Future proofing garage base

[arseneknows]

Hi

Last year a tree fell down in my garden which completely destroyed my prefab double garage at the end of our garden.

We had plans drawn up initially for a detached outbuilding, planning was granted. However we cannot afford right now to do the full build (other half wanted instead to add single storey extension to the house . Therefore I will probably pay for a new prefab garage to go back up as we need the garage back. It will be slightly longer than before due to the extra space afforded by the removed tree. 21'3 by 18'3 instead of 16 x 18'3

Looking for some advice, I do at some point want the option of removing the garage and do the proper build.

Is it possible and worthwhile doing the proper footings now? Even for a prefab garage? How would this work or what would it look like? Thanks.

 

[oldbutnotdead]

Not just possible but a very good idea- if you don't start the build then your planning permission will expire. Foundations count as a start.

You'll need to put a building notice in as well (for your full outbuilding), dig the foundations as per plans/BCO local advice (prob 200mm strip at 700mm below ground) and get the BCO to approve the trench,then lay foundation blocks up to DPC (BCO check), do your slab properly (hardcore/sand/DPM/concrete, don't forget ducting for services in the future) and then stick your prefab on top.

Any time in the next millenium you can then junk your prefab and build your proper building - Building Control will probably want another fee but that'll be it

 

[arseneknows]

Thanks OBND.

I'm not a builder so its worth knowing from someone in the know!

Before I thought of doing pre-fab I asked a builder to quote for getting the outbuilding out of the ground, up to DPC (but this was with the intention of just leaving it at that until I could pay for someone to complete the build).

He quoted £8K

The prefab garage delivered and installed is £8.5K. so £16.5k for the prefab option.

I did float the idea with the builder to do a single skin brick wall garage with proper building regs footings, DPC, insulated floor, roof, roof lights, garage door instead of bifold doors. etc. But that option was £25K The option then to complete later with timber internal walls, insulation, etc.

The proper completed build quote (original spec) was almost £50K, ie outer brick walls, inner block, more rooflights, bifold doors, WC, etc. Like a habitable bungalow so a lot more work I guess. Way too expensive on top of my single storey extension. Cant do both.

Decisions Decisions!

 

[oldbutnotdead]

Think I'll move to Berkshire and start building garages! That price out of the ground sounds high even for an insulated base and double skin wall- unless you're on bad ground and need stupidly deep foundations or access is tricky or there are big trees nearby. You might want to have a shop around.......
And that prefab had better include erection for that sort of money- oh but it does, just reread original post. Doh!
By the way, if you go for the bigger prefab option (the 21'3 x 18'3) you'll need building regs on it (greater than 30 sq m). Won't be onerous but worth remembering- the supplier may or may not prompt you on it.

 

[arseneknows]

Thanks again.

Yes you should move down to do my garage , sounds like it would be a lot cheaper. Even if I put you up for a week lol.

What would be a more reasonable price bearing in mind everything is inflated around here!

The ground is good, and access is excellent. 18 ton lorry can drive right up to the site no problem. In fact they pumped concrete in for the house extension foundation and that's further away from where the garage is.

Yes prefab garage is all inclusive of delivery and installation. But extra 3k for a new slab base because they say you can't just extend the old base by 5ft, you have to re do it all.

I paid for pp and building controls on new garage building. I assume BC will be involved only up to DPC level if I then decide to put prefab up for now?

 

[tony1851]

I paid for pp

Did you actually need planning permission?

 

[arseneknows]

Yes, the plans are for a building 8m x 5.4 m, over 2.5m tall right up to a boundary on 3 sides.

Actually I might have to rethink the size of the prefab garage as the original planned building is larger than the prefab. The prefab company said that the concrete slab shouldnt be more than 50cm than the actual garage dimensions.

 

[oldbutnotdead]

Materials and wages for your foundations and slab comes to about £5000 (from my fag packet sums and adding 30% for Southern wages) so there's a fair chunk of overhead in those prices- not as much as at first glance but 60% is a bit fruity. Skips are a big variable- I've heard tales of £200 for 8 cube in the South, if that's the case then that's £800 less profit on the job and down to about 38% profit which is a bit more reasonable.

And don't get too worked up about the excess margin on the slab- the prefab suppliers will be concerned about rainfall on the concrete getting under their structure and (if it is timber) rotting it, if it is concrete/steel rusting it or going underneath and wetting the internals. Some big planters or some DPM and a rockery will solve that one

 

[arseneknows]

Thanks again.

I will budget for around 5K for the footings and see if anyone is prepared to do it for that.

I checked with the prefab garage people, they said their structure is 4 in thick and can be placed onto a single skin wall so perhaps I don't need to worry about putting it on the slab but instead the wall itself. Although this will be at ground level I would hope else the garage door will need to be taller than 6ft 6.