Extension over the garage cost

imalwayshappy

Registered User
Messages
137
Hi,

I am considering building an extension over the garage in my home. Its a standard 3 bed semi. I am told (without foundation by someone) that building an extension over the garage is very expensive (I don't know why) far more than a similar sized extension that would be build on the back of the house for example. Has anyone had any experience with this? Is this actually the case?

Thanks
 

Leo

Moderator
Messages
13,187
What's there will need to be surveyed to assess what the options are. It may be cheaper knock the garage and build a new two story extension. That would bring the benefit of better insulation below the ground floor.

Even if there is a foundation under the garage, it may not be sufficient to support a two story extension, so expensive underpinning would be required.
 

RedOnion

Frequent Poster
Messages
6,208
It can be expensive.
Firstly, you're making an assumption that the foundations & walls of garage can support the structure. That might not be the case.

You'll be taking off the existing roof of garage before you start. Leads to internal replatering, etc.

The other part is it depends on the existing roof structure of the house. Say for example you've a hipped roof, you're going to be rebuilding quiet a bit of the existing roof structure to bring it out over the extension. To get roof to 'blend', it's also common to strip the tiles from back of house to put on front, and recover the back completely.
 

Dublinbay12

Registered User
Messages
657
@imalwayshappy did you progress this any further?

I am starting to look into rough costs of extending over the garage and attic. With all the commentary on rising construction and material costs over the last 12 months I need to figure out if it is a non starter. Standard Semi-D 1960s build with a hipped roof.

I know this question is equivalent to 'how long is a piece of string'. I have seen estimators at 2-3k per sqm, therefore a 30sqm extension at 3k would come in at 60-90k, is that a reasonable estimation?

I am really trying to figure out is this going to be a 100k job, 150k job or a 200k job for the basics before factoring in finishes and ensuites etc.
 

cremeegg

Registered User
Messages
3,676
@imalwayshappy did you progress this any further?

I am starting to look into rough costs of extending over the garage and attic. With all the commentary on rising construction and material costs over the last 12 months I need to figure out if it is a non starter. Standard Semi-D 1960s build with a hipped roof.

I know this question is equivalent to 'how long is a piece of string'. I have seen estimators at 2-3k per sqm, therefore a 30sqm extension at 3k would come in at 60-90k, is that a reasonable estimation?

I am really trying to figure out is this going to be a 100k job, 150k job or a 200k job for the basics before factoring in finishes and ensuites etc.
Knocking and building from scratch should cost under €2k per sq m. That does depend on location and site access of course.
 

lucky1!!

New Member
Messages
2
hello, we are also extending above our garage. A builder dug a hole and engineer has certified that foundations will support a second story. You coould do this, it wasn't that expensive.
 

DeeKie

Registered User
Messages
761
hello, we are also extending above our garage. A builder dug a hole and engineer has certified that foundations will support a second story. You coould do this, it wasn't that expensive.
Interested to know the rough cost of the engineer test please?
 
Top