I`m about to re-point my detached brick garage and am seeking advice on the correct mortar mix etc to use.
One of my neighbours did a similar job 4f years ago and some of his replacement mortar is crumbling and coming out of the joints, especially around the lower blue brick damp course.
Also is it wise to use PVA as a bond?
Thanks
I'm by no means an expert on the subject, but here's what's worked well for me. Use a strong mix of soft sand and cement, around 3:1-4:1. Add some integral water/frost proofer to your gauging water. Also add PVA to the gauging water at about 25%. I find this gives a very nice, smooth mix even at low water content.
Mix it fairly stiff, but wet enough so that the mix doesn't 'crack' when handled.
Wet the area you're about to render/point, either with water or pref. with 25% PVA.
If the building is made from soft brick, and lacks good foundations and expansion joints, eg typical Victorian construction, then the mix above should not be used, as it is likely to result in damaged and broken bricks. So it does depend what you have. Victorian built garages do exist, as do more modern soft brick ones, so I cant assume this is not an issue.
Also the wall face should not be PVAed as it increases dampness in the wall. But again, whether that is a real world issue depends on the type of construction: for some it very much is, for some not.
For Vic walls 1:1:6 is commonly recommended.
Regards, NT
Ok, fair point - I've only used the above on stone and concrete block.
Nor me; however, doesn't the nature mortar mix depend on factors like the age of the building, type of bricks, how it was built in the first place etc? My understanding is that, for example, if you use too hard a mix than was intended, and/or which is impervious to water, you're likely to cause severe future damage, isn't that right?
David
In which case why use so much PVA it isn't an ingredient I've ever used in mortar. If the brickwork is dry wait for damp weather and wet the wall thoroughly then apply the mix. Make sure you have hacked out enough depth to give a key. And wet the wall as you move along every time it looks dry.
What is important is that the pointing dries slowly. That is why a weakish mix is preferabe.
Another problem is using fairy liquid or similar in the mix. Use no detergent. It will be stronger if you use no Feb or similar too neither. Harder to work though.
If the mortar is stronger than the bricks, and the building is prone to movement, as Victorians are, the weakest links break... the bricks. Much better to have the mortar break, thats easy to fix. Vics generally have very soft bricks, little foundation and no expansion jonits, hence movement is routine.
I'm sure there arent a lot of Vic garages about, but I have seen them.
Regards, NT
I believe the *correct* amount of detergent actually makes a stronger mix. Proprietary plasticisers, however, are not true detergents but very small particle size salts. IMO pva simply takes the guesswork out of the equation. How porous is the surface, how wet does it need to be etc.
They were called coach houses then. None of this French rubbish.
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