Double concrete block skin?

[Shytalkz]

It's the love that dare not speak its name...

 

[freddiemercurystwin]

Provided stepped dpcs are inserted in the right places (and weep holes TO KEEP BUILDING CONTROL HAPPY) and the ties are installed correctly with just the stone and no blockwork there's no reason to see why water ingress should be an issue, as mentioned by someone else its no different to an outer skin of brick.

 

[gday2uk]

whats the big problem gday , skin of limestone +cavity+ insulation+inner blockwork

As long as there are two skins there should be no problem with damp from outside. Also with a cavity you can obviously insulate it. Can you not get limestone faced blocks to use for the outer skin? I would have thought a purely limestone outer wall would be expensive? Also the porosity will vary depending on the type of limestone used so if a dense un-porous type is used there will also be no problems building it single skin.

As cowboyontheloose likes to say - 'should have gone to specsavers'

 

[freddiemercurystwin]

As soon as I wake up

Every night, every day

I know that its you I need

To take the blues away

It must be love, love, love

It must be love, love, love

Nothing more, nothing less

Love is the best

I think its sweet!

 

[gday2uk]

 

[fastneattrowel]

As soon as I wake up

Every night, every day

I know that its you I need

To take the blues away

It must be love, love, love

It must be love, love, love

Nothing more, nothing less

Love is the best

I think its sweet!

hehe.

 

[fastneattrowel]

I've just got planning permission for my sister-in-law for a two storey rear extension to their house. They're just getting prices from builders and one builder who has been to look at the project has told them that he strongly advises that they build the walls with two adjacent skins of concrete block, then an insulated cavity and then the external skin of limestone. He's told them that as Limestone (the outer skin) is so pourus they'll get damp problems if they don't use a double skin of blockwork.

Firstly, does anyone know if using a double skin of blockwork would help prevent damp?

Has anyone ever built a cavity wall with a double blockwork skin on the inside so prevent damp? yea its true that the stones are uneven and difficult to lay and leaning them against blocks would be easier but nothing to do with damp probs if theres a cavity,id a been honest and said them stones are a pain in the neck so il do a inner skin then cavity then another skin of block work then the stones,kind o guy iam,

Is the builder trying to increase his time he's on site while work is a bit slack?

Most of the work we are involved with is built from either Limestone or Gritstone and as far as i can recall we have only once specified an inner skin of more than 4inch block once when the client specifically wanted thick wall. I personally have never heard of any of our clients having damp problems from single blockwork skin walls, certainly where the walls have not been retaining walls anyway??

yea its true that the stones are uneven and difficult to lay and leaning them against blocks would be easier but nothing to do with damp probs if theres a cavity,id a been honest and said them stones are a pain in the neck so il do a inner skin then cavity then another skin of block work then the stones,kind o guy iam,

 

[AndrewSchofield]

I've just got planning permission for my sister-in-law for a two storey rear extension to their house. They're just getting prices from builders and one builder who has been to look at the project has told them that he strongly advises that they build the walls with two adjacent skins of concrete block, then an insulated cavity and then the external skin of limestone. He's told them that as Limestone (the outer skin) is so pourus they'll get damp problems if they don't use a double skin of blockwork.

Firstly, does anyone know if using a double skin of blockwork would help prevent damp?

Has anyone ever built a cavity wall with a double blockwork skin on the inside so prevent damp?

Is the builder trying to increase his time he's on site while work is a bit slack?

Most of the work we are involved with is built from either Limestone or Gritstone and as far as i can recall we have only once specified an inner skin of more than 4inch block once when the client specifically wanted thick wall. I personally have never heard of any of our clients having damp problems from single blockwork skin walls, certainly where the walls have not been retaining walls anyway??

yea its true that the stones are uneven and difficult to lay and leaning them against blocks would be easier but nothing to do with damp probs if theres a cavity,id a been honest and said them stones are a pain in the neck so il do a inner skin then cavity then another skin of block work then the stones,kind o guy iam,

Thanks FNT (hope you don't mind the abbreviation!) i've advised them that I think he's wrong telling them they WILL have damp problems if they don't use the second skin of blockwork and that if they don't use him and other builders are happy to build without the second blockwork skin then there's no need to do so. I think they're wasting time, money and even floor space to accommodate the personal preference of one builder out of the many they've spoken to.

 

[AndrewSchofield]

I've now spoken to the S-I-L and partner and they're still adamant that they want to go with the two skins of concrete block and the outer skin clad with Limestone - apparently the builder told them that building with irrgular shaped pieces of limestone makes it very easy to drop mortar down the cavity and end up with cavity bridging problems so that where he was coming from as suspected by the folks on this forum. The question now is - to save space on what is going to be a fairly thick wall by modern day standards, can they construct the blockwork skins out of 75mm blocks instead of standard 100mm blocks?

 

[fastneattrowel]

yes andrew 75mm block a be fine , i know where there coming from its very hard to lay and balance the stones ,should find a merchant on line who supplys 75mm thermos,good luck

 

[legs-akimbo]

I've just got planning permission for my sister-in-law for a two storey rear extension to their house. They're just getting prices from builders and one builder who has been to look at the project has told them that he strongly advises that they build the walls with two adjacent skins of concrete block, then an insulated cavity and then the external skin of limestone. He's told them that as Limestone (the outer skin) is so pourus they'll get damp problems if they don't use a double skin of blockwork.

Firstly, does anyone know if using a double skin of blockwork would help prevent damp?

Has anyone ever built a cavity wall with a double blockwork skin on the inside so prevent damp



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]

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.

 

[legs-akimbo]

yes andrew 75mm block a be fine , i know where there coming from its very hard to lay and balance the stones ,should find a merchant on line who supplys 75mm thermos,good luck

Balancing the blocks....what absolute tosh, have you ever seen a good stone mason at work ? they dont use a bricklaying consistancy mortar.

 

[AndrewSchofield]

I agree with you legs - but they don't believe me over this guy (they aren't even using this guy for the build because he's too busy - but taking his advice anyway!) nothing i can do to change their minds!!

 

[freddiemercurystwin]

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.