DI- Why?
My job (as a professional builder) is to fix up DIY-gone-pear-shaped type jobs. Oh yeah, you know, the ones where the home improvement shows make it look incredibly simple to install your own skylight but tend to miss out the important roof engineering aspect of the job and rather just skip to footage of the magnificent finished product? As an example, I just finished repairing a skylight-gone-wrong where the homeowner decided to cut through a roof truss because it was "in the way". Total cost of just getting me (or similar) in to install the skylight: ~$500, total cost of getting me in to fix up the damage caused by a DIY attempt: $9,000-odd so far and I haven't even gotten all of the subcontractors invoices yet. (roof line drops, rain comes in through massive cracks in tiles that have crushed themselves due to massive power of roof line dropping, water pipes split due to roof joists pushed out of place from truss pressures, water running down wall cavities undermining foundations which then require underpinning etc etc... it adds up.)

I have some simple bits of advice for DIY house modification types:

1) Get a professional in
2) Get a professional in
3) If something looks like it's meant to be there, don't cut through it. If a professional put a structure in place while building the house, err on the side of caution and assume it does something useful.
4) Ask someone who knows what a load bearing wall looks like before getting your sledge hammer out.
5) Building regulations are in place for a very good reason, do not simply treat them as "advice"
6) Get a professional in.
7) Roof engineering is complex. You're dealing in tonnes when it comes to weight. You're dealing with weight that has to transfer to very specific places so it can be carried down to earth. Roof trusses and load bearing walls are not there just to look pretty (I think they look pretty), they actually do things!
8) If you remove some wall coverings and expose the house frame and you see a beam rebated into the studs on an angle, please don't cut it. That's called a wind brace. It stops your house listing in the wind. Please, don't cut it. Please. You need it. Simple rule of thumb: if a piece of timber in the frame looks like it might have taken a bit of work to install, you can assume it wasn't just put there for a laugh.
9) Yes, I know the storm water connection is close to the surface whereas you have to dig very deep to reach the sewer, but please don't be lazy and send your sewerage into the storm drain.
10) Putty and fillers are cosmetic, they're not structural.

Of course, I am being a bit harsh, another part of my job is fixing up so-called "professional" trades bodgy jobs.
(Brundy, Tue 8 Apr 2008, 13:37, 1 reply)

Too right.
May I add to Brundy's 1, 2, 5 and 6, if a jobber tells you he'll take the last thousand after the job has passed inspection, shoot him. He's planning on doing a crap job and then fucking off, leaving you holding the bag and lamely explaining to the building inspector how "he said it was up to code".

Get a professional in.

signed,
A. Victim
(TDub Nunc id vides, nunc ne vides on, Tue 8 Apr 2008, 17:39, closed)