Sealing blockwork of brick & blockwork house - render alternative?

[readiescards]

A bit late in the day but I've decided to swap from a cold to a warm loft, using Icynene under the felt between the trusses.  However I also now realise I need to seal the  inner blockwork to help give some air-tightness.

Current options:

* cement render the blockwork - maybe plastering later, should I convert the attic to a habitual space in the long term future

* 1 part water to 4 part PVA mix hand painted onto the block work - tedious and there are 4 large gable ends to do, unknown long term consequence of doing so

 

What are the options to seal the inner blockwork to increase air tightness?

(Does not need to be particularly pretty)

 

Thanks

Paul 

[Russell griffiths]

Can you not Parge it with a slurry, this way if you want to plaster later it will already have a nice key. 

[readiescards]

Whats the difference between a parge coat and the first layer of a render and skim coat please? 

[Declan52]

Parge coat will be a few mms depth of watery cement sand mix slapped on with a paint brush. No real skill required and it's messy.

Scratch coat maybe 10-15mm deep depending on how plumb the wall is and involves a lot of skill to get it right. 

[PeterW]

6 minutes ago, Declan52 said:

Parge coat will be a few mms depth of watery cement sand mix slapped on with a paint brush. No real skill required and it's messy.

 

 

Or a couple of cheap plastic sweeping brushes and a couple of washing up bowls works just as well

[Russell griffiths]

We put it on with a hessian sack and a pair of rubber gloves, you can push it into any joints that weren't full and you tend not to drop as much as with the brush,but both work very well. Try it both ways. An old fashioned hairy type broom head rather than a synthetic modern broom works better. 

[readiescards]

13 hours ago, Russell griffiths said:

We put it on with a hessian sack and a pair of rubber gloves, you can push it into any joints that weren't full and you tend not to drop as much as with the brush,but both work very well. Try it both ways. An old fashioned hairy type broom head rather than a synthetic modern broom works better. 

Gosh any photos of the action?!

[readiescards]

On 13/02/2017 at 07:24, Russell griffiths said:

We put it on with a hessian sack and a pair of rubber gloves, you can push it into any joints that weren't full and you tend not to drop as much as with the brush,but both work very well. Try it both ways. An old fashioned hairy type broom head rather than a synthetic modern broom works better. 

 

Can you explain the hessian sack method in a bit more detail please? Are you squeezing it through the sack?

[Russell griffiths]

No. Mix it up a bit sloppy, put a rubber glove on as the cement is not good for your skin, cut a hessian sack down so it goes over your hand, grab a good hand full and slap it on swirly pattern or figure of eight is good squish it in all the nooks and crannies. Helps if you put a bit of plastic on the floor. 

Messy but quick a soft old fashioned broom head is good as well, not the new plastic bristled type. 

[stepheni]

what kind of ratio for this sand/cement sloppy mix?

[Russell griffiths]

5:1. 4:1 it really isn't that important just to fill in any voids air pinholes. 

We used to do it to provide a better key before rendering on a poor surface. 

[bassanclan]

I used Gyproc Soundcoat plus, paddle mix with a bit of water and coir broom, mix to the consistency of emulsion paint and "paint" the walls with it as fast as you can, it will go off in 30 mins.