Advise on milling fir for building materials

[marlon]

Hi, we are firewood merchants so access to lots of good timber - now I'm just about to start building a very large "workshop" in my garden ( some might call it a granny flat!) I'm going to be building the main frame out of 4 x2 and 6 x 2 for the roof. I have a friend who has a mobile sawmill so is it feasible that I could rip down my softwood cord into the said sizes? Would I need to leave for a while once milled or could I use it straight away? Same question with the cladding I'm going to mill some oak I have into the feather edged boards. Thanks in advance

[pgkevet]

It's a good question and one I;d like to hear the answers to from folk who've actually done it.

 

There's vids of folk who have built whole houses like that but it strike sme that the problem with pine is going to be preserving softwood thats used green compared to buying pressurise tanalised stuff.. and potentials for waring under load.. and difficulties in it drying if you build with vapour barriers and insulation..let alone the issue of woodworm in the fresh timber if it hasnlt been heated/seasoned first..and on two's that'd be at least a year unless you build a seasoning chamber.

 

The cladding would be less of an issue

[tommer9]

No you can use it green, thats fine. Larch, Douglas fir are the most comonly asked for construction softwoods IME, and both will work fine with green oak. Beware that you will be paying more than normal to you sawyer to use cordwood rather than sawlogs as there is more work involved with smaller diameter timber.

[Justme]

Beware that you will be paying more than normal to you sawyer to use cordwood rather than sawlogs as there is more work involved with smaller diameter timber.

 

Plus your recovery rate will be lower & the "wastage" higher.

[Timmy C]

Hi, I built a workshop for myself earlier this year from trees I milled with an Alaskan mill and a large bandsaw. Constructed of 4x4 and 6x4 timbers, I used some traditional joints along with other modern fixings to make life easier. The timber I used was part seasoned and well treated with various anti woodworm and fungus paint. Still standing strong and has survived high winds a few times now with no issues.

 

Good luck building yours!

[aswales]

For cladding it will be fine in the green state, however for structural frame members be more of a problem, you will have to factor in shrinkage into design and whilst green the timber will be less strong. As timber seasons it dries out and loses water from it cells and shrinks, during this process the structural strength, stiffness and hardness of the timber increses which is at its best when it has become dry and stable.

 

The shrinkage you need to be concerned about is the across the width of the timbers, where that dimension is important to your design sizes.

Watch out for timber containing tensions from reaction wood, this is generally obvious because it will bow and twist as soon as its been cut from the sawlog as the tensions in the timber are released.

 

If you do build a green frame with green cladding give it chance to dry once the frame is up and externally cladded, wait before you fit door and window openings to allow for shrinkage of top and bottom wall plates.

Don't fill in anywhere with insulation between the members, there 's nowhere for the water to go that is released during the seasoning drying process, it would just get trapped and the timber will rot and grow mould....

 

If I was you, would at least dry your framework timber and just use green on the external cladding.

[marlon]

Dare I ask if leylandii would be any good??!! Just happens I have a job tomorrow in which I'll be felling lots of straight lengths approximately 18 inch stems which I could keep for free otherwise it'll be burnt. Thanks for most interesting comments, i take on board comments about the disadvantages of using green softwood - I presume the same would apply for oak? I have around 40 tons of oak which could be used for the framework it just seems a shame to use it for the frame which will be covered over with plaster board - on the otherhand it'll only go for firewood so it's not as bad as it sounds! The oak was standing deadwood so the moisture content will be lower than normal.

[agg221]

It will work. However, in addition to the very valid comments above, a couple of other points:

 

You're almost certainly not subject to building regs, but in the unlikely event that it's big enough that you are, be aware that construction softwood should be graded, yours won't be, and probably wouldn't pass if you tried.

 

Different softwoods have different properties, both strength and durability. Strength is unlikely to be relevant here, but durability will be highly relevant. You can't pressure treat and are unlikely to be able to buy anything that works in the long term. Don't assume that non-durable species automatically rot - think of the inner layer of straw on thatched houses, which is often original and centuries old. But, if they get damp, either through poor design or temporary exposure, they will respond differently. Larch is reasonably durable, Douglas fir heartwood is good (but you won't get much out of cord and it's a pain to separate), other species are less durable. Larch is long grain, so tends to warp more, but is strong.

 

What sort of sawmill does your friend have, and have you specifically considered how you'll make the feather edge cladding? Traditionally, this is made by milling square edge boards, planing the outer faces (if painting) and then ripping down near the diagonal, leaving 1/4in one side, 3/4in the other, so you usually need a planed thickness of 1in plus kerf. If not planing, this is slightly easier as you can cut the boards feather edged directly. But, even if you can adjust the height of the mill head over the log independently on each side, you still need to cut your cant square edged before you start cutting, and be very careful about how much you move the head down on each alternating cut - it won't be the same amount unless your log is centred on the bed.

 

Speaking from the experience of having milled enough 8in wide oak feather edge this year to cover my two storey extension, it is tedious.

 

The fixing technique for feather edge of this type is a single fixing through each board, just above the overlap with the board below. The bottom edge is therefore fixed down, but the top edge is free to float slightly (although trapped by the board above so it can't warp). This stops it cracking as it expands and contracts depending on the weather.

 

Alec

[agg221]

Dare I ask if leylandii would be any good??!! Just happens I have a job tomorrow in which I'll be felling lots of straight lengths approximately 18 inch stems which I could keep for free otherwise it'll be burnt. Thanks for most interesting comments, i take on board comments about the disadvantages of using green softwood - I presume the same would apply for oak? I have around 40 tons of oak which could be used for the framework it just seems a shame to use it for the frame which will be covered over with plaster board - on the otherhand it'll only go for firewood so it's not as bad as it sounds! The oak was standing deadwood so the moisture content will be lower than normal.

 

Leylandii, like any species, will work. It will probably be very knotty though which will make fixing a total pain.

 

The oak would definitely be strong and durable, and a nice timber to work with. Could you make the frames a bit deeper (say 5x3 rather than 4x2) and cut the plasterboard to fit between them (ledged on small battens, milled at the same time)? If so, you could create an exposed internal frame, which would be very traditional and quite attractive (our house was built this way - obviously wattle and daub rather than plasterboard) in about 1500.

 

Alec

[aswales]

Have a look at a text on green oak building, theres plenty of material on this around and the basic rules apply to most timber framed buildings including softwood.

Leylandii could be used, lot of small knots, no reason why not, not grown as a commercial timber species for timber production that I'm aware of but some members of the same family are used in certain parts of the world.

If your oak is from standing deadwood, a lot of the timber can be sound, moisture content may be reasonable. Would be a good use, certainly better than firewood...Have you a moisture meter ?