Bog mats: a specifier's guide to sizing, timber grade and hire versus buy

By George | September 2026 | 6 min read

 

A bog mat is specified by three variables: length, thickness and timber grade. Get them right for the load and the ground conditions, and you avoid both overpaying and under-engineering. Get one wrong and you either send a truck home overweight or you hire Ekki for a job that beech would have done at a fifth of the cost. This guide gives the thresholds, the numbers and the hire-versus-buy arithmetic behind each choice.

 

Where a bog mat sits, and where it doesn't

Bog mat, timber mat and crane mat are three names for the same product. In the UK trade, bog mat is the term that stuck.

The product it gets confused with is the road plate, and the confusion costs time. A road plate, sometimes called a trench plate, is steel, typically 19mm thick (25mm in newer specifications), and its job is to span a trench. It bridges a hole; it does not spread a load across soft ground.

HDPE ground mats occupy the middle ground. At 8mm to 40mm, with 15mm the most common, they suit lighter work: temporary haul roads over a Type 1 sub-base, event car parks, footfall areas where ground protection matters but crane loads do not.

Bog mats are the heavy end of the range. They go where cranes and heavy HGVs need to cross ground that would otherwise swallow them. Timber works on wet ground in a way HDPE or steel cannot.

"Bog mats are able to absorb water and therefore when they sit in the water or sit in particularly wet land, instead of the mats being continually driven into the ground, they attain a kind of buoyancy and they're much better at holding the weight and spreading the weight."

That flexibility also lets a mat conform to uneven ground rather than bridging it, which is why timber remains the material of choice despite the handling weight it brings with it.

 

The three variables that decide the mat

Three variables specify a bog mat: length, thickness and timber. Width is fixed at one metre as standard, so it rarely needs a decision, though bespoke widths and other bespoke sizing are available if a particular job demands them.

Length runs from three to six metres in the mainstream market. Roughly 70% of UK rental fleet stock sits in the five-metre range. The reason is practical: a longer mat covers more ground per lift, which means fewer mats to move and faster road-building across a site. If you are assembling a fleet and the choice is between four and five metres, pay the difference. The five-metre mat works on the jobs the four-metre would have covered, and on the ones it would not.

Thickness has a clear default. Most mainstream bog mats are 150mm, which the trade still quotes as six inches. Hire fleets typically run from 100mm to 200mm, with 80mm and 400mm mats made to order. Unless you have a specific reason to go thinner or thicker, 5m x 1m x 150mm is where you start.

Timber is the variable with the most consequence for cost, and it interacts with thickness. A 150mm European hardwood mat can match the weight-loading of a 100mm Ekki mat on many jobs, which means thickness and timber are not independent choices. Choose the right timber and you can often step down on thickness; choose the wrong one and you either over-spec the fleet or under-deliver on the load.

 

Timber grade: European hardwood, tropical mix and Ekki

Three timber grades cover almost every bog mat job, and they are not interchangeable on cost or performance. 

European hardwood, most commonly beech and occasionally oak from Eastern European mills, is the standard choice. It sits in the D30 to D40 strength class range (per EN 338, the European standard for timber strength classes), which is more than adequate for most infrastructure and groundworks. It takes the load, it conforms to uneven ground, and it is cost-effective. What it is not is a long-term plant investment: under heavy, repeated use in wet conditions, expect a service life measured in a few years rather than a decade. Plan around that rather than treat it as a defect.

Okan and Dabema, the two species most commonly supplied as a tropical hardwood mix, sit in the middle of the range at around D50 to D60 under EN 338, and are typically processed through mills in Germany and the Netherlands. They offer more strength and better rot resistance than European hardwood, and they suit jobs where the ground conditions or loading are severe enough to stress a D40 mat repeatedly.

Ekki bog mats, also known as Azobé, are the top of the range. This African timber sits at D60 and above, with a very high breaking point and very high resistance to rot, which makes it the right choice for prolonged exposure to standing water or the heaviest crane loads. It costs three to five times the price of a European hardwood mat of the same dimensions. Supply is constrained by export restrictions out of West Africa, and that constraint is structural rather than cyclical.

The practical problem is that Ekki has become a generic term the way Hoover did for vacuum cleaners.

"Some people do use Eki mats or Azobé mat just as a term for bog mats, it's almost become the vacuum hoover situation."

If your spec or your client says "Ekki mat", confirm whether Ekki is actually required or whether European hardwood will carry the load. In most cases it will, and the saving is substantial. Where European hardwood bog mat genuinely meets the requirement, specifying Ekki by name is the fastest way to triple the mat cost for no site benefit.

 

Quick reference: timber, strength and cost

Timber	Strength class	Relative cost	Typical use
European hardwood (beech / oak)	D30 to D40	Baseline	Mainstream infrastructure and groundworks; expect a few years under heavy repeated use
Tropical hardwood (Okan / Dabema)	D50 to D60	Mid-range	Heavier loads or jobs where longer service life matters
Ekki (Azobé)	D60+	3 to 5 times baseline	Maximum load, prolonged standing water, long-term deployment

 

Strength classes follow EN 338; the D-numbers in the table refer to that standard throughout.

 

Hire, buy or lease: the week thresholds

Duration is the fourth variable, and it turns the procurement decision into arithmetic. The rule of thumb for European hardwood is simple enough to remember on site.

"Anything under 15 weeks, I don't think that's a consideration, you definitely hire it. Anything from 15 weeks up to a year, then there's a consideration to buy. For a year, you're probably going to buy the mat in terms of cost effectiveness."

Below 15 weeks, bog mat hire wins. You avoid capital outlay, storage and the condition risk on return. Between 15 weeks and a year, buying enters the frame, and the calculation depends on cash flow, how payments release across the programme and whether a lease structure fits the contract. Beyond a year, buying outright is almost always cheaper than cumulative hire costs.

Ekki is a different decision. Hire in almost every case. The purchase price is three to five times higher than European hardwood, which pushes the breakeven point well beyond what most projects run to. The exceptions are narrow: a plant division with a repetitive need for the same specification, or a rehire company assembling a fleet. Everyone else hires. 

If you are buying, agree an indicative buyback price at the point of purchase. HERMEQ buys back mats it has sold subject to condition, and knowing the exit price before you commit changes the project cost calculation. Get the guide figure in writing early rather than negotiating under pressure when the job finishes. 

For rehire buyers building a fleet, buy the specification with the widest application. A five-metre mat works on every job a four-metre would cover and on the jobs it would not, so the longer length earns its premium across the life of the fleet.

 

Don't over-spec

Over-specification costs money twice: once on the mat itself, and again every time you move it. Thicker mats are heavier mats, which means fewer per load, more vehicle runs and a higher transport bill across the life of the job. Specifying 200mm when 150mm meets the load adds cost on every leg without adding site benefit.

"These mats are very heavy, so you don't necessarily want to over-spec this."

The same logic applies to timber. If the ground and the load are within what European hardwood delivers, specifying Ekki triples the bill for no gain. Before you confirm the order, ask one question: does the job require Ekki, or does it require a bog mat? In most cases it is the latter, and European hardwood is the answer.

 

How they're built, and what to look at before you sign off

A bog mat is built from individual timbers trimmed to a consistent cross-section, end-sawn to equal length, then bolted through drilled holes at each end and at one or more points along the middle. The number of mid-bolts increases with length, but the principle is the same across the range: the bolts hold the assembly together under lateral stress, and their quality is one of the clearest markers of a better mill. Undersized or soft bolts shear under repeated loading and chain-drag, and replacing them on site is a job nobody plans for.

Chamfered edges are the other thing to check. Reducing the 90-degree corner on each timber sounds minor, but it matters in service: sharp corners are where breakage starts, both during handling and once the mat is under vehicle traffic. A mill that chamfers its edges is paying attention to the parts of construction the specification sheet will not capture. 

Lifting points are built into every mat as cutouts near each end, each one exposing a bolt that the crane hook or drag chain attaches to. Inspect them before every move. A bent or damaged lifting point is a load-security risk that grounds the mat until it is replaced. If you are taking mats on hire, make this check part of your acceptance procedure on delivery.

 

Handling, weight-when-wet and the trench-plate trap

Move bog mats with a crane, a Moffett forklift or a telehandler, using chains attached to the lifting points at each end. That is the method, and the lifting points are there for exactly that purpose. If you are stacking mats on site for later use, leave timber bearers between layers so a telehandler or forklift can get underneath without needing chains at all. It saves time on every move.

The weight problem nobody warns you about is what happens after the mat has been sitting in water for a week. A mat that left the yard dry absorbs a significant amount of water in service, and that weight is still in the timber when it goes back on the truck. Load your return vehicles based on what the mats weigh wet, not what the spec sheet says. Getting this wrong means a vehicle over its legal limit before it leaves the site. 

On hire, damage charges should not be a serious concern if the mats are used as intended. Protect yourself anyway: photograph the condition of every mat when it arrives, and report any pre-existing damage to the hire company before the mats go into use. That record is what resolves any dispute at the end of the job without argument. 

Finally, the trench-plate trap. Bog mats are not rated to bridge holes. The vast majority of the underside needs ground contact to distribute the load, and a mat spanning a gap will break under vehicle weight. If you need to cover a trench or an excavation, that is a road plate job. Using a bog mat in its place is a failure waiting to happen.

 

The default choice

For most UK infrastructure jobs, the default is a 5m x 1m x 150mm European hardwood mat. Hire it if the programme runs under 15 weeks. Between 15 weeks and a year, run the buy calculation. Beyond a year, buy outright and agree a buyback price at the point of sale.

Move to Ekki only when load, prolonged wet conditions or service life genuinely demand it. When you do, hire it. The purchase price makes ownership the right answer for almost nobody.

 

 

FAQ

Are Ekki mats and bog mats the same thing?

Ekki is a timber species used to make bog mats, not a separate product category. A bog mat built from Ekki (Azobé) is still a bog mat. The distinction matters for cost and load capacity: Ekki sits at the top of the timber grade range, roughly three to five times the price of a European hardwood mat, and is specified where the hardwood grades cannot carry the load or the service life demanded.

 

Can I use a bog mat to cover a hole or trench?

No. A bog mat is not a road plate and should not be used to span a trench or open excavation where vehicles will cross. Road plates are engineered for point-load spanning; bog mats are built to distribute load across soft or uneven ground. Using a bog mat as a bridge introduces bending forces it is not designed to resist, and the bolted-timber construction can fail without visible warning.

 

How much heavier is a bog mat when wet?

A saturated bog mat weighs significantly more than its dry rating, because timber absorbs water throughout its cross-section during site use. The practical problem arises on collection: mats that went out at a known dry weight can return heavy enough to push a loaded truck over its legal payload. Account for water uptake when calculating return loads, and weigh mats if there is any doubt about the vehicle's margin.