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epsilonGreedy

Plan C, leave aircrete walls naked for a winter?

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Having been thoroughly beguiled by thin-joint block work last week but not confident enough to load a finished roof onto such a single skinned structure I am now tempted by the thought of adopting thin-joint blockwork for both inner and exterior walls. The incentive for adopting thin-block completely for all masonry elevations is that it improves my chances of getting to a weather-tight shell before winter weather holds up my build.

 

The schedule I am now contemplating would mean leaving my exterior celcon blockwork exposed to the elements for a whole winter until brick slip cladding in the spring. I will contact H+H for an official technical opinion but would be interested to hear some community opinion.

 

Update: Just spoke to HH who did not offer any standard advice, system or partner product suggestion for hanging brick slips. I did learn that their exposed aircrete block could suffer from winter weather due to surface moisture coupled with freezing. Their recommended cladding hanging limit is 29kg per m2 which is separate to the per fixing pull load limit of 7kn. I got the impression that the typical cladding material on light blocks is modern clapboard or render.

 

The Weatherby cladding people were more switched on but unfortunately their brick slip range is very limited and it looks like they target mundane commercial buildings 

Edited by epsilonGreedy

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Are you tied to having it look like brick or could you plaster it up or combine plaster and timber cladding.

Can't remember who on here went with brick slips but they had a lot of issues with them.

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49 minutes ago, Declan52 said:

Are you tied to having it look like brick

 

 

Defo a very strict requirement for a specific brick finish. Some English bond as well which might rule out the backing sheet system used by @PeterStarck.

 

52 minutes ago, Declan52 said:

Are you tied to having it look like brick or could you plaster it up or combine plaster and timber cladding.

Can't remember who on here went with brick slips but they had a lot of issues with them.

 

You might be thinking of this thread where @jack explained frustrations encountered.

 

 

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1 hour ago, epsilonGreedy said:

 

Defo a very strict requirement for a specific brick finish. Some English bond as well which might rule out the backing sheet system used by @PeterStarck.

 

I don't know why the brick slips I used would have to go on a backing board. They are only stuck on with what looked like exterior tile adhesive. The only thing I can think of is possibly different expansion rates but then a flexible adhesive should sort that out.

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1 hour ago, PeterStarck said:

I don't know why the brick slips I used would have to go on a backing board. They are only stuck on with what looked like exterior tile adhesive. The only thing I can think of is possibly different expansion rates but then a flexible adhesive should sort that out.

 

This was my original thought but the maths is worrying. Say 2kg a brick x 0.15 (15 mm thick slip) x 60 bricks per meter = 18 Kg of slip weight per meter. Well below the 29kg limit quoted by the Celcon tech department today but even so it makes me wonder if Plan-C is a runner. 

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Unless you buy your own Kwikstage scaffold, you will end up with a lot of additional cost with this approach. Two skins of block and then the slip system means  you will need to either keep the scaffold up over winter (expensive if not owned) or drop it and then have it rebuilt. 

 

Last time I checked, handmade slips were coming in at £1.15-£1.60 each, so basically more expensive than bricks. 

 

If you want to go slips and DIY then seriously consider swapping to ICF as that is DIY build and gets you up to roof a lot quicker but does have its drawbacks.  

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14 hours ago, epsilonGreedy said:

 

This was my original thought but the maths is worrying. Say 2kg a brick x 0.15 (15 mm thick slip) x 60 bricks per meter = 18 Kg of slip weight per meter. Well below the 29kg limit quoted by the Celcon tech department today but even so it makes me wonder if Plan-C is a runner. 

I don't quite follow your calculations but my brick slips weigh 400g each.

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If the desire to be watertight asap is driving this,then would it not be simpler to look at TF? With system you’re describing the materials costs are stacking up,never mind the labour. 

Would planning accept brick effect render system? 

Have seen some done in conjunction with EWI & the results were pretty good. 

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1 hour ago, PeterStarck said:

I don't quite follow your calculations but my brick slips weigh 400g each.

 

 

In my calculation I was assuming a full brick 2kg weight which is at the lower end 2kg and hence a per 15mm slip weight of 300g. There is a large margin to such calcs because the basic brick material weigh could be between 2 and 3 kg. Slip thickness are anywhere between 7mm and 20mm.

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15 hours ago, PeterW said:

Unless you buy your own Kwikstage scaffold, you will end up with a lot of additional cost with this approach. Two skins of block and then the slip system means  you will need to either keep the scaffold up over winter (expensive if not owned) or drop it and then have it rebuilt. 

 

 

I was thinking the scaffolding would come down after the roof was on, then later a 24 ft run of Kwikstage would do for the slip cladding.

 

15 hours ago, PeterW said:

Last time I checked, handmade slips were coming in at £1.15-£1.60 each, so basically more expensive than bricks. 

 

 

I am seeing stock prices in the 40p to £1 range, though the better looking examples are at the top end.

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34 minutes ago, Brickie said:

With system you’re describing the materials costs are stacking up,never mind the labour. 

 

 

The driver for Plan-C (slip cladding) is that thin-joint + celcon jumbo blocks looks diy approachable and likewise for slip cladding, this would sidestep the current shortage of brickies and bricks.

 

The 2017 prices in the House Builder's Bible costs thin-joint inner wall at £15 per m2 for material. Fancy heritage bricks are more like £60 m2 plus mortar. I have not found a m2 price for Celcon jumbo's but we could be looking at £7000 (plus cills and lintels and trays) for a diy thin-joint cavity wall masonry structure up to gutter height which is appealing. The joker would be the cost of slip cladding.

 

If was considering a cleansheet design outside a conservation area then thin-joint, jumbo block cavity wall with rendered cladding looks good on paper.

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5 hours ago, epsilonGreedy said:

 

In my calculation I was assuming a full brick 2kg weight which is at the lower end 2kg and hence a per 15mm slip weight of 300g. There is a large margin to such calcs because the basic brick material weigh could be between 2 and 3 kg. Slip thickness are anywhere between 7mm and 20mm.

I see, but most bricks have frogs or holes and most of the slips I looked at were 15mm so I think you'll probably be looking at around 24kg/m2 which would put it much closer to the 29kg limit and that's without the adhesive.

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@epsilonGreedyHaving read a number of your posts I think you should look again at timber frame.  It will mean more likelihood of weathertight by Xmas and you can build the brick skin at your leisure.

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2 hours ago, Mr Punter said:

@epsilonGreedyHaving read a number of your posts I think you should look again at timber frame.  It will mean more likelihood of weathertight by Xmas and you can build the brick skin at your leisure.

 

There's definitely a big advantage is going from foundations to weathertight in a week, it takes loads of uncertainty out of the build and allows firm slots to be booked for first fix trades well in advance, which itself is a significant benefit now that people are getting stretched and so harder to get hold of at short notice.

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We could lock our front door and secure our house on day 9 of the frame erection. The interior was 100% weather tight, so as J says TF can have huge advantages if you get the supply chain aligned.

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7 hours ago, TerryE said:

We could lock our front door and secure our house on day 9 of the frame erection. The interior was 100% weather tight, so as J says TF can have huge advantages if you get the supply chain aligned.

 

 

@JSHarris & @TerryE

 

I am listening, the problem is I have spent 5 months going from zero knowledge of self-build to the point where I can lay in bed at night and picture the construction of a brick & block house. Doing a mental reset on all that and starting a learning curve on all things TF feels like a huge step back.

 

Another poster here is documenting his troubles with a Potton homes contracted TF foundation base, what surprised me was how similar things look at this stage except for "pad stones". At what point in the foundation construction does a build become irrevocably committed to construction method (ignoring passiv slabs in this context).

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1 minute ago, epsilonGreedy said:

At what point in the foundation construction does a build become irrevocably committed to construction method 

 

When you’ve laid the first block. 

 

Most TF (not all) need a wider inner skin so sit on a 140mm block with a 50mm cavity and a 100mm outer skin. This means the sole plate isn’t hanging into the cavity. 

 

Others build up off the ground floor so your GF construction has to be wider all round to leave a smaller cavity - again, it’s down to choice of supplier. 

 

There are a vast number of TF suppliers and an equal number of good and bad stories on here so don’t just take one and think it’s the norm. 

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15 hours ago, PeterStarck said:

I see, but most bricks have frogs or holes and most of the slips I looked at were 15mm so I think you'll probably be looking at around 24kg/m2 which would put it much closer to the 29kg limit and that's without the adhesive.

 

Point taken, there is probably a reason I could not find ready-made examples of cladding an aircrete outer skin in brick slips 5 meters up to gutter height. Your use-case is much more convincing.

 

I am already thinking ahead post my current self build and considering building a smaller rental property. Thin-joint double skinned aircrete in jumbo blocks still feels like a good diy option providing planning are ok with a lightweight rain screen cladding. 

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OK @epsilonGreedy I hope we may have persuaded you to look at timber frame again.  Have you considered whether a passive slab foundation may work on your site?  Better insulation, less muckaway, no deep trenches, no sub floor ventilation and a clean level work area early on.

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ICF, as mentioned by @PeterW above, can be done DIY, and is also quick (not TF quick, but quicker than B&B)

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If you do decide to go with the thin joint system, I’d first urge you to a) do one of those 10 day courses at a private training provider & b) see if you can find a specific course for thin joint system. 

 

If, after doing both of these you feel confident that you can handle it then start considering it for your build. 

 

A 10 day course is no substitute for an apprenticeship but obviously that’s out of the question, but the more hands on tuition you receive the better. 

Youtube videos are a useful resource but nothing compares to learning in the flesh. 

 

As I said, I only did thin joint once, probably 15 years ago now but I’d been on the tools for 5 years by then & had my qualifications, & I still struggled. 

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Thinking a little bit outside the box, if waterproofing is your main priority, why not consider something like (if not necessarily this exactly, roofing felt wrapped around and tacked to the inner leaf for the period. Or there is an american product (i assume there to be a UK equivalent) called line-x which i think is some form of sprayable polyeurathane material - this can also be pulled off again afterwards.

 

OR - And I guess this is the most costly alternative, wrap the scaffolding. Check a company called Rhino, thy have a really decent cost calculator and several case studies on their website. This would allow not only that the building is protected from the elements, but works could continue over the winter period.

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TF comes with breather membrane. Could you not use that as a waterproof covering somehow although it would clearly cost. TF is watertight so quickly I think you'd be mad not to reconsider it if you need to get to watertight and then mothball. We had no issues AT ALL with our TF kit other than a late notice change of delivery by a few days. 

 

Edited by newhome

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We were advised that our timber frame was OK to stand outside without cladding for around 6 months or so.  It came with the wall and roof membrane on, and the latter kept heavy rain out for around 8 weeks whilst our roofer and in-roof PV people worked around some extremely bad weather.

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We were lucky with the weather when the roof sarking and tiling was completed in September straight after the frame was up, but when the outside stone and blockwork was started in October the weather was dire and had to be abandoned many times either because of torrential rain or because it was just too windy for anyone to be working at height. And when I say windy it gets really windy here right by the sea, and the gusts can be enough to take you off your feet at times. So that didn't get finished until December, but at least the fact that we had a timber frame and breather membrane meant that wasn't a huge concern as the house was still watertight and could have remained as was for a while longer if needed. 

 

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