes through walls into otherwise inaccessible areas to put fires out) - it will also "polish" the whole thing which might leave an effect you can live with and no other treatment required.

Sure it'll create a helluvua mess now, but will still be the quicker option compared to 9 months painting (OIK! :shock: )

After that I'd go back to limewash which you can practically throw on as sloppy as you like.

 

[Dee J]

I'm faced with a similar problem...
Ours is a roughcast render (splattered concrete out of a Tyrolean? applicator). Sometime prior to our purchase it was sprayed with a thick coat of a plastic paint (bet it had a lifetime guarantee.....). Well it's lifespan is up, some areas peel away with no noticeable adhesion - whereas other areas are stuck fast. The goop is so thick that the differences in texture are bound to show through any new paint. The render is very hard and in good condition. Anyone tried a needle scaler gun on this stuff?
Dee

 

[woodfarmer]

I would use a wet water powered sand blast to clean it. Once clean and dry spray Thompsons sealer on the walls (use a paraffin gun).

 

[billybuntus]

Having just sand blasted the front of my house with a wet system (water and grit) I'd say give your jetwash a go but you may find it painfully slow and it may not even be effective.

I blasted limestone and needed a compressor that supplies 100 psi at 200CFM (Huge diesel compressor).

If you do try it and it's effective, try and buy grit from a blasting supplier. It's around £8 for a 20kg sack as opposed to the kings ransom the likes of machine mart will charge you for a 10kg bucket.

 

[Eric The Viking]

Having just sand blasted the front of my house with a wet system (water and grit) I'd say give your jetwash a go but you may find it painfully slow and it may not even be effective.

I blasted limestone and needed a compressor that supplies 100 psi at 200CFM (Huge diesel compressor).

If you do try it and it's effective, try and buy grit from a blasting supplier. It's around £8 for a 20kg sack as opposed to the kings ransom the likes of machine mart will charge you for a 10kg bucket.

Thanks for that - I'm very nervous about the cost and mess it will make. I have some to do ASAP so will probably experiment.

Cheers,

E.

 

[devonwoody]

I would suggest you definitely confirm what the rendering is covering before doing anything. I have seen disasters when rendering was removed to find it was attached to chicken wire attached to timber framing and the inside wall was the only brick not the outside.
A neighbour recently had his rendering hacked off but the builder would also not hack off some areas near windows at corners in case of structural accidents etc.

Sorry to be negative.(I had mine hacked off, 300sq.ft on one wall and cost £1000 to rerender and that was cheap)

 

[Eric The Viking]

I know what it's covering... sadly :-(

 

[whiskywill]

One possible approach, avoiding the need to remove the existing finish, would be to have someone re-render using K-rend, over supporting mesh which they will have screw-fixed to the walls. Not a diy job!

(K-rend is a modern breathable render of great strength which is self-coloured through the whole thickness. There's a lot about, once you know how to spot it!)

A neighbours house, built about 3 years ago, was finished with K-rend and it is the greenest house around. It certainly knows how to attract algae.

 

[worldwiser]

Eric, am in a similar situation. 10 years later.. Would be keen to find out how you got on? I’ve just manually scratched off some plastic Sandtex which barely clings to our roughcast render which is solid as rocks. But I’m never going to do the whole house like that! Be good to hear from you. Cheers, Simon

 

[Sideways]

@worldwiser .
Eric hasn't been on the site in 4 years so don't hold your breath waiting for him to reply.
Hopefully this catches the eye of another UKW member who can offer you some advice.

 

[Jake]

The best solution is probably TORC or JOSS, but as I couldn't find anywhere to rent those I used a mix of Peelaway and a hired diesel dry steam cleaner to strip the bath stone on the facade of my house of 150 years of paint.

Rented from these people (this isn't the machine I rented but their current equivalent)
https://bgclean.co.uk/product/red-mist-steam-pressure-cleaner