Strawbale render.

[satamax]

Hi everybody.

Well, son far, i have this.



I want to do a lime and sand render. A friend is supposed to get his turkish employees to do it with the pump. But he insists that i should put a thiner mesh, instead of the rebar slab reinforcin grid i have been using. I thought the strawbales were rough enough for the render to adhere. What do you think? Carry on this path? Or do a nite and lime plaster? Nite is schistic clay and sand mixture, that you find in the bottom of glaciary lakes. Thanks everybody.

[Jura]

I'd say  we hardly ever apply any mesh on strawbales. (Except  burlap on difficult surfaces)
But I'm mostly in post and beam construction.
Bale are laid flat and fine cut  ( one can see the stalks cross section)and such created  enormous adsorption area makes clay penetrate it prety deep.


Btw. Arent U  afraid of using metal ? (due to possibility of moisture condensation -I mean)

[satamax]

Thanks jura.

What do you mean by moisture condensation? It will be covered by a 2" layer of lime plaster.

[Jura]

Clay and lime  plaster are vapour permeable.

Depending on  strenght of factors driving the diffusion process of moisture (temp difference, % of humidity inside and outside)(water vapour being transported either direction) the vapour particle  encountering colder metal on its way condensates and that's sth we try to avoid by all means.

Dew point. inspectapedia.com/Energy/Dew_Point_Calculation.php

I can see the building doesnt have overhangs protecting it from direct driving rain, therfore the water intake can be pretty siginficant.
Depending on the speed of drying the amount of water absorbed may not have enough time to evaporate. Whch can be harmfull to the  strawbales.
Fungi do not need that much moisture to thrive.
And if there is  water in a liquid form anywhere close to the  bales  - roting is almost guaranted.

That's why we  try to spray a first base slip  as deep into  straw as possible.
(Tom Rijven prefers even pouring clay slip onto both bales surfaces b e f o r e they are put into the wall - much heavier to do but slip penetrates it  really deep resulting in a reasonable  protection)
The layer of  clay lime slip covers the  straw protecting it  from a direct contact with water and allowes cappilary proces of driving the moisture out.


But  If it is the place I conclude from your signature  I'd be carefull. We need to remember this building technique was born under  dry sky of Nebraska. And there is no bigger straw enemy than water.  

Were I you I'd also  protect the building base against splashing  water at the base. We try not to have bales lower  than 50 cm from the ground.

Is there any capilary break between the bricks and the first layer of bales ?

Here is an article on the subject in proper english
thelaststraw.org/bonus-articles/moisture-and-straw-bale-walls/

[satamax]

Hi Jura.

Thanks for the reply. Ridge overhangs will be increased in the future. I will also protect the top of the strawbales bellow the wood paneling with some roofing steel. So, i could ventilate there. i haven't put a vapour barrier between bricks and Balles. Behind the bricks, it's ventilated. About 15x27 cm gap. So ventilated at the the bottom top. I could even do a natural draft inducer.

Thanks again.

Max.

[Jura]

Mar 14, 2017 0:47:13 GMT -8 satamax said:

Hi Jura.

Thanks for the reply. Ridge overhangs will be increased in the future. I will also protect the top of the straw bales bellow the wood paneling with some roofing steel. So, i could ventilate there. i haven't put a vapour barrier between bricks and Balles. Behind the bricks, it's ventilated. About 15x27 cm gap. So ventilated at the the bottom top. I could even do a natural draft inducer.

Thanks again.

Max.

Max! I'm not sure whether I got U properly.
Are the strawbales just an outside insulation layer, covering a standard brick building??
I thought it was a load bearing building.

No any barriers while using strawbales,please!

What I meant was not a vapour barrier, but applying a capilary break material (bituminous paper for example)between a rised wall base and first layer of strawbales.

btw. What was your decision about using the metal mesh after all?

[satamax]

Hi Jura.

Thanks a lot for the help.

Well, the strawbales are just an insulation layer against an optibric wall. (hollow bricks) These are by no means load bearing.

I used a metal grid, because a masson friend (40 employees, he's the boss) told me that would be a good idea. Me, i had no idea whatsoever, on which way to hold these. I

I understans the capilary break under the bales. And i didn't do it. But the bricks under, are just laid on the ground. And it's hollow bricks again.

So it's all ventilated underneath.

[Jura]

Mar 24, 2017 5:23:57 GMT -8 satamax said:

Hi Jura.

Thanks a lot for the help.

Well, the strawbales are just an insulation layer against an optibric wall. (hollow bricks) These are by no means load bearing.

I used a metal grid, because a masson friend (40 employees, he's the boss) told me that would be a good idea. Me, i had no idea whatsoever, on which way to hold these. I

I understans the capilary break under the bales. And i didn't do it. But the bricks under, are just laid on the ground. And it's hollow bricks again.

So it's all ventilated underneath.

thanks very much!

will U have any space to see & keep an eye on what is going on to the strawbales that touch the wall base?

when (if ) rotting starts U will smell it

I saw an building in which all walls got rotten due to not using capillary break.
I could hardly believe it was wet up to 1 m as if u took the ballots out from water.

As to trusting your friend.. not many ppl I met who had enough experience with building with strawbales and didn't commit mistakes using well tried and tested methods of "standard construction".

any photo of the cross section of the space where the ballots touches the brick wall?

[satamax]

[Jura]

Tahnks for placing the photo.

ugh!

Fungi are like humans. (in fact we used to be one spiece a couple of mln years ago)

They need moderate temp and oxygen and moisture to thrive.

I'm afraid the lower bales provide perfect conditions for them to do so.

The fact the bricks are perforated does not change much I'm afraid.

Monitor it often.
As well as the places where the bales touch the brick wall.

The wall will always be colder thus allowing the vapour to condensate and form a drop which will then be capillary sucked in by the straw.

Then if there is much of it & driving force (low humidity outside and higher temp inside) is not strong enough to direct it outward (toward the plaster) the water will remain in the bales and... soon our fungi brothers will appear.