post and beam timber frame

[Stereo]

Wow, that's stunning! What species are you using in the build? Is it mixed. Is that oak for the main timbers?

 

I'm thinking of something similar and the main woods we have around here are sycamore and hazel. Not sure if they would be up to the job. I guess sycamore would take good load but not sure how durable it is.

[agg221]

Wow, that's stunning! What species are you using in the build? Is it mixed. Is that oak for the main timbers?

 

I'm thinking of something similar and the main woods we have around here are sycamore and hazel. Not sure if they would be up to the job. I guess sycamore would take good load but not sure how durable it is.

 

Sycamore is very non-durable, but that can be coped with. Oak is usually preferred because of its high strength so designs can use thinner sections. It's pretty durable, but consider that an oak fencepost will rot through in no more than about 50yrs, while timber framed houses will last for centuries.

 

It's all about design. The structural timbers have to be laid out in such a way that they're not exposed to damp. That's about detailing and barriers where necessary - there are some really good publications from TRADA that relate to this.

 

For context, a few of the surviving early medieval cruck frame blades are poplar, and the innermost layer of thatch on many medieval houses is still original - 500yr old grass!

 

Alec

[Stereo]

Have lots of alder but hadn't considered it.

[canoehead]

the frame is a mixture of different woods. mainly maritime pine, because that's what i have largely (half the posts, all the sill plates, floor joists, girding beams, tie beams, the roof plates, rafters and purlins) a fair bit of walnut (most of the rest of the posts, most of the braces, all the collar ties, most of the queen posts, most of the girts, and some of the windbraces) some chestnut (braces, windbraces, couple of queen posts, and some of the girts) and oak (windbraces, and all of the pegs). alder and willow braces going in the proposed bathroom extension.

 

i had done a fair bit of restoration work on timber frames when i lived in england and although when you think of timber frames you tend to think of them as oak, often that isn't entirely the case, many species were used, often in conjunction, mainly because they used what was available and appropriate. its about thinking what are the inherent strengths of each species and how can you best utilise them, each situation can require something slightly different, but essentially in framing its either acting in tension or compression, and sometimes both.

 

you could use alder anywhere you would use oak, awesomely strong, stunning coloring.

 

i would have loved to have used oak, (next time if there is one) but don't have much, and i saved the chestnut i had for shingles. it was all about trying to use what resources i had in what i thought was the most useful way. my whole approach harks back hundreds of years to the old ways of doing things, how would we have done this before, when you couldn't just go to the store and buy it? partly because that is my situation, stores don't exist here the same way as back in the first world, and i don't have any money.

 

(alec, do you have any pictures of popple crucks? and are they hewn? i would love to do a cruck frame. have improved my hewing by changing my finishing stroke to one like skinning even worked on very dry walnut hearth lintels)

 

regards rick

[agg221]

Hi Rick, I haven't got an photos myself but there are quite a few if you google it of the barn at Avoncroft. This one is quite good:

 

Inside the cruck-frame barn | Flickr - Photo Sharing!

 

There's also some discussion in the very useful "Regional variation in timber-framed building in England and Wales down to 1550; the proceedings of the 1994 Cressing Conference".

 

I believe the earliest cruck blades were hewn, but that meant finding two trees with similar curves. Later ones were therefore ripped centrally down the two lengths and the halves used as a matched pair of blades.

 

Alec

[canoehead]

great barn alec. nice pic. i was thinking riven and hewn. anyone got any examples?

[teepeeat]

Rick, did you ever consider building using timber in the round - ala Ben off grand designs?

[canoehead]

i loved that episode of grand designs, and i think what ben law did was really inspirational, but to be honest, for me, it was never a consideration; (at the risk of being shouted at) i feel round-wood construction presents too many problems and not enough solutions.

 

what i thought was inspirational was buying a woodland, using it to build from and to help enable a degree of self-sufficiency, which is something i took to heart.

 

i know you only asked a question, but the answer is complicated (for me).

 

my issues with round-wood construction from a structural pov, are that there are no span tables that indicate what size timber you need in what situation. with sawn timber it possible to determine fairly accurately what dimensions you need for posts and beams (there are calc.s all over the place which prove it).

 

in both scribe and square rule framing you can allow between 15-20% wane on any timber, within any size classification, suggesting to me that round-wood is no more than 15-20% stronger; which leads to what i think is the biggest issue in round-wood construction; the assumption that timber being stronger in the round will therefore allow you to downsize the timbers you need, subsequently under allowing for deflection. timbers in a frame have to be stiff as well as strong. timber frame timbers aren't just big because of the clear spans, they also have to absorb beam deflection in live and dead loads. posts and beams need stiffness. the more you remove to house joints the less stiff your beam becomes.

 

what i like about sawn and hewn timber is the (relative) evenness of sizing and meeting places of edges, which eases the integration of other surfaces. where as, working in the round means constant scribing, or for instance, flooring, means cutting the top surface and or a lot of shimming.

 

additionally, its not easy to mate two round surfaces, which limits the type and variety of possible joints you can use, and there-fore the situations in which you can use round-wood. i wouldn't want to set-out and cut an english tying joint at plate level in the round. its complicated enough square. for me, that's what it boils down to, over complicating something that's supposed to be relatively simple and beautiful as a result of its simplicity, for me it would undermine or take that away.

 

if you can solve the structural issues, i guess its a whatever you prefer thing. my background is in traditional carpentry, so i don't really care for working in the round, in terms of general house construction, its too time consuming for me, and doesn't provide the kind of evenness of finish i'm looking for. and if i had built in the round my wife would've left me.

 

what i would like to do (given the opportunity) is build a completely hewn cruck and arch braced truss frame house. anyone?

[teepeeat]

Hi Rick

Apologies for the very short, simple question - posted in a bit of a rush with my mind on other things.

Luckily, you seem to have picked up on what I was after and made some very interesting points.

Like many, also found the program very inspirational on many levels.

I dont have your technical knowledge or experience of these things, but am looking to build something in the future and am therefore asking a lot of silly questions.

As I said, a number of interesting points, but just wondering if the time taken to scribe joints and pack floors etc can be offset against the time you have spent hewing and squaring timber?

 

Have you seen the detail of Ben Laws joints - one was called the 'butter pat' joint. Blimey - just realised how well named that was as it just popped from some dark recess of the head from a few years back looks exactly like a pair of butter pats

Anyway, it seems to be a good solid joint requiring minimal removal of wood, presumably to limit weakening the timbers too much? Will look it up and post something if you havnt seen it.

 

As you say, round vs square timber will depend on personal preference, but would have thought only to a certain degree as it may also be dictated by what timber is available.

In Ben Law's case it is predominantly coppiced sweet chestnut, but I guess he is also looking at expanding the market for coppice products which does cloud the arguement slightly.

 

I have to admit I do like the aesthetics of the round wood and was under the impression that it would reduce the overall labour required in a low tech build??

 

Regards

Terry

 

PS, your build is doing a fair bit on the inspiration front as well - for quite a few on here besides me.

Edited July 2, 2012 by teepeeat

[canoehead]

here's the frame pretty much complete, just the bathroom extension to finish, the roof of which segues into the main roof (will post when done).

the chimney took me 2 1/2 months in 40 degree heat, its 1m deep x 2.2m wide and 10.5m tall, 3 flues, hewn walnut lintels, a 250mm stone face over a 200mm blockwork skin, clay flue liners and vermiculite type insulation. (i'm not a brickie, i didn't even used to lay much block work in the uk, let alone do stone work, that's why it took so long)

had to buy in some (12) of the rafters as i ran out of material (sorry to the purists) and had to have a hand lofting those 12 (4x7's x 5m) as they were very green and weighed 300-400 lbs a piece (hard enough to lift on my own, almost impossible to loft) and i didn't want to risk mashing the purlins (more specifically the joints on the purlins) trying to get the rafters in (again sorry for my lack of effort)