Double concrete block skin?

[stuart45]

Andrew,
If you use a full fill insulation, even a more random stone wall can be built without a backing wall.

 

[fastneattrowel]

Another point.....If building with a porous stone on the facade how can damp possibly be an issue, this type of stone allows moisture to dissipate naturally, if there are any concerns about moisture being trapped within the stone of a pourous material then this is readily overcome by building in a traditional method replacing ordinary portland cements with traditional lime mixtures that also accomodate naturally the dissipation of moisture, though this is another argument again.

hey lugs keep to what you know best and it certainly isnt laying bricks or stones ,aircrafts id say with them ears

 

[AndrewSchofield]

Andrew,
If you use a full fill insulation, even a more random stone wall can be built without a backing wall.

Cheers Stuart - that makes a lot of sense! I still don't think i'll be able to talk em round though. They're farmers and i though the extra cost of blocks, mortar, labour, bigger foundations would swing it but no?? Usually the mention of saving a few quid is the deal sealer with farmers!!

 

[freddiemercurystwin]

They're farmers and i though the extra cost of blocks, mortar, labour, bigger foundations would swing it but no?? Usually the mention of saving a few quid is the deal sealer with farmers!!

Water penetration is undoubtedly the most common problem with buildings new and old, the cost and hassle of putting one problem with damp right in the future is often under estimated. With respect to ending up with a thicker wall, whoever did the planning drawings should have allowed for thicker walls. Opinion on the need for a block outer skin is divided, nevertheless you seem to be taking the advice that suits you.

 

[AndrewSchofield]

With respect to ending up with a thicker wall, whoever did the planning drawings should have allowed for thicker walls. Opinion on the need for a block outer skin is divided, nevertheless you seem to be taking the advice that suits you.

I did the planning drawings - why should i have allowed for thicker walls??

I've never detailed a job with a blockwork cavity wall faced with Limestone before and indeed, no-one at the practice i work at has in nearly 30years of detailing drawings, and never have we heard of any of our clients or builders having had problems occur with damp penetration. Indeed, my S-I-L has spoken to a number of builders and only one of them has advised them of the need for the extra skin of block. It would appear to me that this is this particular builder's preference of how to build, rather than an essential feature in the construction of Limestone cavity walls, and the majority of posts on here seem to back that up.

I'm not bothered if they have two skins of blockwork or not - they're paying for it, not me. I do, however, want to make sure they are properly advised as to whether it is necessary or just a preference of a builder that isn't going to be building the extension anyway.

 

[fastneattrowel]

well said freddy

 

[freddiemercurystwin]

I did the planning drawings - why should i have allowed for thicker walls??

I've never detailed a job with a blockwork cavity wall faced with Limestone before and indeed, no-one at the practice i work at has in nearly 30years of detailing drawings

Wait a minute, you've been detailing stuff up for 30 years and you resort to a forum for backup! I just thought you were a Fred Bloggs doing a favour for someone. I hope your clients know they're getting such a service!

 

[AndrewSchofield]

I did the planning drawings - why should i have allowed for thicker walls??

I've never detailed a job with a blockwork cavity wall faced with Limestone before and indeed, no-one at the practice i work at has in nearly 30years of detailing drawings

Wait a minute, you've been detailing stuff up for 30 years and you resort to a forum for backup! I just thought you were a Fred Bloggs doing a favour for someone. I hope your clients know they're getting such a service!

I didn't say i've been here 30years (for one thing i'm not even 30years old). I don't get involved with detailed drawings all that often, my main job is to dealing with planning issues but I'm doing a private job for my sister-in-law and one of the builders has suggested something that i've never heard of, so i asked the guys in the office (which has been running for nearly 30years) and they'd never heard of it either so i posted the question on the forum to see if anyone has ever heard of it or if the builder is really talking out of his rear end - is that unreasonable? It seems a few have heard of wall construction with the method he describes but most concur with our office practice that it isn't necessary.

You still haven't explained why you feel the planning drawings should have allowed for thicker walls?

 

[fastneattrowel]

At the end of the day andrew you been given advice on how it could be done and you keep going back to the way you want it,if it was my house id do it the easiest way ,ie a stone 75mm block cavity 100mm block,freds spot on with his answers,i think you should go back to the drawing room and think again

 

[AndrewSchofield]

i think you should go back to the drawing room and think again

Great advice that - cheers.

I think you should go back to the start and read again. I have never asked for advice on how it could be done, i asked if building a cavity wall with blockwork inner skin and limestone outer skin is wrong and would lead to damp problems as i've been told this it is the case, but my experience (albeit somewhat limited) and that of others i work with is that this is not true. I now understsand that some people prefer to detail and/or build stone walls with a inner and outer skin of block and others don't bother with the outer skin of block but ultimately that the outer skin of block is not absolutely essential to prevent damp penetration. Furthermore, i have never suggested FMT's comments were inaccurate - conversely i believe he has responded to some of my other posts on this site and i believe his comments to be very valuable.

You seem to be suggesting i'm wrong, and yet the method you would use yourself is what i would suggest also!?!

 

[freddiemercurystwin]

It seems a few have heard of wall construction with the method he describes but most concur with our office practice that it isn't necessary.

But you said no one in your office has direct experience of stone clad walls!

i posted the question on the forum to see if anyone has ever heard of it or if the builder is really talking out of his rear end

Frankly, I think I’d be doing a disservice to my clients, private or commercial, if they knew I’d taken advice from an Internet DIY Forum and not spoken directly with experts in the trade.

You still haven't explained why you feel the planning drawings should have allowed for thicker walls?

It’s the sign of a good planning application that takes account of the build method as well as the rest of the regs etc. It shows lack of forethought.

in the office (which has been running for nearly 30years)

Your practice website says 15 years BTW.

 

[legs-akimbo]

The builder you are dealing with is talking absolute and utter complete nonsense. I can assure you 100 % that the method of construction is complete overkill. In all my time I have never seen anything other than a regular two leaf cavity block construction( unless specifically specified for other reasons than damp)with expanded metal left between the horizontal bed joints at intervals to accomodate the stone external facade which is constructed with stone bedded onto a semi dry sharp sand mix, so no difficulty of lay.
No other detail other than a spread (wider) footing is required Irish housing stock is predominantly block built and most have stone frontage.
If you want a definitive answer contact Roadstone the main supplier of block to the Irish market at www.roadstone.ie. I have folders full of drawings in my office from over the years and not one of them would specify in the detail of schedule of works anything other than standard 4" cavity construction, sack this builder before he even starts, he doesnt know his a**e from his elbow.

legs-akimbo, as I understand it, the builder wants to do a traditional block cavity wall with 1 skin of block for the inner and outer leaves and face the outer skin with the stone. Experience of other contributers to the thread is contrary to your opinion. Your reference to www.roadstone.ie. appears to be a cast block manufacturer not a natural stone supplier, they are 2 different animals. There is no problem building with skins of 75mm provided it works out structurally and thermally. As with any cavity wall with respect to the cavity width, to keep building control happy, you need to pay atention to Part C regarding how exposed (or not) the site is.

Freddie you are quite correct, I misread the original post and assumed there were two internal skins and one outer with a stone facade.
My post above concurs with the detail specified by the builder in question, a 100mm block cavity wall construction, so in essence Andrew the builder is absolutely correct.
Building a single leaf stone clad internally insulated wall would indeed lead to problems with damp as this would lead to Interstitial condensation on the internal wall.
A well built cavity wall of block that is of course continuously seperated from the external, will harness the cavity to isolate moisture content gained from external conditions from moisture gained from the room. Both leafs then have the potential to dry out towards the cavity or their other face.
Single skin construction of all manner, and the proposed block/ stone non cavity is in effect single skin..... will have an inadequate U value without being internally insulated.
An internally insulated single leaf construction has the room face heated to within a few degrees of room temperature as it is warmed by the radiant heat of for example a fire. This means that the the point where vapour condenses (The Dew Point) is often at the face of the wall according to atmospheric conditions....condensed vapour in simple terms is damp.
Single leaf construction with internal insulation has to be given specific considerations to negate the possibillity of interstitial condensation other than just whacking up a timber rockwool filled stud or thermal liner board.
I mention this because the primary consideration for this construction should be the U value of the walls and I work this out to be around 3. on your preference if non insulated.
whereby the cavity proposed build would be around 0.32 which is a huge difference.
These are the kind of things I would have thought you would have learnt Andrew or most certainly would be second nature to your colleagues in the office.

 

[fastneattrowel]

Andrew those guys must know its much easier to lay the stones against a back up wall,when they said its might cause damp problems if they dont there could be a little bit of truth in that , the cavity is easier to clean with a flush backing and you dont want any muck anywhere near the insulation
,how much more expensive was it doing the extra block work?

 

[fastneattrowel]

The builder you are dealing with is talking absolute and utter complete nonsense. I can assure you 100 % that the method of construction is complete overkill. In all my time I have never seen anything other than a regular two leaf cavity block construction( unless specifically specified for other reasons than damp)with expanded metal left between the horizontal bed joints at intervals to accomodate the stone external facade which is constructed with stone bedded onto a semi dry sharp sand mix, so no difficulty of lay.
No other detail other than a spread (wider) footing is required Irish housing stock is predominantly block built and most have stone frontage.
If you want a definitive answer contact Roadstone the main supplier of block to the Irish market at www.roadstone.ie. I have folders full of drawings in my office from over the years and not one of them would specify in the detail of schedule of works anything other than standard 4" cavity construction, sack this builder before he even starts, he doesnt know his a**e from his elbow.

legs-akimbo, as I understand it, the builder wants to do a traditional block cavity wall with 1 skin of block for the inner and outer leaves and face the outer skin with the stone. Experience of other contributers to the thread is contrary to your opinion. Your reference to www.roadstone.ie. appears to be a cast block manufacturer not a natural stone supplier, they are 2 different animals. There is no problem building with skins of 75mm provided it works out structurally and thermally. As with any cavity wall with respect to the cavity width, to keep building control happy, you need to pay atention to Part C regarding how exposed (or not) the site is.

Freddie you are quite correct, I misread the original post and assumed there were two internal skins and one outer with a stone facade.
My post above concurs with the detail specified by the builder in question, a 100mm block cavity wall construction, so in essence Andrew the builder is absolutely correct.
Building a single leaf stone clad internally insulated wall would indeed lead to problems with damp as this would lead to Interstitial condensation on the internal wall.
A well built cavity wall of block that is of course continuously seperated from the external, will harness the cavity to isolate moisture content gained from external conditions from moisture gained from the room. Both leafs then have the potential to dry out towards the cavity or their other face.
Single skin construction of all manner, and the proposed block/ stone non cavity is in effect single skin..... will have an inadequate U value without being internally insulated.
An internally insulated single leaf construction has the room face heated to within a few degrees of room temperature as it is warmed by the radiant heat of for example a fire. This means that the the point where vapour condenses (The Dew Point) is often at the face of the wall according to atmospheric conditions....condensed vapour in simple terms is damp.
Single leaf construction with internal insulation has to be given specific considerations to negate the possibillity of interstitial condensation other than just whacking up a timber rockwool filled stud or thermal liner board.
I mention this because the primary consideration for this construction should be the U value of the walls and I work this out to be around 3. on your preference if non insulated.
whereby the cavity proposed build would be around 0.32 which is a huge difference.
These are the kind of things I would have thought you would have learnt Andrew or most certainly would be second nature to your colleagues in the office.

what does lugs know, f... all

 

[legs-akimbo]