Log Cabin Installation Guide
Log cabins are made of a natural material and it is impossible to guarantee an absolutely perfect finish to every part because of the natural movement of timber. You must therefore expect to be prepared to carry out some finishing/alterations yourself. By definition you must be a competent woodworker and have the appropriate tools (saw, hammer, chisel, drill, etc.). If you feel that you might not be capable of carrying out this type of work then you should look to employ a suitable contractor who is able to do this for you.
Your cabin will be delivered in one large pack. The first part of the installation process is to unpack the individual items within the main pack and stack them near to the proposed site for the building, at the same time counting the parts and checking them off against the parts list which is supplied with the building. This stage is very important and you should not start to construct the cabin if there are any missing or damaged pieces. If the kit is incomplete you should report this immediately.
The diagram below shows a typical excerpt from a base plan supplied with one of our cabins:
This plan shows a typical floor bearer layout for a cabin with an overall dimension of 3.0m. The interlocking notch is typically set in by 0.1m from each log end, hence the base measuring 2.8m. Please note that the plan shows the spacing between each of the bearers as well as the width of the bearer on plan view. Floor beaerers are always laid flatways in order to allow for the floorboards to be fitted at the end of the job as described later on. Please note that they are called floor bearers and not floor joists, this is because they are designed to be supported by a sub-base. They are not designed to take the full load and span from one side of the building to the other.
It is good practise to lay a damp proof membrane (DPM) on top of your base before starting to install the building. If the base is over-sized, the DPM should be cut about 200mm larger than the base size required for the cabin, it can then be folded over on top of the floor bearers and trapped by the first course of logs to make it stay in position. This means that should water get on top of your base and under the building, the water will stay under the DPM rather than get on top of it, keeping all of the timber dry. Ventilation holes can then be cut sufficiently above the base level, if required, to keep the standing water at bay.
Once the floor bearers are positioned (please refer to note 9b), the first course of logs can be fitted. Log cabins use interlocking joints which rely on a staggered log height, consequently the first course of logs consists of alternating full height logs and half height logs as shown below:
Build the walls as shown on the plans provided, sliding the windows and doors into position when there are around 5 courses of logs built up either side of the window/door which help to hold them in place whilst you carry on building (please refer to the extra instructions supplied if you have upgraded ISO windows/doors). You can screw the frames through the bottom piece of outer frame into the log directly below but it is important that you do not fix any window or door frame directly to the logs higher than this. You can use packers to stop any unwanted sideways movement at the top of each of the frames (only use packers on the sides of the frames - they can be screwed or tacked onto the frame to hold everything in place- do not put packers on top of the frames as this will not allow the logs to settled down after the build is complete or during the change of seasons) - there is a deliberate gap either side to allow for final positioning of the frame. If you find that the door lock has the latch pointing in the wrong direction, you do not have to take the mechanism apart to change it but merely either pull the latch out, twist it round and click it back into place or push it in by releasing the gravity toggle, spin the latch around and click it back into place.
If the cabin has over-sized or heavy doors (ie garage doors), then they should be fitted as follows-
The coach screws should not be fitted until you have finished building the cabin and you are sure that both the logs and the doors/door frame are true and straight. It can depend on the time of year as to where exactly you fix through the slots – the cabin will always settle down after you have built it but it will then also either contract further if you are building in the winter (the building is always slightly taller in the winter as opposed to summer when the logs will dry and shrink), or expand if you are building in the summer. This can always be altered at a later date if the screws get too close or touch the ends of the slots – the higher up the building, the more accummulative movement there is). This fixing method will stop any sideways movement of both the logs or the door frame.
If the cabin has a wall longer than 6m, then it should be built as follows:
The logs are joined in the middle of a partition wall or portal archway. The metal plate is supplied in long lengths which can be cut to length on site with snips or hacksaw. The joining logs should be tightly clamped and then fixed using a screw through the metal plate either side of the joint which will stop the logs spreading in the future (these screws should be angled away from each other slightly as this will pull the joint together and also increases the pulling strength of the screws). Every course of logs should be joined in this way.
NB- this method is not possible with 28mm logs as the banding is too wide to fit, therefore the 2 joining logs are each pilot holed and screwed into the common partition/archway log with appropriate fixings.
Fit the gable trusses into position and secure by sliding the main roof purlin supports into the appropriate pre-cut notches in the gable triangles. If the gable triangles are supplied in more than 1 piece (sometimes they are too large to be supplied in one large triangle), then each additional piece (whether individual logs or number of logs already fixed together to form the top of the gable triangle) should be glued and screwed to the previously fitted part of the gable triangle (whether they be at either end of the building or an internal archway/partition) using long heavy gauge screws.
If you are building a twinskin cabin-
a) It is important not to fill the cavity up to the top of the walls because the walls will settle down and therefore the insulation would be exposed and could force the roof up. We suggest leaving a minimum of 60-70mm gap all around the top. The same rule applies below any windows where the logs could also settle down - leave a pro rata gap depending on how many logs are below the window.
b) Make sure you insert the threaded rods into the corners of the cabin, making sure that there is enough room underneath to periodically tighten the nut until it tightens no further (usually in the first summer after the installation when the timber is at it's driest)
(a) If you have an insulated roof/floor, the construction is as follows:
Screw the timber flanges to the underside of the purlins and screw the coving support to the side walls. We provide lengths of T&G boarding that will require cutting down to suit the gaps between the purlins (these should be cut around 10mm shorter to allow for movement and irregularities between the purlins). Lay the short lengths of T&G boarding between the purlins, resting on the flanges. Making sure that there are 10mm spaces at the start and finish of each bay in case the boarding swells.
When each bay is complete, lay the polythene vapour barrier directly on top of the T&G boards, lapping it up all sides, then fix the holding batten into the purlin on top of the T&G and vapour barrier. This allows for movement in the T&G whilst holding it all in place as well as sealing the vapour barrier all around as well.
Fit the insulation between the purlins. (If you have the solid foam insulation kit, this will comprise of 1 layer of solid foam insulation placed directly onto the short lengths of T&G and then 1 layer of 100mm fibreglass insulation over the top which will fill the whole of the cavity making a "warm deck" roof). Make sure that it is a tight fit all round.
Once this step has been completed proceed to the next step. It is possible to complete this step after the main roof has been fitted but it is much easier to work from bottom to top with a 2 layer roof.
(b) The photo below shows how to close off the under floor insulation from being exposed to the elements.
The timber fillet can be simply fixed to the ends of the bearers, or if you wish, the bearers can be trimmed a little to allow for the thickness of the fillet (each fillet being 8mm thick) and therefore giving a flush finish.
Nail the tongue and groove roof boards in place by starting at one end and working along (2 nails in each board at each junction with the purlins), checking the distance covered at the top and bottom of the boards to ensure they are running parallel to the walls (this will avoid cutting a wedge-shaped final board).
NB Do not fix the roof boards tightly together as they may swell and cause damage to your roof structure and felt.
Fix the side baulk / drip batten to the underside of the protruding Tongue and grooved roof boards along the eaves, this will then form a drip for your felt to dress over (can be used in a number of different orientations as shown on the diagram):
Once the felt has been fitted, the barge boards and fascias can be fitted which helps to hold the felt down.
Now the building has been weathered in, it is safe to lay the floor without danger of it being exposed to the elements. Use the same principle as used with the roof, ie. start at one end and work towards the opposite wall, always checking that the remaining gap is equal at either end of the boards to avoid having to cut a wedge shaped final board to finish.
NB Always allow at least an 8mm gap between any wall and the floor boards to allow for expansion.
Fit skirting boards and any finishing trims that are provided.
Finally fix the clamp baulk as shown below:
Once the cabin has been installed it is very important that it is painted with a high quality preservative/stain immediately (all of the exterior as well as the interior including the ceiling), the exterior coating must also be water repellent.
It is very important that anything fixed in the vertical direction is done so using flexible joints (ie slots) to allow for future log movement (ie- shelving, electrical conduit, cabinets, etc.), and allowing at least 50mm of expansion or contraction gap.
Adjustments: Once built, log cabins will take approximately 2/3 weeks to "settle down", where the height of the building will reduce by at least 25mm. Inevitably this could cause some of the doors/windows to bind slightly, this is easily rectified by using the adjustable hinges to re-align the door/casement. We are not responsible for these adjustments.
Sometimes the frames may need re-squaring as well, again this is easily done by unscrewing the 2 internal side architraves, re-squaring the frame (equalling out all of the clearance gaps around the casement/door), temporarily wedge in place, then measure the gaps between the frame and the logs at either side of the frame, cut some packers just slightly less than the gaps (you do not want to wedge it so tightly that the logs are unable to move up and down) and screw or tack the packers into place. Finally remove the temporary wedges and replace the side architraves.
Further helpful hints and advice can be found at http://www.hortonsgroup.com/faqs