Rendering internal plinth

[tobydog]

Well, I haven't been too idle this long weekend. I mixed up my first ever batch of lime mortar / render and maked like I was icing a cake. The wall was very lumpy and broken so I stabilised the face first. I hope the pictures below show that I didn't do too bad. The problem I had was the inconsistancy with the batches I made. The first picture shows it as quite dry and sandy whilst the second was wetter and less sand. Not intentional although I think my problem with the second batch was that I tried making twice as much and didn't quite mix it properly. I came across some fairly dry bits and had to add more water which unfortunately made the overall batch too wet. I think I saved the day and no cracks so far.

My problem is picture three. The house has had some unsympathetic work done in the past and you will see I've come across some block work. I tried wetting it but water just soaks in like blotting paper and disappears. Is there a trick to making sure lime render sticks to dry blocks or do I just soak them? Is mesh the answer.

Thanks

 

[tobydog]

Sorry but wrong pictures attached. These are the correct ones

 

[billybuntus]

I don't know a lot about lime render but if you require the blocks to be damp just use a mist sprayer before applying the lime. Just after you've mixed it would be ideal.

The bricks\wall will soak up the water like a sponge.

 

[angrybird]

looks to me like you've done a pretty good job tobydog
keep up the good work x

 

[GRADE_II_MONEYPIT]

Looks good, I would have purchased pre-mixed knocked up mortar/render to ensure consistant mix (I know is costs more but it is cheaper than re-visiting a job if it doesnt stand test of time).

When I assisted my stonemason he made the mixing look so simple.

You have also inspired me to tackle (or at least try) my cellar walls myself that will be lime plastered and lime washed.

Keep up the good work.

 

[tobydog]

I used a garden sprayer on the bricks and existing lime mortar and they soaked up quite a bit of water. Some parts were drier than others so the uptake also varied. I'm just concerned how much water the blocks are sucking up as it's never ending and I'm looking for an alterantive.

Thanks angrybird. I like the way I've managed to build in that 400 year old look :wink: It will all be lime washed with several coats so hopefully many of the 'bad' imperfections should be lost.

I did look at pre-mixed but I thought the lime might separate from the sand in the bag which would make it awkward to use part measures. You'd need to use the whole lot in one go to get the ratios correct. Maybe someone else can comment on this. Also, as mentioned, it does work out surprisingly more expensive given that the sand is so cheap and makes up the majority of the pre-mix.

I also felt inspired to try this because of what others were doing. Let's face it, if it's rubbish I'll take it off and try again. It's surprising how quickly you learn what to do and what NOT to do :roll: .

 

[tobydog]

GRADE II MONEYPIT - looking at your post again you mention pre-mixed 'knocked up' mortar / render. I didn't realise you could actually buy that. I thought pre-mix was just dry sand / NHL in a bag. I considered the non-hydraulic putty that you knock up but don't you need to mix sand with that which would still leave me with the same ratio problem? I just need to be more careful next time. I recall I was being harrassed by the chickens at the time that were trying to eat the lime :roll:

 

[plasticpigeon]

Well done for having a go. I'm sure that some of the old methods have been lost in time, and it can be no bad thing to experiment, so long as you don't live with the failures! Looks ok to me though. I shall be doing much the same next week. wishh me luck.

 

[GRADE_II_MONEYPIT]

GRADE II MONEYPIT - looking at your post again you mention pre-mixed 'knocked up' mortar / render. I didn't realise you could actually buy that. I thought pre-mix was just dry sand / NHL in a bag. I considered the non-hydraulic putty that you knock up but don't you need to mix sand with that which would still leave me with the same ratio problem? I just need to be more careful next time. I recall I was being harrassed by the chickens at the time that were trying to eat the lime :roll:

I think the non hydraulic pre-mixed lime mortar knocked up in buckets is ready to use? (but not 100% sure)

See example here http://www.lime-mortars.co.uk/lime-mortar/non-hydraulic/10kg would be intetested if anyone used this before and whether wet or dry

The hydraulc mortar offered by same company says "Ready to mix, just add water" http://www.lime-mortars.co.uk/lime-mortar/hydraulic/NHL3.5/15kg

 

[robgil]

I would soak the blocks as much as I could without being silly about it and plaster over the lot. Are you using hair in the mix?
Also I would give it a spray with the mister periodically or whenever it looked as if it were dryish. Dont worry about keeping it too wet, it wont do it any harm, just dont wash it off. Looks good though and any inconsistencies in the finish will soon disappear under a few coats of limewash.
I never did see the point in buying premixed stuff but then again I have never used it.

 

[tobydog]

Thanks Rob. I haven't used hair so far because the plinth was so rough and damaged when the cement came off that there was plenty for the new render to lock into and hang onto. I'll make up a small batch and have a practice on the blocks and see what happens.

 

[eezageeza]

Those lightweight blocks are like sponges - I once laboured for a builder rendering over some of those on our house, and he had me training a hose on them for several minutes before he agreed they were wet enough to plaster! It was an external wall BTW, so the runoff wasn't an issue!

 

[tobydog]

Thanks eezageeza. Given that I've just spent the past 6 months drying this room out , I may give the hose treatment a miss. I'll think about it and hopefully procrastinate long enough for my holiday to turn up first .

 

[stuart45]

Use a brush and bucket of water. It's easier to control the water by dipping and flicking it on. You need to damp down the thermalites a bit. I've just finished plastering the blockwork on my new extension, but as it's a new build with cavity walls I was able to give them a couple of coats of 3/1 water/PVA to help ease the suction.

 

[tobydog]

Well, I had a practice on the thermalite blocks. Thankfully there are only three to cover but there would have been much less if I hadn't got carried away when taking off the gypsum. I wanted to remove it up to what I thought was a previous damp tide mark but now that I'm drying the wall on the outside I probably needn't have gone so high. We live and learn.

Anyway, given that the existing gypsum plaster / board is about half an inch thick, I thought that might be too much lime render to apply in one go on a far from perfect base. I sprayed water onto a small areas four time, each time taking longer to soak in. After the fourth I quickly applied a thin scratch coat whilst the surface was still wet and worked it quite hard into the surface. Obviously this dried out very quickly, however, it is clinging on pretty well and looks to be a perfect base for the top coat. I will hardly be a calamity if it doesn't work but I'll let you know.