Garage - Do you use 4" solid or 9" cavity

yop

Folks
Would really appreciate your advice.

I am building a garage with an office space at the back.

I was going to build it with 4" solid blocks and 50mm cavity but the lad who is doing up the plans said I should do it with 9" cavity blocks to keep the cost down.

From experience the 9" cavity are not ideal as they seem to leave damp walls.

Whats the opinions please.

AckwelFoley

If you plan on having an office use 4" solids with a 4" cavity. Therefore you can use 50mm insulation.

The other option and the cheaper one is go with the cavity blocks and dryline the office space with insulation

yop

thanks for that. Ya I was thinking that way.

Wondering though say it takes 1200 9" cavity. That would be 2400 for 4".
So extra costs would be the blocks and the price to build them.
If it costs more and I can insulate the office big time, I don't mind that.

AckwelFoley

well its not exactly double the cost.

9" cavities are double the price of 4" 90cent as opposed to maybe 45 cent. but the cost of laying them is the same.

As for the dampness issue, meah, if the shed is plastered well and has 2 good coats of plaster, it shouldnt be an issue, and then with the drylining, there will be no issue.

That said, i wouldnt do it for a house.

slimjimmc

Personally I'd go for the 4"" cavity wall, at least you'll have a solid block interior to hang any fixings off without worrying about finding where the battens are.

gman2k

snyper wrote: »

That said, i wouldnt do it for a house.

There's many a house in Ireland built that way!

AckwelFoley

gman2k wrote: »

There's many a house in Ireland built that way!

there are, but i dont like them.

yop

Wouldn't have them near a house.

I didn't realize that 9" cavity blocks were double the actual cost of a 4" solid.

So really you are talking the extra cost of labour to lay.

9" costs: 1200 * .90 = 1080
Labour (.70 per block) = 840
TOTAL = 1920

4" costs: 2400 * .45 = 1080
Labour (.70 per block) = 1680
TOTAL = 2760

So you are probably talking the guts of 1k euro.

Carlow52

yop wrote: »

Wouldn't have them near a house.

I didn't realize that 9" cavity blocks were double the actual cost of a 4" solid.

So really you are talking the extra cost of labour to lay.

9" costs: 1200 * .90 = 1080
Labour (.70 per block) = 840
TOTAL = 1920

4" costs: 2400 * .45 = 1080
Labour (.70 per block) = 1680
TOTAL = 2760

So you are probably talking the guts of 1k euro.

Plus the cost of ties and insulation fitting in the cavity which is a PITA as opposed to either internal dry lining or EWI.

If going 9" cavity try make it so as you buy 1/2 a 9" block which are called footballs so as there is no cutting on the 9" hollow when u get to the end of a course.
what usually happens is that they are Guntered in 1/2, leaving a mess.

If building a cavity I would fill it with beads

Spread

Personally I'd use 9" cavity, battened out with 2"X1", cables dropped in, insulation board fixed and skimmed. Waterproofing added to the outside render. This will give you a warm room.

yop

Waterproofing? How do you do that?

Spread

yop wrote: »

Waterproofing? How do you do that?

You add the appropriate amount of a waterproof chemical to the sand/cement. Instructions (on container) should be adhered to as too much is as bad as too little.

Carlow52

12 posts and its not built yet: long weekend and pubs shut Friday:D

I don't know exactly what you have in mind here but perhaps you might consider the following:

I assume the garage is just a garage so the spec is not as high as the office.

well laid blocks and good render will make it weather tight: I emphasize the need for good block laying: if garage only I would consider 4" on flat: very quick and easy to do right.

For the office, consider a stand alone internal structure, away from the exterior walls, made from 4" stud walls, suitably insulated: just insulate the concrete floor or else have raised floor in the office.

IOMO it would simplify the matter: window can be incorporated with a bit of thought

yop

Thanks for that.
The shed is of 2 parts so to speak. The garage is an 18*18 garage, for tools, lawnmower etc.
Then behind that is the office, a 12*18 area with 2 windows and a door into it from outside.

That could be the idea with regard the walls as I will have to heat it with a gas/electric heater. I can insulated it well then.

Thanks

Carlow52

okay, given that it an office I would insulate as per the yellow in the attachment: say 75-100mm on insulated board and use wall mounted cable ducting such shown here
http://www.mkelectric.com/en-GB/Products/CM/PD/Prestige%203Ddadoandskirting/Pages/default.aspx

for all services:
no chasing walls
no chopping insulation/board etc
airtightness maintained
flexible re redesigning interior

there are 2 types of insulated board: one needs battens, the other goes on the wall: let the experts here suggest the better one.

floor and ceiling will need insulating also

if pvc windows get the extra 30mm slips added on to allow a decent amt of insulation on the inner reveals and the head

yop

Excellent idea. Its important to keep it airtight for the heat I am sure. I will put 4" of insulation in the floor and the same in the ceiling space.

Thanks V much.

Have a much better idea of where I should be going with this.

Stove Fan

We have just built a large garage. We opted for 4 inch blocks laid standard front and back and 4 inch block laid flat for the gable wall. Our garage adjoins the house gable.
Now that I have slated the roof it's very dry, Just waiting to get it plastered.

Our house that I have now fully renovated is very, very dry and it's block on the flat. It has been empty for 30 years. I would have no problems buying a house with solid block walls. I have slabbed them internally using kingspan, makes it nice and warm:D

Stove Fan

paddy147

May I suggest (while you are building the garage/office) running ducting down from the house to the garage for your power cable,alarm cables,co-ax cable and cat5 or cat6 cables in the ducting aswell.:)

A garage requires an IP rated fuseboard and also use SWA.
3 core 10 square SWA will cover everthing and also for future proofing too.

Pre-install fish wires into the ducting and then tape on a new fish wire as you pull your existing fish wire and cables down the ducting.

Makes life so much more simple and easy in the future if you ever want to install more cables.;)

paddy147

Just to add to this.

Several underground ductings comming up into the garage,containing various cables,like SWA,alarm cables,cat5e and co-ax cables.

yop

Thanks Paddy, good advice that.

Only problem is getting the cables from the house into the ducting, I have the paths in already.

Any suggestions?