making use of Garage loft space.....

[Stephen]

Hello all,

I have a "semi-detached" garage that is attached to the residence if that makes sense.

Its of typical 2.5m by 5.0m long dimensions.

It has 5 Fink trusses on it with a stonewold tiled roof.

I have been given a load of flooring joists that are 3m long and would like to turn the garage loft into a usable storage space to be accessible by a loft ladder.

Now, As you open the up and over garage door, to your right there is a double skin wall between the garage and the main house which is of clinker block construction (both skins)

On the left hand side there is a single skin brick wall that has two brick pillars about 2m in and 3m in. There used to be a window between these two brick pillars. This window has beeen removed and bricked up. The original steel lintel has been left in place and is supported by the two brick pillars.

My proposed plan is to cut a rectangular hole 2.5m of the way into one of the skins of the double skin wall.

I would then put a pair of sistered flooring joists into this hole and the other end to sit on top of the original window steel lintel. (this lintel looks like it was originally meant for a double skin wall so it has a ledge on the inside between the two brick pillars. The top edges of this sistered joist would come up to the bottom edges of the fink trusses.

I then plan to fit two sets of flooring joists, one set from the steel lintel that is above the garage door to the sistered joist pair. The 2nd set would run from the back wall which is a double skin wall to the sistered joist pair. The span from the middle to either front or bac of garage will be less than 3m.

Now does this sound structurally sound so far? The query I hhave is that the sistered joist will effectively sit on 4 inches of support as opposed to the recommended 6 inches, which is why i think sistering the joist could be helpful as that doubles the support contact area.

Now I was wondering what to do about the Fink trusses? There are 5 of these.

Access to these trusses is easy from the inside as there is no ceiling in the garage.

The outer two fink trusses I am not bothered about as they are up against the gable walls at both ends. So that leaves 3 trusses. Can I convert these into Attic trusses with some suitable carpentry to make better use of the space?

I then plan to put a chipboard caber floor in this loft space and fit some lighting.

Any comments?

S.

[stephenten]

I know that if it was a full on loft conversion then structural calculations are needed and there are firms such as telebeam or trussloft that specialise in such conversions.

Now for a simple fink truss loft over a garage, going to all this work will mean that it's not cost effective for a simple storage space.

The new joists and floor would be independent of the trusses and sit alongside the trusses so no extra load is imparted to the trusses themselves.

I was hoping someone on this Ng might have done something similar?

[Andrew]

Looks like overkill to me. What depth will the sistered joists be ?. How much headroom will you lose doing it this way ?. After you have bashed your bonce a few times you might wish you hadn't.

Unless you are going to go the whole way and replace the trusses with purlins and stronger rafters, you still won't have much easy working space up there.

[newshound]

What you propose doesn't seem unreasonable, and you seem to have a pretty good idea of what you are doing. As the other poster said your existing trusses are not likely to have much margin, but can you find an "attic truss" design on-line to give you an idea for detailed design?

[tabbypurr]

If you want to make good use of the space, getting rid of the forest of matchsticks is necessary as well as adding load bearing capacity. Can you fit new trusses before deforesting the finks?

NT

[stephenten]

I have had a thought.

I had a look at how trussloft do their conversions (take a look on YouTube)

I could use some angle iron on both sides of the trusses at the top horizontally to form a closed triangle and bolt through

I could then get some angle iron welded up into a 2 shape where the straight but would be on the new floor joists and then the vertical bit would go up vertically upwards and then carry on up until it met the horizontal angle iron mentioned earlier.... Think of it as an angle iron version of an attic truss that could be bolted and screwed to existing trusses. The w bit of the fink trusses could then be cut out.

What do you think?

[tabbypurr]

Why do you want attic trusses rather than simple triangles?

NT

[stephenten]

I can live without a bit of space at the eaves and at the apex from the formation of the new structural triangles as then bi can cut out the w parts of the fink trusses. This would give me a usuable attic loft space....

[tabbypurr]

If you form triangles from sufficient new timber/steel you won't need to lose those bits of space.

NT

[Jim K..]

Roof trusses are invariably designed & built as cheaply as possible, so any such modifications need full consideration by someone who knows what they're doing....

[Jim K..]

It's not extra load that's the problem, it's making fundamental changes to minimally speced cheapest possible roof trusses where your biggest gamble lies

and then hope they knew what they were doing!?