Demolish and rebuild garage

tez_mike

Hi all
We were looking to do a single storey extension above the garage. Then came to the thought that the foundations for the garage are unlikely to be deep enough. A  couple of questions please.
Approx cost to dig a trial hole to check foundation?
Approx extra cost to demolish and rebuild brick single garage on top of the cost of the extension if required?
Thanks in advance

grumbler

The foundation is extremely unlikely to be sufficient. Old houses have very weak ones. Modern builders don't miss any opportunity to save money.

Digging 1m hole is a DIY job. You'll spend more time on finding someone willing to do such a small job.

DOH_a

It’s difficult, almost impossible to provide approx. build costs even with drawings as there are so many unknowns and variables.

Your best bet would be to dig a trial hole, have the foundations (if any) exposed and determined their suitability to receive additional loading. It’d be then be a decision based on costs as to whether you’d upgrade the garage structure for the new first floor extension or knock down and start again with two storeys. I’d always suggest and prefer the latter as it ends up coming with less complications even for the potential additional upfront costs. It also helps if in the future you decide on a garage conversion as you’d build the cavity walls from ground up.

FreeBear

A house nott far from me had a second storey extension done a couple or three years back. The original plan was to build off a block wall that formed part of a car port.... Until they found that the wall had zero foundations. Rather than knock the wall down and start from scratch, they had some piles installed and a steel framework to support a timber & rendered construction... Each to their own..

Slinky

Are there similar houses and garages in your street built by the same builder? Have any of them extended over the garage? If so, try asking them what they know.  We did what you are proposing to do but we knew we'd have to demolish and rebuild as lots of others had previously extended and it was a known fact the garage footings would not be deep enough. Regarding costing, ours was 10 years ago and part of a larger project so can't help on that one.