Raising the Garage Roof

[That Bloke]

Timber garage 6 mtr x 6 mtr by 2.4mtrs high. The apex is 1.0 mtrs high over the basic box. There are considerable underbuildings and a 4in floor slab between the 6in block under building.

I want to fit a two post car lift and rather than the present 2.4mts headroom it should be nearer 3.5 mtrs. Talked to the garage supplier and he said jack up the garage and build a 1.2 mtr breezeblock wall then bolt the garage down on to that.

He said they have a structural engineers certificate for the 2.4 mtr timber box height and do not want to get into going above that height.

So prior to getting a structural engineer to do the calcs what are the panels thoughts.

My thoughts are.

If I put in a 1.2 mtr high timber sections using the same 100 x 45 members between the roof and the top of the existing box.

The extra weight of the garage is not significant to the under buildings.

If the roof has a heavy snow load that would put a more stress on the new section / old section interface and down at the joint to the underbuildings.

The main problem would be the bending effect at the ground on a high wind day as the wind load is higher due to the extra sail area and the extra load is at a higher levering point.

I know that I need planning permission if I go above 4.0mtr and I would be about 4.5mtr.

Has anyone do such a project!

[That Bloke]

My neighbour has a pit which I have access to. I want a lift as it is useful for lots of other jobs on cars. Next time you look in a modern car repair shop, how many of them use a pit!

[Dave Osborne]

Commercially, you can buy a lift and have it installed and signed off for much less than the labour/materials cost of digging a pit, installing monitoring equipment and explosion-proof lighting and having barriers and covers. Consequently, pits are not only relatively expensive, but deprecated by HSE (unless you're talking HGV workshops, where the practicalities (and cost/benefits) are different and pits quite common).

Lifts may be more versatile than pits, but that's not the primary reason you don't see pits in modern car repair shops.

Even at domestic level, it would probably be cheaper and less hassle to buy and install a lift which only lifts by a metre or so than it would be to dig a pit.

Of course, you could do both and have a one metre lift and a one metre pit to give you standing room under the raised vehicle. ;-)

[That Bloke]

Strongman tools have a specific scissor lift with a 1m lift limit to be fitted over a an existing pit. It was modified from another lift designed to suit a particular client who had a shallow pit and limited headroom in his garage.

I'm affraid, I have >

[Matty F]

How about making a 1.1 metre high car-sized bump in the roof?

[David WE Roberts]

Just for clarification, why do you not want to do as the supplier advises? This would be a robust solution and give you the head room required. Given that you have solid foundations below, it should not be difficult to do.

As a win/win, why not install the car lift and then use that to raise the garage off the ground whilst you build the supporting wall? It would save messing around with Acro props etc.

Cheers

Dave R

[Andy Dingley]

Lifting (or dismantling & re-erecting) the timber structure and sitting it on blockwork sounds like the sensible option, but isn't this overall height going to have to go past the planners anyway?

[Tim Lamb]

I have done it! Mind you it was a farm building with a trussed/purlin roof. Block walls, concrete floor.

After freeing off the minimal anchor points and strapping the down slope side to the floor, I used 4 conventional Acro props plus one spare for when I ran out of thread, to raise one side:-)

Three courses of bricks were laid and the method repeated for the other side and ends.

regards

[That Bloke]

[That Bloke]

David

I thought jacking the roof and putting in the timber upper extensions could be completed and bolted within say 6 hours.

Jacking the full garage and building a block wall would have the jacked garage in the air for two days and if a high wind came up overnight it could be a bit iffy.

How long would you have to wait before the wall could take the garage weight and a drill to get the rawl plugs in.

On the other hand why not dismantle the garage first, the only extra cost is nails and roof felt plus some labour to get the nails and bolts out and in.

[That Bloke]

Thanks Tim,

Someone has done something similar.