Building a garage

[Vinnykaka]

Hi There all,

I am in the process of building a garage/room at the back of my garden. It will be built using concrete breeze blocks 440x215x100mm and the approx dimensions are LxWxH 3m(10ft) x 9m(30ft) x 2m (7ft)

There is an old wooden shed which is coming down and the floor has slabs at the moment.

Is it better to build the walls first and then lay the concrete floor or shall i lay the concrete floor first?

When digging foundations for the walls , will 3ft be enough or shall i go deeper

when laying the floor i have been advised to have the
subfloor 150mm deep
sandblind 50mm
DPM 1000 gauge
concrete 100m

there is a large area and i was enquiring if it is better to buy in ready mix or shall i mix myself? if so what mixture would you recommend?

Any help will be appreciated as this is the first of my projects.

 

[noseall]

Is it better to build the walls first and then lay the concrete floor or shall i lay the concrete floor first?

Build the walls up to dpc then lay the floor slab.

When digging foundations for the walls , will 3ft be enough or shall i go deeper

1 metre dig is regarded as the accepted norm, though ground conditions will ultimately decide.

when laying the floor i have been advised to have the
Sub-floor 150mm deep
sandblind 50mm
DPM 1000 gauge
concrete 100m

sub-floor could be as little as 100mm thick and the sand blinding need only be as thick as to be effective, i.e. if the stone compacts evenly 25mm may be ok.

there is a large area and i was enquiring if it is better to buy in ready mix or shall i mix myself? if so what mixture would you recommend?

Using ready-mixed concrete is all about logistics. If it can be shot straight into the trench and you can keep your order to full wagon loads then it can be efficient and inexpensive.

If on the other hand you need a pump, or it needs barrowing over long distances, or there are drainage hindrances or excessive level changes and lots of shuttering, then mixing it yourself may be better.

 

[Vinnykaka]

Thanks a lot noseall for all the info, gratefully appreciated!!!!!

just one thing, when you mentioned build the walls upto dpc what is dpc and what is involved? e.g concrete upto ground level or half concrete half engineering brick?

I will also take your advice of mixing the concrete myself for the floor as opposed to readymix because the garage is a long way from the road (80ft) and i will require a wheelbarrow or pump. I have been told to mix 3 ballast to 1 part cement, does that work for you?

Kind Regards

Vin

 

[^woody^]

Check out local concrete companies, as some may operate wagons that mix the concrete on the back, in the exact quantities you want, and then a few of their guys barrow the concrete to where you want it.

This can work out cheaper than a traditional supplier, and pump, or with you barrowing

 

[stuart45]

3 and 1 is a bit on the strong side. 6 and 1 is the usual mix.

 

[wavetrain]

6 and 1 is the usual mix.

6:1 for a concrete floor? 4:1 surely?

 

[Vinnykaka]

will that be the same for the foundation of 1m for the walls?

Thanks guys, your help is greatly appreciated.

 

[wavetrain]

foundations 5:1

 

[stuart45]

The correct mix is 6 and 1.

 

[wavetrain]

The correct mix is 6 and 1.

For a floor, are you sure?

 

[noseall]

just one thing, when you mentioned build the walls upto dpc what is dpc and what is involved?

Damp proof course.
You would normally lap the dpm (damp proof membrane) up onto the dpc. Garages fair slightly different to normal dwelling scenarios as the floor of the garage corresponds with external floor levels for obvious reasons. However, the dpc still needs to be 150mm higher than external ground level. This would mean showing a visible strip of membrane, so we don't bother lapping as it would only get damaged anyhow.

I will also take your advice of mixing the concrete myself for the floor as opposed to readymix because the garage is a long way from the road (80ft) and i will require a wheelbarrow or pump. I have been told to mix 3 ballast to 1 part cement, does that work for you?

Six parts ballast to one cement.

 

[stuart45]

The correct mix is 6 and 1.

For a floor, are you sure?

I am sure that this is the mix for a concrete floor slab. 3/1 or 4/1 would be used for the floor screed.
Ballast needs less cement than sand as the larger parts of the ballast (up to 20mm) need less cement binder to cover them than sand particles.
The old mix used to be 1/3/6 cement/fine/coarse.

 

[foxhole]

I would use 265mm blocks as it avoids the need for piers and will make the garage/room warmer and drier.

 

[wavetrain]

The correct mix is 6 and 1.

For a floor, are you sure?

I am sure that this is the mix for a concrete floor slab. 3/1 or 4/1 would be used for the floor screed.
Ballast needs less cement than sand as the larger parts of the ballast (up to 20mm) need less cement binder to cover them than sand particles.
The old mix used to be 1/3/6 cement/fine/coarse.

TY for that, so that is where I ahave been going wrong...mind you my 4:1 was for an outside drive.

But not all all in one ballasts are created equal. I'm not naming names here..but sift them and in some its more like 6/3 fine/coarse!