render mix ratio and best sand
- Thread starter boo
- Start date
- Status
Rigsby
TPF Special Forces
The mix is a bit strong for plain faced render but ok for dashing. For plain render I would use a 5:1 scratch and a slightly weaker second coat mix. Stronger mixes are ok for winter to make it set but too strong a mix in summer can cause crazing. Not initially visible until it rains and then starts to dry out showing the cracks full of water.
allthegear
New Member
Hi, I am a total beginner to rendering with lots of interest and enthusiasm to learn but little time or money. I've rendered both sides of my new 7N breeze block garden wall and broken most of the rules above in the process. Base coat was 3.5 sharp:3.5 builders:2 concrete:1 lime and Outer coat was 3 sharp:3 builders:2 concrete:1 lime. I _now know my mix is too strong and outer mix should be weaker than base. 1/2 the wall has 1 coat and 1/2 has 2. The sections with 2 coats of render is already dried and outer mix of 1 section with 2 coats post-rain has a few cracks and 1 section pre-rain has 1 crack so far. The sections with 1 coat did not crack at all and several weeks have passed since I finished those. I really don't have the time, money or patience to chip it all off and start again and I don't want to weaken my wall in so doing either. Given my circumstances, I would appreciate some advice on getting the most from this enthusiastic beginner's effort... Q1) Will painting with Sandtex before the next rain help reduce cracking? Q2) How do I best fill the cracks? Q3) Will the cracks continue to appear on an ongoing basis? Q4) Any other recommendations you can give me. The wall is topped with coping complete with drip groove. I am about to start painting the pre-rain walls as I believe this will do those less harm than rain then summer sun _and will offer some protection from rain thereafter. I already know that ideally I should have paid someone who knows what they are doing or done more preparatory reading but both would have been difficult and more reading is an afterthought. For the remaining walls I plan to use 4 sharp:4 builders:2 cement:1 lime. Any advice on how to make the most of this absolute beginner's effort without starting from scratch would be very much appreciated. Many thanks. :RpS_unsure:
allthegear
New Member
Actually, it looks terrific at the moment but it hasn't rained yet during/after which I know things will go some distance south :RpS_laugh: I've slapped a coat of Sandtex on the areas with strong mix and I'll wait to see what happens. I imagine that pro renderers will have been tasked with jobs where the original renderer has used too strong a mix but the owner can't afford to redo the whole area?. I would appreciate any insight and experience on whether I should expect most, all or just the start of any (the) cracks to appear after the first set of rain and dryout which is due over the next couple of days, the best way to deal with said cracks without redoing the job and what extent of cracking I should expect given the mixture and north UK climate. I will not be building said fence so, while it pains me to entertain the idea, will a 2.5 lb mallet and bolster be the best thing to use
allthegear
New Member
... if the cracking gets so bad I can't stand it? Note this is a garden wall not the Taj Mahal so I can live with a few minor cracks.
- Status