Construction Materials & Methods

Our philosophy towards construction is design and build without compromise; using the best proven techniques and materials available to achieve the highest quality standards. Our ethos is to be the best in class, Park Home and Holiday Lodge manufacturer. This we always strive to achieve through a relentless pursuit of improvement and product development.

This summary is intended to inform you of some of the techniques and materials we use and why this is important within the manufacture of our homes. We want you to understand the difference with a Lissett Home.

Timber

Timber is still the world's most versatile and adaptable construction material and fundamental to the construction of our homes. We take the sourcing of our timber extremely seriously. We ensure it all comes from sustainable sources and that our suppliers are approved by the Forest Stewardship Council.

Our timber is slow grown Nordic red and white wood, from Finland and Sweden. The specification of the timber is chosen carefully to match its purpose and is kiln dried to 16%.

The significance of slow grown timber from these areas is the strength and the quality of the timber. It is all rated as top class and has the associated low level of knots and reduced size of knots. The cell structure of the timber is dense, making it heavier than other lower quality sources of timber. Our floor joists are vac/vac treated. This is timber which has been impregnated with VACSOL Aqua timber preservative under rigidly controlled conditions in a double vacuum/low pressure plant (Vac-Vac plant). Here the timber is placed in a tank and firstly a vacuum is applied to suck out all excess water from the timber. Then the preservative is added, and finally it is pressurised, forcing the preservative deep into the timber. VACSOL Aqua is a waterborne timber preservative formulation having fungicidal and insecticidal properties. We use the treatment on our joists to ensure complete peace of mind in a job well done that will last and last.

Insulation

There has never been greater pressure for dwellings to improve their thermal performance, with strict targets set by UK Government and passed through The Climate Change Act in 2008.

Park Homes and Holiday Lodges are currently manufactured to a British Standard, BS3632.

The insulation standards and thermal performance standards of BS3632 is significantly below that of current building regulations. Many manufacturers of Park Homes and Holiday Lodges choose to just meet those standards as outlined by BS3632. Lissett only construct Park Homes and Holiday lodges far in excess of the BS3632 and in excess of current building regulations which require much higher standards in both insulation and performance of heating appliances.

What is a U Value? (Unit W/m²k)

A U value is the rate of heat transfer per square metre of a structure i.e. the wall, roof or floor. The lower this figure is the better as this means there is less heat transfer. The U value is calculated by evaluating the insulation effect of the component parts of the building's structure.

What is thermal resistance? (known commonly as "R value" - unit m²k/W)

Thermal resistance is a measure of the amount of resistance to heat transfer a material of a given thickness provides. Simply it is a measure of how much insulation is provided.

What is air permeability? (Unit is m³/hm² (@50Pa))

The air permeability of a building measures the build quality of the envelope. Air permeability means uncontrolled air leakage through cracks and fissures (even microscopic cracks will leak air) in walls and roof. An air permeability test, is a standard test at 50 PA of pressure whilst considering the overall volume of the building and metres squared. A high air permeability indicates high loss of heat through air leakage, as a consequence within building regulations there is a minimum air leakage figure allowed.

All this translates into Lissett Homes selecting the best available materials and appliances to heat our homes and a building built to the highest quality standards. As a minimum we offer the following specification:

 

  Lissett Standard W/m²k BS3632 Standard W/m²k Current Building
Regulations Minimum W/m²k
Floors 0.18 0.5 0.25
Walls 0.32 0.5 0.3
Roof 0.18 0.3 0.16
Windows 1.2 (A Rated) 2.0 1.6 (C Rated)
Boiler A Band Not Specified Band B
Air permeability <3 m³/hm² (@50Pa) Not Specified <10 m³/hm² (@50Pa)

Sources: Building Regulations Approved Document Part L1A 2006 & revisions from 1st October 2010 BS3632:2005

The insulation we incorporate into our floors and wall is rigid polyurethane board (PU), some common trade names of the product include Kingspan and Xtratherm. It is currently one of the best insulating materials available per thickness of insulation. In addition to polyurethane board we utilise isowool when and where it is not practical to use polyurethane board e.g. some areas of the roof. Additional modern insulating materials include foil-backed breathable and waterproof membranes, which are incorporated into the construction.

Of course this is just the minimum specification on offer. At Lissett Homes you are able to improve the specification as far as you wish, and in fact many of our models also feature additional renewable energy features such as, solar thermal water heating and air source heat pumps.

Wall Construction

Our structural walls are constructed using a closed panel timber frame, with a thickness of 115mm - before any external cladding or rendering system. Although using a timber frame construction is common practice, our timber frame is inherently stronger than most other manufacturers. This is because we use high grade structural redwood timber within our framework and additional timber rails within the structure. To add to this strength we cover both faces of the framework by fixing and gluing structural external plywood. The result is a super strong structural wall, capable of supporting loads far in excess of required. Within these walls we pack the best insulating material available, polyurethane board. To the outside of these walls we cover with a water-proof and insulating membrane, the most advanced water-proofing and combined insulating material available.

The result is a tried and tested structural wall system — which we believe to the best in the industry.

Roof Construction

Our roof is constructed using trussed rafters to various designs to enable both flat ceiling roofs and vaulted (or cathedral type) roofs. The rafters have been certified by structural engineers and they are manufactured on site to tight quality standards.

The strength of the overall building comes from the strong tying between the roof, walls and floor. Our structure is all tied together using fixings, glue and cross-bonding with structural external plywood.

This results in an immensely strong structure capable of withstanding huge shear, strain and loads. It is with experience of building and transporting exceptionally large park homes and holiday lodges that we have understood the importance of an integrated structure. The difference to other manufacturers is we are able to consistently build the biggest park homes and holiday lodges in the industry. We are well respected by our long standing clients, who know they can rely of Lissett build quality.

Design

We design using 3 dimensional software to enable every detail to be scrutinised, ensuring the best use of available space within the construction. The advantage this offers is complete freedom and confidence in our design of bespoke homes, allowing you to experience this home whilst walking through it in a computer simulated model.

Chassis

Our construction starts with a robust hot rolled steel chassis, consisting of two large steel "C-sections" beams with high tensile strengthening beams. Our chassis are heavier than most manufacturers because our construction is heavier and more robust. Our chassis is manufactured in compliance to CP501 as required by the BS3636 (The British Standard for Residential Park Homes). Our chassis will last a lifetime and beyond.

Floor

Our floors are constructed using quality structural top class timber joists, vac/vac treated against fungicides and insects. It is integrated with the chassis, through tying every joist twice with mechanical bolts. Every timber is inspected prior to use and any timber not meeting strict quality inspection standards for straightness/knots is rejected. We integrate our joists in this way because it ensures the chassis behaves as one with the structure; creating an extremely strong foundation on which to build.

Precision Engineering

We are guided by lasers to ensure our construction is built to the tightest of tolerances. Constructing in modular requires skill, experience and accuracy. Lasers help this process and enable us to check and consistently measure more.

The result is a construction built far more precisely than any modern house builder.

Our Construction in Summary

Our construction is comparatively heavier than most of our competitors because our chassis is more substantial, we use more timber, our timber is often higher grade and denser and we use more insulation. Our construction is precision engineered and tied together to make the strongest and best insulated construction possible. The result is a construction which is built to a much higher quality than most other manufacturers and one which is built to last.