Building a Garage

[pippo]

Hello,

I am looking into my options for building a new garage to replace a rotten timber garage. I would like to build it out of blocks myself and i have a few questions while I weigh up my options.

The garage is to be 5.2mx3.2m and 2.5m high to the eaves and single leaf to give more internal space. The roof will probably be lightweight using homemade trusses and pvc corrugated sheets. I will get the outside pebbledashed the same as the house.

1) Are dense concrete blocks suitable for this (ie frost attack, weight etc)?

2) Would the walls be damp proof from the rain etc or will it require lining or tanking on the inside?

3) Would it require piers and if so how many/where?

4) Should it have a dpc in the wall?

Thanks in advance for any answers.

Pippo

 

[noseall]

1) Are dense concrete blocks suitable for this (ie frost attack, weight etc)?

Dense 7n conkers will be fine.

2) Would the walls be damp proof from the rain etc or will it require lining or tanking on the inside?

If you intend rendering this structure then driven rain will not be a problem. If not, just make sure the pointing is good and give it a yearly coat of Thomson's water seal.

3) Would it require piers and if so how many/where?

One 450 x225mm pier mid span.

) Should it have a dpc in the wall?

Yes. The dpc should be set at 150mm above external floor level

p.s. what do you mean by home made trusses?

 

[Shytalkz]

p.s. what do you mean by home made trusses?

View media item 9285

 

[pippo]

LOL ^^^

I meant the rafter thingys.

However I will be sporting a lovely pair of those while I try to build it.

I take it 7n is a density rating? Would these bad boys be good enough:

http://www.wickes.co.uk/Dense-Blocks/Dense-Concrete-Blocks/invt/154028

they also do medium density and aerated.

And, how wide and deep do the footings need to be for these walls?

Thanks for the help so far.

Pippo

 

[noseall]

The blocks look ok.

The footings should be 300mm wider than the wall, i.e. 150mm projection each side. so a 100mm wide wall will require 400mm wide footings. These should be laid on good virgin substrate. Building control suggest a minimum of 1m below ground level., though this is a guideline. If the soil is still not firm virgin ground then go deeper.

 

[noseall]

p.s. what do you mean by home made trusses?

View media item 9285

I hope those medicinal pants don't affect the stitches Shy.

 

[Shytalkz]

Actually, I could do with a pair of those at the mo! As it is, I've got two pairs of grollies on and a bag of frozen peas sandwiched between them...!

 

[pippo]

The blocks look ok.

The footings should be 300mm wider than the wall, i.e. 150mm projection each side. so a 100mm wide wall will require 400mm wide footings. These should be laid on good virgin substrate. Building control suggest a minimum of 1m below ground level., though this is a guideline. If the soil is still not firm virgin ground then go deeper.

Thats great, thanks noseall. So if the soil is good at 1m would it be trench fill to ground level or is it partial fill to a certain level below ground with blocks on top?

Pippo

 

[Shytalkz]

If you're in sands, 600-750 depth of footing will be more than adequate.

 

[noseall]

Thats great, thanks noseall. So if the soil is good at 1m would it be trench fill to ground level or is it partial fill to a certain level below ground with blocks on top?

Knock a peg in the ground at what you will assume to be dpc level, usually the same as the main dwelling. This peg is your datum. We would then allow for six courses of (metric) bricks below this datum to the top of the foundation concrete. This translates to two courses of block and measures 450mm or about 18".

 

[pippo]

Thats great, thanks noseall. So if the soil is good at 1m would it be trench fill to ground level or is it partial fill to a certain level below ground with blocks on top?

Knock a peg in the ground at what you will assume to be dpc level, usually the same as the main dwelling. This peg is your datum. We would then allow for six courses of (metric) bricks below this datum to the top of the foundation concrete. This translates to two courses of block and measures 450mm or about 18".

The dpc on the house is indeed around the 150 mark above ground level. so 2 courses of blocks below this at 450 would start 300 below ground level. So I'm looking at 700mm depth 400mm wide concrete foundations.

2 more questions

1) Will the foundations need widened 150 each side around the piers?

2) Does the dpm from the corcrete floor that i intend to lay have to overlap the dpc ? if it does i take it i will need to have my concrete floor 150 above ground level with a ramp up which will lower my interior height. i was hoping to have the floor at ground level.

 

[Shytalkz]

1 For strip footings you should do, for trench fill you don't need to, will it fall down if you don't - no.

2 It's a garage, you don't need a slab dpm but if you want one, then paint the inside face of the brickwork with synth or RIW, something of that ilk, from dpc level down to bottom of slab level, turn ploy dpm up on the painted dpm for the depth of the slab and that'll be more than fine.

 

[hotrod]

Hi pippo,

Is this new garage going to be attached to the main dwelling. I.e. is there going to be a door leading from the garage to the house

 

[pippo]

Hi pippo,

Is this new garage going to be attached to the main dwelling. I.e. is there going to be a door leading from the garage to the house

Hi hotrod

No, its a detached garage and will be 5m from the house so it is classed as an outbuilding. I would like to build it nearer the house but I think it is then classed as an extension which will probably cause more complications.

 

[pippo]

1 For strip footings you should do, for trench fill you don't need to, will it fall down if you don't - no.

2 It's a garage, you don't need a slab dpm but if you want one, then paint the inside face of the brickwork with synth or RIW, something of that ilk, from dpc level down to bottom of slab level, turn ploy dpm up on the painted dpm for the depth of the slab and that'll be more than fine.

Superb thanks Shytalkz