David W.E. Roberts wrote:


(1) How long is a piece of string :-)

Twice half its length...

(2) Looking at possibly buying a bungalow and converting the loft.

I assume from reading various threads over the years that the best way to go
would probably be to have steel beams inserted to provide the main load
bearing structure, and then joist and floor over the steel.

The "best" way, is to do whatever is necessary to get a supporting
structure for the floor that is "good enough". Depending on the spans
required, you may only need timber joists, if not then perhaps timber
joists with some flitch beams (a pair of joists with a steel plate
bolted between them).

I know neighbours who have been quoted abot ｣25k for a full loft conversion
of a similar area on a two storey house.

The real cost of said conversion is likely to be more - i.e. if builder
quotes 25K then you can expect the end cost (i.e. by the time you are
all finished and decorated) to be 30K or more. Builders obviously only
take the build as far as finishing the rooms - and tend not to include
the carpets and decorating etc. Also if there is a bath/shower room in
the conversion then they will tend to quote without the cost of the
fittings included since the cost of these will vary greatly depending on
what the buyer wants. Also remember to include the cost of preparatary
work - like in our case removing all the water tanks from the loft
before we started also required a change of boiler.

Does any one have a guide to how much the basic structural work (new load
bearing structure plus stairway) is likely to cost to give me an idea of how
much I can save by DIYing the rest?

Just played this game, so I have some numbers to hand. Not sure how
applicable they will be to your situation but they should give you a
ball park. In my case I am adding three new rooms to a three bed semi,
the new floor area is approx 35 sq m. The total cost of the floor
structure (i.e. joists, steel where needed, and fixings etc) was under
1500 for the materials. It took about six days to get it all installed
with two of us working. Contrary to popular belief, this bit is actually
not that difficult to do properly if you have a reasonable loft
structure in the first place. If you have a trussed roof however then it
is far more difficult!

Floor boarding adds say another 200 (for chipboard). Note you may also
need to install some extra sound and fire proofing under the new floor.
Chicken wire and rockwool will normally do it - but don't underestimate
the time it takes to install!

You will need to start with a properly engineered plan (with structural
calculations) to prove the floor design before you start. I got an
architect to draw a full set of plans (570 quid) - having seen them -
and worked out what software package he used for the structural
calculations - I would probably be inclined to do them myself next
time (if there is one!)

Stairs (in a typical loft conversion) would usually be one of the last
items to go in. That way you can isolate much of the work, mess and
noise from the rest of the house. I had various quotes for having a
staircase made up (with two quarter winders) that were in the 800 quid
range. That did not include fitting. In the end I decided to build my
own from scratch. Cost of materials works out about 200 ish - but that
does not include spindles, handrails, snazzy turned newel posts etc
which will cost extra depending on what you want. Took a couple of days
to make, and then another four to get completely installed. (if you can
get away without needing the complicated changes of direction a straight
flight would be much simpler and quicker).

Also don't forget to add the incidental costs like scaffolding (you are
not going to get a 4m long beam up through the loft hatch!). Cost of
full plans submission to the local council was about 264 IIRC yours may
be different (you are unlikely to actually need planning permission -
just building regs approval - but check with your district council or
architect).

Even with the lost space due to new floor and extra insulation I reckon I
should be able to fit in two bedrooms and a shower/toilet. This is withoput
a dormer of any kind.

The floor will add approx 5" - 6" inches from the top of the current
joists. The insulation (if we are talking on a sloping roof section)
will take away as little as 1.5" by the time the plasterboard is on when
you use things like celotex. Note however that you may need to make
changes such as adding soffit and ridge vents to compensate for the loss
of air flow to the roof timbers.

All very tentative at the moment - weighing up potential and future costs in
buying a detached 2 bedroom bungalow compared to buying a 3 bedroom semi.

Chances are you will add more value to the house than the cost of doing
it given current property prices - hence why so many people are taking
that route.

--
Cheers,

John.

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