Log Cabin Foundation Beams

Log Cabin Foundation Beams

We offer a five options for your log cabin. These beams are designed to sit between the first log and the base of your log cabin and act as sacrificial timber to prevent the first log ever sitting in water. Further details on bases can be found here: Log Cabin Base Advise

These are optional and do not have to be used within the build.

Please note that any height dimensions given for the log cabins cabins EXCLUDE the additional height created by a foundation beam.

If you were in any other part of Europe buying a log cabin nothing would be supplied but we prefer to supply at the very least a standard foundation beam and these will be sent with every building.

It is often the case that other UK suppliers of log cabins also do not supply foundation beams. Many customers will buy ours even when they have sourced a log cabin from elsewhere.

In addition we also offer different profiled foundation beams. These will not provide any extra longevity and is a choice of Aesthetics. They do ‘present’ the cabin slightly better and the slope allows water to wick away from the bottom of the log.

Profiled beams are available in the following:


This is tanalised / Pressure treated timber with the dimensions of 44mm x 70mm and 2.40m in length. Longer timber can also be supplied if required and this is very useful for use as floor joists as well if you are using a pier type base: Foundation Timber

The video below shows how we fit the standard foundation beams. It’s a good idea to set them in 1- 2mm this then provides a natural drip stopping water from running under the log.

A corner cabin will have a cut angle of 22.5 degrees and two of these will form the 45 degree angle required at the door.

When using standard foundation beams the base is made to the minimum footprint dimensions shown on the product page of your log cabin.


The video below shows how we install the profiled foundation beam. This is applicable to all of them. Please note it is necessary to adjust the upstand when the corner interlock. This may also need to be removed when placing the doors.

For profiled foundations base dimensions are often increased to account for the slightly wider footprint. Please see the following diagrams for guidance:

28mm profiled foundation beams

Profiled-foundation-base-advice 34mm

Profiled-foundation-base-advice 45mm

Profiled-foundation-base-advice 58mm


Standard foundation beam being used in a build

Standard foundation beam being used in a build

Hardwood foundation beams in use

Hardwood foundation beams in use

Composite foundation beams in a log cabin build

Composite foundation beams in a log cabin build



54 thoughts on “Log Cabin Foundation Beams

  1. About to construct a Thurin with composite foundation beams. As this is an open-front d structure, rain will likely get inside. What do you recommend under the beams; DPM, silicone bead or nothing? I intend to fix the beams to the concrete base, as fear wind getting in and lifting ,,. Good idea?

    • If it is the composite ones you will be able to, it look great and very effective. The timber ones you won’t be able to as they have a groove underneath.

  2. Hello,

    Any suggestions on how to straighten out some of the composite foundation beams? Few arrived bowed and I would like to straighten them up before the install starts.

    Cheers, Nedo

    • Those beams can be a pain sometimes, a hint of heat and they will bend if not kept straight. The good thing is though they are quite plyable, if you turn them against the bend they have developed they will quickly go back again especially if left out in the sun. They can though also be bent to shape during installation if necessary.

  3. Hi Richard

    Im going to be buying the Justine log cabin and placing on a eco deck plastic/gravel base.
    Should I put a DPM between the plastic base and the foundation.?
    I’m going for the standard foundation beams.


  4. I am researching the requirements for a possible purchase of a Laula log cabin 4.3m x 4.3m. I will be using it as a workshop and store and will be siting it on a concrete base with composite foundation beams. My question is if a put a DPM under the foundation beams with a silicone bead under the DPM and under the foundation beam. I will be fitting floor insulation, how does the under floor breath. I am conscious that any water getting under the floor would be trapped and cause damp and mould.
    Could you also forward me any drawings for this cabin for my base prep.

    • If the base is made to the footprint of the building, is straight, square and level there should not be a cause for water to find itself underneath. All the buildings pages will show the footprint of the cabin so in the case of the Laula the ideal base would be 4.10m x 4.10m.

  5. Hi Richard, from another Richard. We’re eagerly awaiting arrival of our Inglund log cabin in 2 weeks time. I’m building a timber frame base to support it and would like to deck the area in front. With the additional 35mm height of the deck boards is there sufficient clearance for the doors to open without using the foundation beams or should I install them anyway?
    Also, the pictures show the right hand door as having the handle. Would I be right to assume that this can’t be swapped over?

    • With that additional height I don’t think there will be enough clearance. Instead of the foundation beams you could use your decking boards, cut down to match the width of a log and use that, it would then bring the building up to the same level and finish it off nicely.

  6. Richard, if i’m building my cabin on to a ground screw foundation that is complete with 150mm timbers, do i need to use the supplied foundation beams or can i put the first layer of logs straight on to the 150mm timber frame foundation that is supported by the ground screws? I was thinking to place 150mm insulation in the timber frame foundation atop the ground screws then lay the T&G flooring directly on to this and not use the floor kit framing supplied with the Lauren? Would this work? If i use the foundation beams on top of the timber framing supplied by the ground screw folks, i would then have to use the floor kit to prevent a step down into the cabin, this would mean another 40mm of insulation. What’s your thoughts?

  7. Hi and thanks for all your invaluable information. I have a reasonably level concrete base. To git it perfectly level would you think that bedding the foundation beams on an thin layer of mortar would be ok. I plan to possibly use your recommended slithers of timber but I’m wondering if this method would be usable. Thanks.

  8. Should I screw the first layer of logs to the composite foundation? I see instructions about screwing the first layer to the timber foundation but what about the plastic composite foundation please?

    • It’s always a good idea to fix the first layer to the foundations as it helps with building stability and more importantly with installation in keeping it square. If you find the composite tough to screw you can drill a pilot hole first.

  9. having recently built a cabin and used the composite ground beams I would recommend that for future people ensure that the base they fit to is the exact size of the exterior of the cabin as I have experienced major water ingress under the ground beams due to the base being bigger than the floor size. this has been resolved by tanking the interior of the cabin prior to putting the floor down.
    the cabin is excellent and providing a great garden office space, very pleased.

  10. Hi, just wondering if my floor joists should be the same height as the foundation beam, the composite beam being 35mm high, isn’t a very standard size for finding floor joists ?

    • The floor joists can be any size you would like them to be, if they are taller than the foundation beam then these will first go around the perimeter of the inside of the building. When considering the floor thickness, insulation thickness and floor joists it is better to decide these against the door threshold height.

  11. Hi Richard, do you have to screw in the first log to the foundation beam? We are 3 levels up, have pre-treated the logs and realised we forgot to screw in the first log! Will it still be ok to carry on?!! If not then is there an alternative like screwing a nail in from the side as I am concerned about taking the logs apart and damaging them!! Thank you for your time

    • You don’t specifically have to but it does help with keeping the building square. It’s also good to screw down the door threshold and either side. If you haven’t it’s not a worry. You can either leave it as is or screw through at an angle. The screw head can then be hidden behind the skirting board or use a little wood filler to hide it outside.

  12. Hello,

    Thanks for all the information here – I have a follow up question though – do the foundation beams need to be treated with timber preservative too, or is the protection they come with sufficient? (I am using the CareFree protect that I bought with the cabin from you for the rest of the build.)



    • The foundation beams Tuin supply are either tanalised wood, hardwood or plastic / composite material. The tanalised beams do not really need treating but I find they do look nicer when painted. The hardwood beams will need oiling on a regular basis to keep the rich colour. The plastic do not need anything. With all of them it is a good idea to put a damp proof course underneath them to protect against damp. The payer of plastic also helps to seal them when on a rough surface.

  13. Hi Richard. I am considering a large log cabin (9.3m x 4.0m) in my garden. I was looking at the concrete foundation beams. It says on the website the following ” A great, ergonomic way to create a sturdy foundation for garden buildings without the need for a concrete or paving slab base. ” This implies that you would only have foundation under the beam – and then perhaps a sand base in the centre (to take the weight of the floor) – rather than a large slab of concrete. Or have i read this wrong?

    • You can use the concrete foundation beams on a bed of sand or sand and cement as you would a paving slab. so long of course the ground below is free from subsidence. You can also use paving slabs across the whole base making piers to support the floor joists. There is more ideas on bases here: Bases for log cabins

  14. I treated the wood with two coats of Cuprinol Preservative prior to construction but now the joints are really tight and result in damage in some instances when putting together. Probably not a good idea to treat the joints

  15. Hi Richard,

    If I am placing the Aiste cabin at 2.8 x 4.8m on a concrete base with integrated DPM of the same dimensions, do I still need the foundation beams? After all, the first beam of the cabin shouldn’t ever be sitting in water.

    Trying to avoid the extra height of the foundation beams as that’ll mean I can then add roof insulation!


    • In Europe they don’t tend to use foundation beams at all and will place the whole building on their bases. In the UK we tend to be buckles and braces just in case. But, as long as you are protecting the first log from damp and it’s never go to sit in pools of water then it should not be a problem. If you think there is any risk of the log sitting in water where it seals against the DPM and base I would also apply a bead of silicone or similar type of sealant.

  16. hi am wonder could you please help what is the required timber for a raised foundation about 2 to 3 feet above the ground and what distance the poles/concrete piers can be apart for your ardee 70mm log cabin as i bought this second hand but it was on a concrete slab previous

  17. Hello I have a patch of bare earth and am intending to buy a 5 x 4 Annabel home office cabin. Can this be built straight onto levelled flattened earth with the standard foundation beams or is it essential to build a base and if so what do you recommend for this model

    • If the base is level and fits the building and of course is free from subsidence over the lifetime of the building it should be fine. With paving slabs, if they are not to the footprint of the building, you will have to consider how you seal against water ingress as the base.

  18. Hi,

    Do i need to secure the foundation beams to my concrete base with fixings? or will the weight of the cabin stop the foundation beams from moving?

    • It is not normally necessary to fix the foundation beams to a concrete base. This of course does depend on your location, if you are in a very, very exposed location where high winds are experienced it would be a good idea to do so.

      If you are using a timber frame base i would recommend fixing them to the frame base.

      • Hello Richard, I am about to build my Stian log cabin, and have already completed a timber frame to support it, as per your great instructions. If the foundation beams (I use composite) are to be fixed to the timber frame as you recommend in this reply, would that not impact the Log cabins ability to expand/contract with weather movements? Br.

        • You don’t necessarily need to use foundation beams with a timber frame base as their task has already been accomplished by the base itself. However, using the profiled beams does provide a nice lip for aesthetics and easy draining. Fixing the foundation to the timber base will have no effect at all on the expansion of the logs. These expand width ways, and very minimally length ways. It is a good idea to also fix the first log to the foundation beam or base. No other wall logs should be fixed at all other than the roof purlins fixed to the top wall logs and of course roof board nails into the top log.

  19. Hi Richard, I’m also putting our cabin on a new deck especially designed to take it (load etc). Quick question, as this is going straight on the treated deck I was not planning on using foundation boards. In this case should I still screw the first log directly to the deck as you would if using foundation boards? I’m guessing I need to doubly make sure it is square as obviously can’t adjust at row 5! Thanks.

    • If you’re using decking you do not need to use the foundation beams if you do not want to. It is a good idea to fix the first log to the base as this will help to keep the building square as you build it.

  20. I have a decking base which was meant for a Spa room. As this project did not go ahead would this base be suitable for a corner cabin?

  21. hi i ordered composite beam. Do i fix the beam to the slab with a bead of sealent underneath and then fix the half log to the beam? also would you recomend sealing the inside of the beam and also the outer bottom of the beam

    • Thank you for your comment, it is though better to email us for a quicker response.

      Whether you choose to seal the beam is up to you and the quality / smoothness of the base. I do like to use a DPC under all foundations as this helps to seal, however, if you have a rough base that is larger than the footprint you will need to further seal the foundations.

  22. Why would you buy profiled beams if they don’t add any extra longevity ? Surely the standard ones would look same as standard profile one ?

    • You are quite correct, the choice of foundation beam is not based on longevity, it is a decision based on aesthetics. The standard square beam is fine but does not present the building as well as the profiled ones. Of course the composite ones will last for ever but with that being said I have never had to replace any beam in all the years I have been building log cabins.

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